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Diffstat (limited to 'js/src/regexp/regexp-compiler.cc')
| -rw-r--r-- | js/src/regexp/regexp-compiler.cc | 3834 |
1 files changed, 3834 insertions, 0 deletions
diff --git a/js/src/regexp/regexp-compiler.cc b/js/src/regexp/regexp-compiler.cc new file mode 100644 index 0000000000..9a2aa30dcc --- /dev/null +++ b/js/src/regexp/regexp-compiler.cc @@ -0,0 +1,3834 @@ +// Copyright 2019 the V8 project authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#include "regexp/regexp-compiler.h" + +#include "regexp/regexp-macro-assembler-arch.h" +#include "regexp/regexp-macro-assembler-tracer.h" + +#ifdef V8_INTL_SUPPORT +#include "unicode/locid.h" +#include "unicode/uniset.h" +#include "unicode/utypes.h" +#endif // V8_INTL_SUPPORT + +namespace v8 { +namespace internal { + +using namespace regexp_compiler_constants; // NOLINT(build/namespaces) + +// ------------------------------------------------------------------- +// Implementation of the Irregexp regular expression engine. +// +// The Irregexp regular expression engine is intended to be a complete +// implementation of ECMAScript regular expressions. It generates either +// bytecodes or native code. + +// The Irregexp regexp engine is structured in three steps. +// 1) The parser generates an abstract syntax tree. See ast.cc. +// 2) From the AST a node network is created. The nodes are all +// subclasses of RegExpNode. The nodes represent states when +// executing a regular expression. Several optimizations are +// performed on the node network. +// 3) From the nodes we generate either byte codes or native code +// that can actually execute the regular expression (perform +// the search). The code generation step is described in more +// detail below. + +// Code generation. +// +// The nodes are divided into four main categories. +// * Choice nodes +// These represent places where the regular expression can +// match in more than one way. For example on entry to an +// alternation (foo|bar) or a repetition (*, +, ? or {}). +// * Action nodes +// These represent places where some action should be +// performed. Examples include recording the current position +// in the input string to a register (in order to implement +// captures) or other actions on register for example in order +// to implement the counters needed for {} repetitions. +// * Matching nodes +// These attempt to match some element part of the input string. +// Examples of elements include character classes, plain strings +// or back references. +// * End nodes +// These are used to implement the actions required on finding +// a successful match or failing to find a match. +// +// The code generated (whether as byte codes or native code) maintains +// some state as it runs. This consists of the following elements: +// +// * The capture registers. Used for string captures. +// * Other registers. Used for counters etc. +// * The current position. +// * The stack of backtracking information. Used when a matching node +// fails to find a match and needs to try an alternative. +// +// Conceptual regular expression execution model: +// +// There is a simple conceptual model of regular expression execution +// which will be presented first. The actual code generated is a more +// efficient simulation of the simple conceptual model: +// +// * Choice nodes are implemented as follows: +// For each choice except the last { +// push current position +// push backtrack code location +// <generate code to test for choice> +// backtrack code location: +// pop current position +// } +// <generate code to test for last choice> +// +// * Actions nodes are generated as follows +// <push affected registers on backtrack stack> +// <generate code to perform action> +// push backtrack code location +// <generate code to test for following nodes> +// backtrack code location: +// <pop affected registers to restore their state> +// <pop backtrack location from stack and go to it> +// +// * Matching nodes are generated as follows: +// if input string matches at current position +// update current position +// <generate code to test for following nodes> +// else +// <pop backtrack location from stack and go to it> +// +// Thus it can be seen that the current position is saved and restored +// by the choice nodes, whereas the registers are saved and restored by +// by the action nodes that manipulate them. +// +// The other interesting aspect of this model is that nodes are generated +// at the point where they are needed by a recursive call to Emit(). If +// the node has already been code generated then the Emit() call will +// generate a jump to the previously generated code instead. In order to +// limit recursion it is possible for the Emit() function to put the node +// on a work list for later generation and instead generate a jump. The +// destination of the jump is resolved later when the code is generated. +// +// Actual regular expression code generation. +// +// Code generation is actually more complicated than the above. In order +// to improve the efficiency of the generated code some optimizations are +// performed +// +// * Choice nodes have 1-character lookahead. +// A choice node looks at the following character and eliminates some of +// the choices immediately based on that character. This is not yet +// implemented. +// * Simple greedy loops store reduced backtracking information. +// A quantifier like /.*foo/m will greedily match the whole input. It will +// then need to backtrack to a point where it can match "foo". The naive +// implementation of this would push each character position onto the +// backtracking stack, then pop them off one by one. This would use space +// proportional to the length of the input string. However since the "." +// can only match in one way and always has a constant length (in this case +// of 1) it suffices to store the current position on the top of the stack +// once. Matching now becomes merely incrementing the current position and +// backtracking becomes decrementing the current position and checking the +// result against the stored current position. This is faster and saves +// space. +// * The current state is virtualized. +// This is used to defer expensive operations until it is clear that they +// are needed and to generate code for a node more than once, allowing +// specialized an efficient versions of the code to be created. This is +// explained in the section below. +// +// Execution state virtualization. +// +// Instead of emitting code, nodes that manipulate the state can record their +// manipulation in an object called the Trace. The Trace object can record a +// current position offset, an optional backtrack code location on the top of +// the virtualized backtrack stack and some register changes. When a node is +// to be emitted it can flush the Trace or update it. Flushing the Trace +// will emit code to bring the actual state into line with the virtual state. +// Avoiding flushing the state can postpone some work (e.g. updates of capture +// registers). Postponing work can save time when executing the regular +// expression since it may be found that the work never has to be done as a +// failure to match can occur. In addition it is much faster to jump to a +// known backtrack code location than it is to pop an unknown backtrack +// location from the stack and jump there. +// +// The virtual state found in the Trace affects code generation. For example +// the virtual state contains the difference between the actual current +// position and the virtual current position, and matching code needs to use +// this offset to attempt a match in the correct location of the input +// string. Therefore code generated for a non-trivial trace is specialized +// to that trace. The code generator therefore has the ability to generate +// code for each node several times. In order to limit the size of the +// generated code there is an arbitrary limit on how many specialized sets of +// code may be generated for a given node. If the limit is reached, the +// trace is flushed and a generic version of the code for a node is emitted. +// This is subsequently used for that node. The code emitted for non-generic +// trace is not recorded in the node and so it cannot currently be reused in +// the event that code generation is requested for an identical trace. + +void RegExpTree::AppendToText(RegExpText* text, Zone* zone) { UNREACHABLE(); } + +void RegExpAtom::AppendToText(RegExpText* text, Zone* zone) { + text->AddElement(TextElement::Atom(this), zone); +} + +void RegExpCharacterClass::AppendToText(RegExpText* text, Zone* zone) { + text->AddElement(TextElement::CharClass(this), zone); +} + +void RegExpText::AppendToText(RegExpText* text, Zone* zone) { + for (int i = 0; i < elements()->length(); i++) + text->AddElement(elements()->at(i), zone); +} + +TextElement TextElement::Atom(RegExpAtom* atom) { + return TextElement(ATOM, atom); +} + +TextElement TextElement::CharClass(RegExpCharacterClass* char_class) { + return TextElement(CHAR_CLASS, char_class); +} + +int TextElement::length() const { + switch (text_type()) { + case ATOM: + return atom()->length(); + + case CHAR_CLASS: + return 1; + } + UNREACHABLE(); +} + +class RecursionCheck { + public: + explicit RecursionCheck(RegExpCompiler* compiler) : compiler_(compiler) { + compiler->IncrementRecursionDepth(); + } + ~RecursionCheck() { compiler_->DecrementRecursionDepth(); } + + private: + RegExpCompiler* compiler_; +}; + +// Attempts to compile the regexp using an Irregexp code generator. Returns +// a fixed array or a null handle depending on whether it succeeded. +RegExpCompiler::RegExpCompiler(Isolate* isolate, Zone* zone, int capture_count, + bool one_byte) + : next_register_(2 * (capture_count + 1)), + unicode_lookaround_stack_register_(kNoRegister), + unicode_lookaround_position_register_(kNoRegister), + work_list_(nullptr), + recursion_depth_(0), + one_byte_(one_byte), + reg_exp_too_big_(false), + limiting_recursion_(false), + optimize_(FLAG_regexp_optimization), + read_backward_(false), + current_expansion_factor_(1), + frequency_collator_(), + isolate_(isolate), + zone_(zone) { + accept_ = new (zone) EndNode(EndNode::ACCEPT, zone); + DCHECK_GE(RegExpMacroAssembler::kMaxRegister, next_register_ - 1); +} + +RegExpCompiler::CompilationResult RegExpCompiler::Assemble( + Isolate* isolate, RegExpMacroAssembler* macro_assembler, RegExpNode* start, + int capture_count, Handle<String> pattern) { +#ifdef DEBUG + if (FLAG_trace_regexp_assembler) + macro_assembler_ = new RegExpMacroAssemblerTracer(isolate, macro_assembler); + else +#endif + macro_assembler_ = macro_assembler; + + std::vector<RegExpNode*> work_list; + work_list_ = &work_list; + Label fail; + macro_assembler_->PushBacktrack(&fail); + Trace new_trace; + start->Emit(this, &new_trace); + macro_assembler_->Bind(&fail); + macro_assembler_->Fail(); + while (!work_list.empty()) { + RegExpNode* node = work_list.back(); + work_list.pop_back(); + node->set_on_work_list(false); + if (!node->label()->is_bound()) node->Emit(this, &new_trace); + } + if (reg_exp_too_big_) { + macro_assembler_->AbortedCodeGeneration(); + return CompilationResult::RegExpTooBig(); + } + + Handle<HeapObject> code = macro_assembler_->GetCode(pattern); + isolate->IncreaseTotalRegexpCodeGenerated(code->Size()); + work_list_ = nullptr; + +#ifdef DEBUG + if (FLAG_trace_regexp_assembler) { + delete macro_assembler_; + } +#endif + return {*code, next_register_}; +} + +bool Trace::DeferredAction::Mentions(int that) { + if (action_type() == ActionNode::CLEAR_CAPTURES) { + Interval range = static_cast<DeferredClearCaptures*>(this)->range(); + return range.Contains(that); + } else { + return reg() == that; + } +} + +bool Trace::mentions_reg(int reg) { + for (DeferredAction* action = actions_; action != nullptr; + action = action->next()) { + if (action->Mentions(reg)) return true; + } + return false; +} + +bool Trace::GetStoredPosition(int reg, int* cp_offset) { + DCHECK_EQ(0, *cp_offset); + for (DeferredAction* action = actions_; action != nullptr; + action = action->next()) { + if (action->Mentions(reg)) { + if (action->action_type() == ActionNode::STORE_POSITION) { + *cp_offset = static_cast<DeferredCapture*>(action)->cp_offset(); + return true; + } else { + return false; + } + } + } + return false; +} + +// A (dynamically-sized) set of unsigned integers that behaves especially well +// on small integers (< kFirstLimit). May do zone-allocation. +class DynamicBitSet : public ZoneObject { + public: + V8_EXPORT_PRIVATE bool Get(unsigned value) const { + if (value < kFirstLimit) { + return (first_ & (1 << value)) != 0; + } else if (remaining_ == nullptr) { + return false; + } else { + return remaining_->Contains(value); + } + } + + // Destructively set a value in this set. + void Set(unsigned value, Zone* zone) { + if (value < kFirstLimit) { + first_ |= (1 << value); + } else { + if (remaining_ == nullptr) + remaining_ = new (zone) ZoneList<unsigned>(1, zone); + if (remaining_->is_empty() || !remaining_->Contains(value)) + remaining_->Add(value, zone); + } + } + + private: + static constexpr unsigned kFirstLimit = 32; + + uint32_t first_ = 0; + ZoneList<unsigned>* remaining_ = nullptr; +}; + +int Trace::FindAffectedRegisters(DynamicBitSet* affected_registers, + Zone* zone) { + int max_register = RegExpCompiler::kNoRegister; + for (DeferredAction* action = actions_; action != nullptr; + action = action->next()) { + if (action->action_type() == ActionNode::CLEAR_CAPTURES) { + Interval range = static_cast<DeferredClearCaptures*>(action)->range(); + for (int i = range.from(); i <= range.to(); i++) + affected_registers->Set(i, zone); + if (range.to() > max_register) max_register = range.to(); + } else { + affected_registers->Set(action->reg(), zone); + if (action->reg() > max_register) max_register = action->reg(); + } + } + return max_register; +} + +void Trace::RestoreAffectedRegisters(RegExpMacroAssembler* assembler, + int max_register, + const DynamicBitSet& registers_to_pop, + const DynamicBitSet& registers_to_clear) { + for (int reg = max_register; reg >= 0; reg--) { + if (registers_to_pop.Get(reg)) { + assembler->PopRegister(reg); + } else if (registers_to_clear.Get(reg)) { + int clear_to = reg; + while (reg > 0 && registers_to_clear.Get(reg - 1)) { + reg--; + } + assembler->ClearRegisters(reg, clear_to); + } + } +} + +void Trace::PerformDeferredActions(RegExpMacroAssembler* assembler, + int max_register, + const DynamicBitSet& affected_registers, + DynamicBitSet* registers_to_pop, + DynamicBitSet* registers_to_clear, + Zone* zone) { + // The "+1" is to avoid a push_limit of zero if stack_limit_slack() is 1. + const int push_limit = (assembler->stack_limit_slack() + 1) / 2; + + // Count pushes performed to force a stack limit check occasionally. + int pushes = 0; + + for (int reg = 0; reg <= max_register; reg++) { + if (!affected_registers.Get(reg)) { + continue; + } + + // The chronologically first deferred action in the trace + // is used to infer the action needed to restore a register + // to its previous state (or not, if it's safe to ignore it). + enum DeferredActionUndoType { IGNORE, RESTORE, CLEAR }; + DeferredActionUndoType undo_action = IGNORE; + + int value = 0; + bool absolute = false; + bool clear = false; + static const int kNoStore = kMinInt; + int store_position = kNoStore; + // This is a little tricky because we are scanning the actions in reverse + // historical order (newest first). + for (DeferredAction* action = actions_; action != nullptr; + action = action->next()) { + if (action->Mentions(reg)) { + switch (action->action_type()) { + case ActionNode::SET_REGISTER_FOR_LOOP: { + Trace::DeferredSetRegisterForLoop* psr = + static_cast<Trace::DeferredSetRegisterForLoop*>(action); + if (!absolute) { + value += psr->value(); + absolute = true; + } + // SET_REGISTER_FOR_LOOP is only used for newly introduced loop + // counters. They can have a significant previous value if they + // occur in a loop. TODO(lrn): Propagate this information, so + // we can set undo_action to IGNORE if we know there is no value to + // restore. + undo_action = RESTORE; + DCHECK_EQ(store_position, kNoStore); + DCHECK(!clear); + break; + } + case ActionNode::INCREMENT_REGISTER: + if (!absolute) { + value++; + } + DCHECK_EQ(store_position, kNoStore); + DCHECK(!clear); + undo_action = RESTORE; + break; + case ActionNode::STORE_POSITION: { + Trace::DeferredCapture* pc = + static_cast<Trace::DeferredCapture*>(action); + if (!clear && store_position == kNoStore) { + store_position = pc->cp_offset(); + } + + // For captures we know that stores and clears alternate. + // Other register, are never cleared, and if the occur + // inside a loop, they might be assigned more than once. + if (reg <= 1) { + // Registers zero and one, aka "capture zero", is + // always set correctly if we succeed. There is no + // need to undo a setting on backtrack, because we + // will set it again or fail. + undo_action = IGNORE; + } else { + undo_action = pc->is_capture() ? CLEAR : RESTORE; + } + DCHECK(!absolute); + DCHECK_EQ(value, 0); + break; + } + case ActionNode::CLEAR_CAPTURES: { + // Since we're scanning in reverse order, if we've already + // set the position we have to ignore historically earlier + // clearing operations. + if (store_position == kNoStore) { + clear = true; + } + undo_action = RESTORE; + DCHECK(!absolute); + DCHECK_EQ(value, 0); + break; + } + default: + UNREACHABLE(); + break; + } + } + } + // Prepare for the undo-action (e.g., push if it's going to be popped). + if (undo_action == RESTORE) { + pushes++; + RegExpMacroAssembler::StackCheckFlag stack_check = + RegExpMacroAssembler::kNoStackLimitCheck; + if (pushes == push_limit) { + stack_check = RegExpMacroAssembler::kCheckStackLimit; + pushes = 0; + } + + assembler->PushRegister(reg, stack_check); + registers_to_pop->Set(reg, zone); + } else if (undo_action == CLEAR) { + registers_to_clear->Set(reg, zone); + } + // Perform the chronologically last action (or accumulated increment) + // for the register. + if (store_position != kNoStore) { + assembler->WriteCurrentPositionToRegister(reg, store_position); + } else if (clear) { + assembler->ClearRegisters(reg, reg); + } else if (absolute) { + assembler->SetRegister(reg, value); + } else if (value != 0) { + assembler->AdvanceRegister(reg, value); + } + } +} + +// This is called as we come into a loop choice node and some other tricky +// nodes. It normalizes the state of the code generator to ensure we can +// generate generic code. +void Trace::Flush(RegExpCompiler* compiler, RegExpNode* successor) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + + DCHECK(!is_trivial()); + + if (actions_ == nullptr && backtrack() == nullptr) { + // Here we just have some deferred cp advances to fix and we are back to + // a normal situation. We may also have to forget some information gained + // through a quick check that was already performed. + if (cp_offset_ != 0) assembler->AdvanceCurrentPosition(cp_offset_); + // Create a new trivial state and generate the node with that. + Trace new_state; + successor->Emit(compiler, &new_state); + return; + } + + // Generate deferred actions here along with code to undo them again. + DynamicBitSet affected_registers; + + if (backtrack() != nullptr) { + // Here we have a concrete backtrack location. These are set up by choice + // nodes and so they indicate that we have a deferred save of the current + // position which we may need to emit here. + assembler->PushCurrentPosition(); + } + + int max_register = + FindAffectedRegisters(&affected_registers, compiler->zone()); + DynamicBitSet registers_to_pop; + DynamicBitSet registers_to_clear; + PerformDeferredActions(assembler, max_register, affected_registers, + ®isters_to_pop, ®isters_to_clear, + compiler->zone()); + if (cp_offset_ != 0) { + assembler->AdvanceCurrentPosition(cp_offset_); + } + + // Create a new trivial state and generate the node with that. + Label undo; + assembler->PushBacktrack(&undo); + if (successor->KeepRecursing(compiler)) { + Trace new_state; + successor->Emit(compiler, &new_state); + } else { + compiler->AddWork(successor); + assembler->GoTo(successor->label()); + } + + // On backtrack we need to restore state. + assembler->Bind(&undo); + RestoreAffectedRegisters(assembler, max_register, registers_to_pop, + registers_to_clear); + if (backtrack() == nullptr) { + assembler->Backtrack(); + } else { + assembler->PopCurrentPosition(); + assembler->GoTo(backtrack()); + } +} + +void NegativeSubmatchSuccess::Emit(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + + // Omit flushing the trace. We discard the entire stack frame anyway. + + if (!label()->is_bound()) { + // We are completely independent of the trace, since we ignore it, + // so this code can be used as the generic version. + assembler->Bind(label()); + } + + // Throw away everything on the backtrack stack since the start + // of the negative submatch and restore the character position. + assembler->ReadCurrentPositionFromRegister(current_position_register_); + assembler->ReadStackPointerFromRegister(stack_pointer_register_); + if (clear_capture_count_ > 0) { + // Clear any captures that might have been performed during the success + // of the body of the negative look-ahead. + int clear_capture_end = clear_capture_start_ + clear_capture_count_ - 1; + assembler->ClearRegisters(clear_capture_start_, clear_capture_end); + } + // Now that we have unwound the stack we find at the top of the stack the + // backtrack that the BeginSubmatch node got. + assembler->Backtrack(); +} + +void EndNode::Emit(RegExpCompiler* compiler, Trace* trace) { + if (!trace->is_trivial()) { + trace->Flush(compiler, this); + return; + } + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + if (!label()->is_bound()) { + assembler->Bind(label()); + } + switch (action_) { + case ACCEPT: + assembler->Succeed(); + return; + case BACKTRACK: + assembler->GoTo(trace->backtrack()); + return; + case NEGATIVE_SUBMATCH_SUCCESS: + // This case is handled in a different virtual method. + UNREACHABLE(); + } + UNIMPLEMENTED(); +} + +void GuardedAlternative::AddGuard(Guard* guard, Zone* zone) { + if (guards_ == nullptr) guards_ = new (zone) ZoneList<Guard*>(1, zone); + guards_->Add(guard, zone); +} + +ActionNode* ActionNode::SetRegisterForLoop(int reg, int val, + RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(SET_REGISTER_FOR_LOOP, on_success); + result->data_.u_store_register.reg = reg; + result->data_.u_store_register.value = val; + return result; +} + +ActionNode* ActionNode::IncrementRegister(int reg, RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(INCREMENT_REGISTER, on_success); + result->data_.u_increment_register.reg = reg; + return result; +} + +ActionNode* ActionNode::StorePosition(int reg, bool is_capture, + RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(STORE_POSITION, on_success); + result->data_.u_position_register.reg = reg; + result->data_.u_position_register.is_capture = is_capture; + return result; +} + +ActionNode* ActionNode::ClearCaptures(Interval range, RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(CLEAR_CAPTURES, on_success); + result->data_.u_clear_captures.range_from = range.from(); + result->data_.u_clear_captures.range_to = range.to(); + return result; +} + +ActionNode* ActionNode::BeginSubmatch(int stack_reg, int position_reg, + RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(BEGIN_SUBMATCH, on_success); + result->data_.u_submatch.stack_pointer_register = stack_reg; + result->data_.u_submatch.current_position_register = position_reg; + return result; +} + +ActionNode* ActionNode::PositiveSubmatchSuccess(int stack_reg, int position_reg, + int clear_register_count, + int clear_register_from, + RegExpNode* on_success) { + ActionNode* result = new (on_success->zone()) + ActionNode(POSITIVE_SUBMATCH_SUCCESS, on_success); + result->data_.u_submatch.stack_pointer_register = stack_reg; + result->data_.u_submatch.current_position_register = position_reg; + result->data_.u_submatch.clear_register_count = clear_register_count; + result->data_.u_submatch.clear_register_from = clear_register_from; + return result; +} + +ActionNode* ActionNode::EmptyMatchCheck(int start_register, + int repetition_register, + int repetition_limit, + RegExpNode* on_success) { + ActionNode* result = + new (on_success->zone()) ActionNode(EMPTY_MATCH_CHECK, on_success); + result->data_.u_empty_match_check.start_register = start_register; + result->data_.u_empty_match_check.repetition_register = repetition_register; + result->data_.u_empty_match_check.repetition_limit = repetition_limit; + return result; +} + +#define DEFINE_ACCEPT(Type) \ + void Type##Node::Accept(NodeVisitor* visitor) { visitor->Visit##Type(this); } +FOR_EACH_NODE_TYPE(DEFINE_ACCEPT) +#undef DEFINE_ACCEPT + +// ------------------------------------------------------------------- +// Emit code. + +void ChoiceNode::GenerateGuard(RegExpMacroAssembler* macro_assembler, + Guard* guard, Trace* trace) { + switch (guard->op()) { + case Guard::LT: + DCHECK(!trace->mentions_reg(guard->reg())); + macro_assembler->IfRegisterGE(guard->reg(), guard->value(), + trace->backtrack()); + break; + case Guard::GEQ: + DCHECK(!trace->mentions_reg(guard->reg())); + macro_assembler->IfRegisterLT(guard->reg(), guard->value(), + trace->backtrack()); + break; + } +} + +// Returns the number of characters in the equivalence class, omitting those +// that cannot occur in the source string because it is Latin1. +static int GetCaseIndependentLetters(Isolate* isolate, uc16 character, + bool one_byte_subject, + unibrow::uchar* letters, + int letter_length) { +#ifdef V8_INTL_SUPPORT + // Special case for U+017F which has upper case in ASCII range. + if (character == 0x017f) { + letters[0] = character; + return 1; + } + icu::UnicodeSet set; + set.add(character); + set = set.closeOver(USET_CASE_INSENSITIVE); + int32_t range_count = set.getRangeCount(); + int items = 0; + for (int32_t i = 0; i < range_count; i++) { + UChar32 start = set.getRangeStart(i); + UChar32 end = set.getRangeEnd(i); + CHECK(end - start + items <= letter_length); + // Only add to the output if character is not in ASCII range + // or the case equivalent character is in ASCII range. + // #sec-runtime-semantics-canonicalize-ch + // 3.g If the numeric value of ch ≥ 128 and the numeric value of cu < 128, + // return ch. + if (!((start >= 128) && (character < 128))) { + // No range have start and end span across code point 128. + DCHECK((start >= 128) == (end >= 128)); + for (UChar32 cu = start; cu <= end; cu++) { + if (one_byte_subject && cu > String::kMaxOneByteCharCode) break; + letters[items++] = (unibrow::uchar)(cu); + } + } + } + return items; +#else + int length = + isolate->jsregexp_uncanonicalize()->get(character, '\0', letters); + // Unibrow returns 0 or 1 for characters where case independence is + // trivial. + if (length == 0) { + letters[0] = character; + length = 1; + } + + if (one_byte_subject) { + int new_length = 0; + for (int i = 0; i < length; i++) { + if (letters[i] <= String::kMaxOneByteCharCode) { + letters[new_length++] = letters[i]; + } + } + length = new_length; + } + + return length; +#endif // V8_INTL_SUPPORT +} + +static inline bool EmitSimpleCharacter(Isolate* isolate, + RegExpCompiler* compiler, uc16 c, + Label* on_failure, int cp_offset, + bool check, bool preloaded) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + bool bound_checked = false; + if (!preloaded) { + assembler->LoadCurrentCharacter(cp_offset, on_failure, check); + bound_checked = true; + } + assembler->CheckNotCharacter(c, on_failure); + return bound_checked; +} + +// Only emits non-letters (things that don't have case). Only used for case +// independent matches. +static inline bool EmitAtomNonLetter(Isolate* isolate, RegExpCompiler* compiler, + uc16 c, Label* on_failure, int cp_offset, + bool check, bool preloaded) { + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + bool one_byte = compiler->one_byte(); + unibrow::uchar chars[4]; + int length = GetCaseIndependentLetters(isolate, c, one_byte, chars, 4); + if (length < 1) { + // This can't match. Must be an one-byte subject and a non-one-byte + // character. We do not need to do anything since the one-byte pass + // already handled this. + return false; // Bounds not checked. + } + bool checked = false; + // We handle the length > 1 case in a later pass. + if (length == 1) { + if (one_byte && c > String::kMaxOneByteCharCodeU) { + // Can't match - see above. + return false; // Bounds not checked. + } + if (!preloaded) { + macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check); + checked = check; + } + macro_assembler->CheckNotCharacter(c, on_failure); + } + return checked; +} + +static bool ShortCutEmitCharacterPair(RegExpMacroAssembler* macro_assembler, + bool one_byte, uc16 c1, uc16 c2, + Label* on_failure) { + uc16 char_mask; + if (one_byte) { + char_mask = String::kMaxOneByteCharCode; + } else { + char_mask = String::kMaxUtf16CodeUnit; + } + uc16 exor = c1 ^ c2; + // Check whether exor has only one bit set. + if (((exor - 1) & exor) == 0) { + // If c1 and c2 differ only by one bit. + // Ecma262UnCanonicalize always gives the highest number last. + DCHECK(c2 > c1); + uc16 mask = char_mask ^ exor; + macro_assembler->CheckNotCharacterAfterAnd(c1, mask, on_failure); + return true; + } + DCHECK(c2 > c1); + uc16 diff = c2 - c1; + if (((diff - 1) & diff) == 0 && c1 >= diff) { + // If the characters differ by 2^n but don't differ by one bit then + // subtract the difference from the found character, then do the or + // trick. We avoid the theoretical case where negative numbers are + // involved in order to simplify code generation. + uc16 mask = char_mask ^ diff; + macro_assembler->CheckNotCharacterAfterMinusAnd(c1 - diff, diff, mask, + on_failure); + return true; + } + return false; +} + +using EmitCharacterFunction = bool(Isolate* isolate, RegExpCompiler* compiler, + uc16 c, Label* on_failure, int cp_offset, + bool check, bool preloaded); + +// Only emits letters (things that have case). Only used for case independent +// matches. +static inline bool EmitAtomLetter(Isolate* isolate, RegExpCompiler* compiler, + uc16 c, Label* on_failure, int cp_offset, + bool check, bool preloaded) { + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + bool one_byte = compiler->one_byte(); + unibrow::uchar chars[4]; + int length = GetCaseIndependentLetters(isolate, c, one_byte, chars, 4); + if (length <= 1) return false; + // We may not need to check against the end of the input string + // if this character lies before a character that matched. + if (!preloaded) { + macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check); + } + Label ok; + switch (length) { + case 2: { + if (ShortCutEmitCharacterPair(macro_assembler, one_byte, chars[0], + chars[1], on_failure)) { + } else { + macro_assembler->CheckCharacter(chars[0], &ok); + macro_assembler->CheckNotCharacter(chars[1], on_failure); + macro_assembler->Bind(&ok); + } + break; + } + case 4: + macro_assembler->CheckCharacter(chars[3], &ok); + V8_FALLTHROUGH; + case 3: + macro_assembler->CheckCharacter(chars[0], &ok); + macro_assembler->CheckCharacter(chars[1], &ok); + macro_assembler->CheckNotCharacter(chars[2], on_failure); + macro_assembler->Bind(&ok); + break; + default: + UNREACHABLE(); + } + return true; +} + +static void EmitBoundaryTest(RegExpMacroAssembler* masm, int border, + Label* fall_through, Label* above_or_equal, + Label* below) { + if (below != fall_through) { + masm->CheckCharacterLT(border, below); + if (above_or_equal != fall_through) masm->GoTo(above_or_equal); + } else { + masm->CheckCharacterGT(border - 1, above_or_equal); + } +} + +static void EmitDoubleBoundaryTest(RegExpMacroAssembler* masm, int first, + int last, Label* fall_through, + Label* in_range, Label* out_of_range) { + if (in_range == fall_through) { + if (first == last) { + masm->CheckNotCharacter(first, out_of_range); + } else { + masm->CheckCharacterNotInRange(first, last, out_of_range); + } + } else { + if (first == last) { + masm->CheckCharacter(first, in_range); + } else { + masm->CheckCharacterInRange(first, last, in_range); + } + if (out_of_range != fall_through) masm->GoTo(out_of_range); + } +} + +// even_label is for ranges[i] to ranges[i + 1] where i - start_index is even. +// odd_label is for ranges[i] to ranges[i + 1] where i - start_index is odd. +static void EmitUseLookupTable(RegExpMacroAssembler* masm, + ZoneList<int>* ranges, int start_index, + int end_index, int min_char, Label* fall_through, + Label* even_label, Label* odd_label) { + static const int kSize = RegExpMacroAssembler::kTableSize; + static const int kMask = RegExpMacroAssembler::kTableMask; + + int base = (min_char & ~kMask); + USE(base); + + // Assert that everything is on one kTableSize page. + for (int i = start_index; i <= end_index; i++) { + DCHECK_EQ(ranges->at(i) & ~kMask, base); + } + DCHECK(start_index == 0 || (ranges->at(start_index - 1) & ~kMask) <= base); + + char templ[kSize]; + Label* on_bit_set; + Label* on_bit_clear; + int bit; + if (even_label == fall_through) { + on_bit_set = odd_label; + on_bit_clear = even_label; + bit = 1; + } else { + on_bit_set = even_label; + on_bit_clear = odd_label; + bit = 0; + } + for (int i = 0; i < (ranges->at(start_index) & kMask) && i < kSize; i++) { + templ[i] = bit; + } + int j = 0; + bit ^= 1; + for (int i = start_index; i < end_index; i++) { + for (j = (ranges->at(i) & kMask); j < (ranges->at(i + 1) & kMask); j++) { + templ[j] = bit; + } + bit ^= 1; + } + for (int i = j; i < kSize; i++) { + templ[i] = bit; + } + Factory* factory = masm->isolate()->factory(); + // TODO(erikcorry): Cache these. + Handle<ByteArray> ba = factory->NewByteArray(kSize, AllocationType::kOld); + for (int i = 0; i < kSize; i++) { + ba->set(i, templ[i]); + } + masm->CheckBitInTable(ba, on_bit_set); + if (on_bit_clear != fall_through) masm->GoTo(on_bit_clear); +} + +static void CutOutRange(RegExpMacroAssembler* masm, ZoneList<int>* ranges, + int start_index, int end_index, int cut_index, + Label* even_label, Label* odd_label) { + bool odd = (((cut_index - start_index) & 1) == 1); + Label* in_range_label = odd ? odd_label : even_label; + Label dummy; + EmitDoubleBoundaryTest(masm, ranges->at(cut_index), + ranges->at(cut_index + 1) - 1, &dummy, in_range_label, + &dummy); + DCHECK(!dummy.is_linked()); + // Cut out the single range by rewriting the array. This creates a new + // range that is a merger of the two ranges on either side of the one we + // are cutting out. The oddity of the labels is preserved. + for (int j = cut_index; j > start_index; j--) { + ranges->at(j) = ranges->at(j - 1); + } + for (int j = cut_index + 1; j < end_index; j++) { + ranges->at(j) = ranges->at(j + 1); + } +} + +// Unicode case. Split the search space into kSize spaces that are handled +// with recursion. +static void SplitSearchSpace(ZoneList<int>* ranges, int start_index, + int end_index, int* new_start_index, + int* new_end_index, int* border) { + static const int kSize = RegExpMacroAssembler::kTableSize; + static const int kMask = RegExpMacroAssembler::kTableMask; + + int first = ranges->at(start_index); + int last = ranges->at(end_index) - 1; + + *new_start_index = start_index; + *border = (ranges->at(start_index) & ~kMask) + kSize; + while (*new_start_index < end_index) { + if (ranges->at(*new_start_index) > *border) break; + (*new_start_index)++; + } + // new_start_index is the index of the first edge that is beyond the + // current kSize space. + + // For very large search spaces we do a binary chop search of the non-Latin1 + // space instead of just going to the end of the current kSize space. The + // heuristics are complicated a little by the fact that any 128-character + // encoding space can be quickly tested with a table lookup, so we don't + // wish to do binary chop search at a smaller granularity than that. A + // 128-character space can take up a lot of space in the ranges array if, + // for example, we only want to match every second character (eg. the lower + // case characters on some Unicode pages). + int binary_chop_index = (end_index + start_index) / 2; + // The first test ensures that we get to the code that handles the Latin1 + // range with a single not-taken branch, speeding up this important + // character range (even non-Latin1 charset-based text has spaces and + // punctuation). + if (*border - 1 > String::kMaxOneByteCharCode && // Latin1 case. + end_index - start_index > (*new_start_index - start_index) * 2 && + last - first > kSize * 2 && binary_chop_index > *new_start_index && + ranges->at(binary_chop_index) >= first + 2 * kSize) { + int scan_forward_for_section_border = binary_chop_index; + int new_border = (ranges->at(binary_chop_index) | kMask) + 1; + + while (scan_forward_for_section_border < end_index) { + if (ranges->at(scan_forward_for_section_border) > new_border) { + *new_start_index = scan_forward_for_section_border; + *border = new_border; + break; + } + scan_forward_for_section_border++; + } + } + + DCHECK(*new_start_index > start_index); + *new_end_index = *new_start_index - 1; + if (ranges->at(*new_end_index) == *border) { + (*new_end_index)--; + } + if (*border >= ranges->at(end_index)) { + *border = ranges->at(end_index); + *new_start_index = end_index; // Won't be used. + *new_end_index = end_index - 1; + } +} + +// Gets a series of segment boundaries representing a character class. If the +// character is in the range between an even and an odd boundary (counting from +// start_index) then go to even_label, otherwise go to odd_label. We already +// know that the character is in the range of min_char to max_char inclusive. +// Either label can be nullptr indicating backtracking. Either label can also +// be equal to the fall_through label. +static void GenerateBranches(RegExpMacroAssembler* masm, ZoneList<int>* ranges, + int start_index, int end_index, uc32 min_char, + uc32 max_char, Label* fall_through, + Label* even_label, Label* odd_label) { + DCHECK_LE(min_char, String::kMaxUtf16CodeUnit); + DCHECK_LE(max_char, String::kMaxUtf16CodeUnit); + + int first = ranges->at(start_index); + int last = ranges->at(end_index) - 1; + + DCHECK_LT(min_char, first); + + // Just need to test if the character is before or on-or-after + // a particular character. + if (start_index == end_index) { + EmitBoundaryTest(masm, first, fall_through, even_label, odd_label); + return; + } + + // Another almost trivial case: There is one interval in the middle that is + // different from the end intervals. + if (start_index + 1 == end_index) { + EmitDoubleBoundaryTest(masm, first, last, fall_through, even_label, + odd_label); + return; + } + + // It's not worth using table lookup if there are very few intervals in the + // character class. + if (end_index - start_index <= 6) { + // It is faster to test for individual characters, so we look for those + // first, then try arbitrary ranges in the second round. + static int kNoCutIndex = -1; + int cut = kNoCutIndex; + for (int i = start_index; i < end_index; i++) { + if (ranges->at(i) == ranges->at(i + 1) - 1) { + cut = i; + break; + } + } + if (cut == kNoCutIndex) cut = start_index; + CutOutRange(masm, ranges, start_index, end_index, cut, even_label, + odd_label); + DCHECK_GE(end_index - start_index, 2); + GenerateBranches(masm, ranges, start_index + 1, end_index - 1, min_char, + max_char, fall_through, even_label, odd_label); + return; + } + + // If there are a lot of intervals in the regexp, then we will use tables to + // determine whether the character is inside or outside the character class. + static const int kBits = RegExpMacroAssembler::kTableSizeBits; + + if ((max_char >> kBits) == (min_char >> kBits)) { + EmitUseLookupTable(masm, ranges, start_index, end_index, min_char, + fall_through, even_label, odd_label); + return; + } + + if ((min_char >> kBits) != (first >> kBits)) { + masm->CheckCharacterLT(first, odd_label); + GenerateBranches(masm, ranges, start_index + 1, end_index, first, max_char, + fall_through, odd_label, even_label); + return; + } + + int new_start_index = 0; + int new_end_index = 0; + int border = 0; + + SplitSearchSpace(ranges, start_index, end_index, &new_start_index, + &new_end_index, &border); + + Label handle_rest; + Label* above = &handle_rest; + if (border == last + 1) { + // We didn't find any section that started after the limit, so everything + // above the border is one of the terminal labels. + above = (end_index & 1) != (start_index & 1) ? odd_label : even_label; + DCHECK(new_end_index == end_index - 1); + } + + DCHECK_LE(start_index, new_end_index); + DCHECK_LE(new_start_index, end_index); + DCHECK_LT(start_index, new_start_index); + DCHECK_LT(new_end_index, end_index); + DCHECK(new_end_index + 1 == new_start_index || + (new_end_index + 2 == new_start_index && + border == ranges->at(new_end_index + 1))); + DCHECK_LT(min_char, border - 1); + DCHECK_LT(border, max_char); + DCHECK_LT(ranges->at(new_end_index), border); + DCHECK(border < ranges->at(new_start_index) || + (border == ranges->at(new_start_index) && + new_start_index == end_index && new_end_index == end_index - 1 && + border == last + 1)); + DCHECK(new_start_index == 0 || border >= ranges->at(new_start_index - 1)); + + masm->CheckCharacterGT(border - 1, above); + Label dummy; + GenerateBranches(masm, ranges, start_index, new_end_index, min_char, + border - 1, &dummy, even_label, odd_label); + if (handle_rest.is_linked()) { + masm->Bind(&handle_rest); + bool flip = (new_start_index & 1) != (start_index & 1); + GenerateBranches(masm, ranges, new_start_index, end_index, border, max_char, + &dummy, flip ? odd_label : even_label, + flip ? even_label : odd_label); + } +} + +static void EmitCharClass(RegExpMacroAssembler* macro_assembler, + RegExpCharacterClass* cc, bool one_byte, + Label* on_failure, int cp_offset, bool check_offset, + bool preloaded, Zone* zone) { + ZoneList<CharacterRange>* ranges = cc->ranges(zone); + CharacterRange::Canonicalize(ranges); + + int max_char; + if (one_byte) { + max_char = String::kMaxOneByteCharCode; + } else { + max_char = String::kMaxUtf16CodeUnit; + } + + int range_count = ranges->length(); + + int last_valid_range = range_count - 1; + while (last_valid_range >= 0) { + CharacterRange& range = ranges->at(last_valid_range); + if (range.from() <= max_char) { + break; + } + last_valid_range--; + } + + if (last_valid_range < 0) { + if (!cc->is_negated()) { + macro_assembler->GoTo(on_failure); + } + if (check_offset) { + macro_assembler->CheckPosition(cp_offset, on_failure); + } + return; + } + + if (last_valid_range == 0 && ranges->at(0).IsEverything(max_char)) { + if (cc->is_negated()) { + macro_assembler->GoTo(on_failure); + } else { + // This is a common case hit by non-anchored expressions. + if (check_offset) { + macro_assembler->CheckPosition(cp_offset, on_failure); + } + } + return; + } + + if (!preloaded) { + macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check_offset); + } + + if (cc->is_standard(zone) && macro_assembler->CheckSpecialCharacterClass( + cc->standard_type(), on_failure)) { + return; + } + + // A new list with ascending entries. Each entry is a code unit + // where there is a boundary between code units that are part of + // the class and code units that are not. Normally we insert an + // entry at zero which goes to the failure label, but if there + // was already one there we fall through for success on that entry. + // Subsequent entries have alternating meaning (success/failure). + ZoneList<int>* range_boundaries = + new (zone) ZoneList<int>(last_valid_range, zone); + + bool zeroth_entry_is_failure = !cc->is_negated(); + + for (int i = 0; i <= last_valid_range; i++) { + CharacterRange& range = ranges->at(i); + if (range.from() == 0) { + DCHECK_EQ(i, 0); + zeroth_entry_is_failure = !zeroth_entry_is_failure; + } else { + range_boundaries->Add(range.from(), zone); + } + range_boundaries->Add(range.to() + 1, zone); + } + int end_index = range_boundaries->length() - 1; + if (range_boundaries->at(end_index) > max_char) { + end_index--; + } + + Label fall_through; + GenerateBranches(macro_assembler, range_boundaries, + 0, // start_index. + end_index, + 0, // min_char. + max_char, &fall_through, + zeroth_entry_is_failure ? &fall_through : on_failure, + zeroth_entry_is_failure ? on_failure : &fall_through); + macro_assembler->Bind(&fall_through); +} + +RegExpNode::~RegExpNode() = default; + +RegExpNode::LimitResult RegExpNode::LimitVersions(RegExpCompiler* compiler, + Trace* trace) { + // If we are generating a greedy loop then don't stop and don't reuse code. + if (trace->stop_node() != nullptr) { + return CONTINUE; + } + + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + if (trace->is_trivial()) { + if (label_.is_bound() || on_work_list() || !KeepRecursing(compiler)) { + // If a generic version is already scheduled to be generated or we have + // recursed too deeply then just generate a jump to that code. + macro_assembler->GoTo(&label_); + // This will queue it up for generation of a generic version if it hasn't + // already been queued. + compiler->AddWork(this); + return DONE; + } + // Generate generic version of the node and bind the label for later use. + macro_assembler->Bind(&label_); + return CONTINUE; + } + + // We are being asked to make a non-generic version. Keep track of how many + // non-generic versions we generate so as not to overdo it. + trace_count_++; + if (KeepRecursing(compiler) && compiler->optimize() && + trace_count_ < kMaxCopiesCodeGenerated) { + return CONTINUE; + } + + // If we get here code has been generated for this node too many times or + // recursion is too deep. Time to switch to a generic version. The code for + // generic versions above can handle deep recursion properly. + bool was_limiting = compiler->limiting_recursion(); + compiler->set_limiting_recursion(true); + trace->Flush(compiler, this); + compiler->set_limiting_recursion(was_limiting); + return DONE; +} + +bool RegExpNode::KeepRecursing(RegExpCompiler* compiler) { + return !compiler->limiting_recursion() && + compiler->recursion_depth() <= RegExpCompiler::kMaxRecursion; +} + +void ActionNode::FillInBMInfo(Isolate* isolate, int offset, int budget, + BoyerMooreLookahead* bm, bool not_at_start) { + if (action_type_ == POSITIVE_SUBMATCH_SUCCESS) { + // Anything may follow a positive submatch success, thus we need to accept + // all characters from this position onwards. + bm->SetRest(offset); + } else { + on_success()->FillInBMInfo(isolate, offset, budget - 1, bm, not_at_start); + } + SaveBMInfo(bm, not_at_start, offset); +} + +void ActionNode::GetQuickCheckDetails(QuickCheckDetails* details, + RegExpCompiler* compiler, int filled_in, + bool not_at_start) { + if (action_type_ == SET_REGISTER_FOR_LOOP) { + on_success()->GetQuickCheckDetailsFromLoopEntry(details, compiler, + filled_in, not_at_start); + } else { + on_success()->GetQuickCheckDetails(details, compiler, filled_in, + not_at_start); + } +} + +void AssertionNode::FillInBMInfo(Isolate* isolate, int offset, int budget, + BoyerMooreLookahead* bm, bool not_at_start) { + // Match the behaviour of EatsAtLeast on this node. + if (assertion_type() == AT_START && not_at_start) return; + on_success()->FillInBMInfo(isolate, offset, budget - 1, bm, not_at_start); + SaveBMInfo(bm, not_at_start, offset); +} + +void NegativeLookaroundChoiceNode::GetQuickCheckDetails( + QuickCheckDetails* details, RegExpCompiler* compiler, int filled_in, + bool not_at_start) { + RegExpNode* node = continue_node(); + return node->GetQuickCheckDetails(details, compiler, filled_in, not_at_start); +} + +// Takes the left-most 1-bit and smears it out, setting all bits to its right. +static inline uint32_t SmearBitsRight(uint32_t v) { + v |= v >> 1; + v |= v >> 2; + v |= v >> 4; + v |= v >> 8; + v |= v >> 16; + return v; +} + +bool QuickCheckDetails::Rationalize(bool asc) { + bool found_useful_op = false; + uint32_t char_mask; + if (asc) { + char_mask = String::kMaxOneByteCharCode; + } else { + char_mask = String::kMaxUtf16CodeUnit; + } + mask_ = 0; + value_ = 0; + int char_shift = 0; + for (int i = 0; i < characters_; i++) { + Position* pos = &positions_[i]; + if ((pos->mask & String::kMaxOneByteCharCode) != 0) { + found_useful_op = true; + } + mask_ |= (pos->mask & char_mask) << char_shift; + value_ |= (pos->value & char_mask) << char_shift; + char_shift += asc ? 8 : 16; + } + return found_useful_op; +} + +int RegExpNode::EatsAtLeast(bool not_at_start) { + return not_at_start ? eats_at_least_.eats_at_least_from_not_start + : eats_at_least_.eats_at_least_from_possibly_start; +} + +EatsAtLeastInfo RegExpNode::EatsAtLeastFromLoopEntry() { + // SET_REGISTER_FOR_LOOP is only used to initialize loop counters, and it + // implies that the following node must be a LoopChoiceNode. If we need to + // set registers to constant values for other reasons, we could introduce a + // new action type SET_REGISTER that doesn't imply anything about its + // successor. + UNREACHABLE(); +} + +void RegExpNode::GetQuickCheckDetailsFromLoopEntry(QuickCheckDetails* details, + RegExpCompiler* compiler, + int characters_filled_in, + bool not_at_start) { + // See comment in RegExpNode::EatsAtLeastFromLoopEntry. + UNREACHABLE(); +} + +EatsAtLeastInfo LoopChoiceNode::EatsAtLeastFromLoopEntry() { + DCHECK_EQ(alternatives_->length(), 2); // There's just loop and continue. + + if (read_backward()) { + // Can't do anything special for a backward loop, so return the basic values + // that we got during analysis. + return *eats_at_least_info(); + } + + // Figure out how much the loop body itself eats, not including anything in + // the continuation case. In general, the nodes in the loop body should report + // that they eat at least the number eaten by the continuation node, since any + // successful match in the loop body must also include the continuation node. + // However, in some cases involving positive lookaround, the loop body under- + // reports its appetite, so use saturated math here to avoid negative numbers. + uint8_t loop_body_from_not_start = base::saturated_cast<uint8_t>( + loop_node_->EatsAtLeast(true) - continue_node_->EatsAtLeast(true)); + uint8_t loop_body_from_possibly_start = base::saturated_cast<uint8_t>( + loop_node_->EatsAtLeast(false) - continue_node_->EatsAtLeast(true)); + + // Limit the number of loop iterations to avoid overflow in subsequent steps. + int loop_iterations = base::saturated_cast<uint8_t>(min_loop_iterations()); + + EatsAtLeastInfo result; + result.eats_at_least_from_not_start = + base::saturated_cast<uint8_t>(loop_iterations * loop_body_from_not_start + + continue_node_->EatsAtLeast(true)); + if (loop_iterations > 0 && loop_body_from_possibly_start > 0) { + // First loop iteration eats at least one, so all subsequent iterations + // and the after-loop chunk are guaranteed to not be at the start. + result.eats_at_least_from_possibly_start = base::saturated_cast<uint8_t>( + loop_body_from_possibly_start + + (loop_iterations - 1) * loop_body_from_not_start + + continue_node_->EatsAtLeast(true)); + } else { + // Loop body might eat nothing, so only continue node contributes. + result.eats_at_least_from_possibly_start = + continue_node_->EatsAtLeast(false); + } + return result; +} + +bool RegExpNode::EmitQuickCheck(RegExpCompiler* compiler, + Trace* bounds_check_trace, Trace* trace, + bool preload_has_checked_bounds, + Label* on_possible_success, + QuickCheckDetails* details, + bool fall_through_on_failure, + ChoiceNode* predecessor) { + DCHECK_NOT_NULL(predecessor); + if (details->characters() == 0) return false; + GetQuickCheckDetails(details, compiler, 0, + trace->at_start() == Trace::FALSE_VALUE); + if (details->cannot_match()) return false; + if (!details->Rationalize(compiler->one_byte())) return false; + DCHECK(details->characters() == 1 || + compiler->macro_assembler()->CanReadUnaligned()); + uint32_t mask = details->mask(); + uint32_t value = details->value(); + + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + + if (trace->characters_preloaded() != details->characters()) { + DCHECK(trace->cp_offset() == bounds_check_trace->cp_offset()); + // The bounds check is performed using the minimum number of characters + // any choice would eat, so if the bounds check fails, then none of the + // choices can succeed, so we can just immediately backtrack, rather + // than go to the next choice. The number of characters preloaded may be + // less than the number used for the bounds check. + int eats_at_least = predecessor->EatsAtLeast( + bounds_check_trace->at_start() == Trace::FALSE_VALUE); + DCHECK_GE(eats_at_least, details->characters()); + assembler->LoadCurrentCharacter( + trace->cp_offset(), bounds_check_trace->backtrack(), + !preload_has_checked_bounds, details->characters(), eats_at_least); + } + + bool need_mask = true; + + if (details->characters() == 1) { + // If number of characters preloaded is 1 then we used a byte or 16 bit + // load so the value is already masked down. + uint32_t char_mask; + if (compiler->one_byte()) { + char_mask = String::kMaxOneByteCharCode; + } else { + char_mask = String::kMaxUtf16CodeUnit; + } + if ((mask & char_mask) == char_mask) need_mask = false; + mask &= char_mask; + } else { + // For 2-character preloads in one-byte mode or 1-character preloads in + // two-byte mode we also use a 16 bit load with zero extend. + static const uint32_t kTwoByteMask = 0xFFFF; + static const uint32_t kFourByteMask = 0xFFFFFFFF; + if (details->characters() == 2 && compiler->one_byte()) { + if ((mask & kTwoByteMask) == kTwoByteMask) need_mask = false; + } else if (details->characters() == 1 && !compiler->one_byte()) { + if ((mask & kTwoByteMask) == kTwoByteMask) need_mask = false; + } else { + if (mask == kFourByteMask) need_mask = false; + } + } + + if (fall_through_on_failure) { + if (need_mask) { + assembler->CheckCharacterAfterAnd(value, mask, on_possible_success); + } else { + assembler->CheckCharacter(value, on_possible_success); + } + } else { + if (need_mask) { + assembler->CheckNotCharacterAfterAnd(value, mask, trace->backtrack()); + } else { + assembler->CheckNotCharacter(value, trace->backtrack()); + } + } + return true; +} + +// Here is the meat of GetQuickCheckDetails (see also the comment on the +// super-class in the .h file). +// +// We iterate along the text object, building up for each character a +// mask and value that can be used to test for a quick failure to match. +// The masks and values for the positions will be combined into a single +// machine word for the current character width in order to be used in +// generating a quick check. +void TextNode::GetQuickCheckDetails(QuickCheckDetails* details, + RegExpCompiler* compiler, + int characters_filled_in, + bool not_at_start) { + // Do not collect any quick check details if the text node reads backward, + // since it reads in the opposite direction than we use for quick checks. + if (read_backward()) return; + Isolate* isolate = compiler->macro_assembler()->isolate(); + DCHECK(characters_filled_in < details->characters()); + int characters = details->characters(); + int char_mask; + if (compiler->one_byte()) { + char_mask = String::kMaxOneByteCharCode; + } else { + char_mask = String::kMaxUtf16CodeUnit; + } + for (int k = 0; k < elements()->length(); k++) { + TextElement elm = elements()->at(k); + if (elm.text_type() == TextElement::ATOM) { + Vector<const uc16> quarks = elm.atom()->data(); + for (int i = 0; i < characters && i < quarks.length(); i++) { + QuickCheckDetails::Position* pos = + details->positions(characters_filled_in); + uc16 c = quarks[i]; + if (elm.atom()->ignore_case()) { + unibrow::uchar chars[4]; + int length = GetCaseIndependentLetters( + isolate, c, compiler->one_byte(), chars, 4); + if (length == 0) { + // This can happen because all case variants are non-Latin1, but we + // know the input is Latin1. + details->set_cannot_match(); + pos->determines_perfectly = false; + return; + } + if (length == 1) { + // This letter has no case equivalents, so it's nice and simple + // and the mask-compare will determine definitely whether we have + // a match at this character position. + pos->mask = char_mask; + pos->value = chars[0]; + pos->determines_perfectly = true; + } else { + uint32_t common_bits = char_mask; + uint32_t bits = chars[0]; + for (int j = 1; j < length; j++) { + uint32_t differing_bits = ((chars[j] & common_bits) ^ bits); + common_bits ^= differing_bits; + bits &= common_bits; + } + // If length is 2 and common bits has only one zero in it then + // our mask and compare instruction will determine definitely + // whether we have a match at this character position. Otherwise + // it can only be an approximate check. + uint32_t one_zero = (common_bits | ~char_mask); + if (length == 2 && ((~one_zero) & ((~one_zero) - 1)) == 0) { + pos->determines_perfectly = true; + } + pos->mask = common_bits; + pos->value = bits; + } + } else { + // Don't ignore case. Nice simple case where the mask-compare will + // determine definitely whether we have a match at this character + // position. + if (c > char_mask) { + details->set_cannot_match(); + pos->determines_perfectly = false; + return; + } + pos->mask = char_mask; + pos->value = c; + pos->determines_perfectly = true; + } + characters_filled_in++; + DCHECK(characters_filled_in <= details->characters()); + if (characters_filled_in == details->characters()) { + return; + } + } + } else { + QuickCheckDetails::Position* pos = + details->positions(characters_filled_in); + RegExpCharacterClass* tree = elm.char_class(); + ZoneList<CharacterRange>* ranges = tree->ranges(zone()); + DCHECK(!ranges->is_empty()); + if (tree->is_negated()) { + // A quick check uses multi-character mask and compare. There is no + // useful way to incorporate a negative char class into this scheme + // so we just conservatively create a mask and value that will always + // succeed. + pos->mask = 0; + pos->value = 0; + } else { + int first_range = 0; + while (ranges->at(first_range).from() > char_mask) { + first_range++; + if (first_range == ranges->length()) { + details->set_cannot_match(); + pos->determines_perfectly = false; + return; + } + } + CharacterRange range = ranges->at(first_range); + uc16 from = range.from(); + uc16 to = range.to(); + if (to > char_mask) { + to = char_mask; + } + uint32_t differing_bits = (from ^ to); + // A mask and compare is only perfect if the differing bits form a + // number like 00011111 with one single block of trailing 1s. + if ((differing_bits & (differing_bits + 1)) == 0 && + from + differing_bits == to) { + pos->determines_perfectly = true; + } + uint32_t common_bits = ~SmearBitsRight(differing_bits); + uint32_t bits = (from & common_bits); + for (int i = first_range + 1; i < ranges->length(); i++) { + CharacterRange range = ranges->at(i); + uc16 from = range.from(); + uc16 to = range.to(); + if (from > char_mask) continue; + if (to > char_mask) to = char_mask; + // Here we are combining more ranges into the mask and compare + // value. With each new range the mask becomes more sparse and + // so the chances of a false positive rise. A character class + // with multiple ranges is assumed never to be equivalent to a + // mask and compare operation. + pos->determines_perfectly = false; + uint32_t new_common_bits = (from ^ to); + new_common_bits = ~SmearBitsRight(new_common_bits); + common_bits &= new_common_bits; + bits &= new_common_bits; + uint32_t differing_bits = (from & common_bits) ^ bits; + common_bits ^= differing_bits; + bits &= common_bits; + } + pos->mask = common_bits; + pos->value = bits; + } + characters_filled_in++; + DCHECK(characters_filled_in <= details->characters()); + if (characters_filled_in == details->characters()) { + return; + } + } + } + DCHECK(characters_filled_in != details->characters()); + if (!details->cannot_match()) { + on_success()->GetQuickCheckDetails(details, compiler, characters_filled_in, + true); + } +} + +void QuickCheckDetails::Clear() { + for (int i = 0; i < characters_; i++) { + positions_[i].mask = 0; + positions_[i].value = 0; + positions_[i].determines_perfectly = false; + } + characters_ = 0; +} + +void QuickCheckDetails::Advance(int by, bool one_byte) { + if (by >= characters_ || by < 0) { + DCHECK_IMPLIES(by < 0, characters_ == 0); + Clear(); + return; + } + DCHECK_LE(characters_ - by, 4); + DCHECK_LE(characters_, 4); + for (int i = 0; i < characters_ - by; i++) { + positions_[i] = positions_[by + i]; + } + for (int i = characters_ - by; i < characters_; i++) { + positions_[i].mask = 0; + positions_[i].value = 0; + positions_[i].determines_perfectly = false; + } + characters_ -= by; + // We could change mask_ and value_ here but we would never advance unless + // they had already been used in a check and they won't be used again because + // it would gain us nothing. So there's no point. +} + +void QuickCheckDetails::Merge(QuickCheckDetails* other, int from_index) { + DCHECK(characters_ == other->characters_); + if (other->cannot_match_) { + return; + } + if (cannot_match_) { + *this = *other; + return; + } + for (int i = from_index; i < characters_; i++) { + QuickCheckDetails::Position* pos = positions(i); + QuickCheckDetails::Position* other_pos = other->positions(i); + if (pos->mask != other_pos->mask || pos->value != other_pos->value || + !other_pos->determines_perfectly) { + // Our mask-compare operation will be approximate unless we have the + // exact same operation on both sides of the alternation. + pos->determines_perfectly = false; + } + pos->mask &= other_pos->mask; + pos->value &= pos->mask; + other_pos->value &= pos->mask; + uc16 differing_bits = (pos->value ^ other_pos->value); + pos->mask &= ~differing_bits; + pos->value &= pos->mask; + } +} + +class VisitMarker { + public: + explicit VisitMarker(NodeInfo* info) : info_(info) { + DCHECK(!info->visited); + info->visited = true; + } + ~VisitMarker() { info_->visited = false; } + + private: + NodeInfo* info_; +}; + +// Temporarily sets traversed_loop_initialization_node_. +class LoopInitializationMarker { + public: + explicit LoopInitializationMarker(LoopChoiceNode* node) : node_(node) { + DCHECK(!node_->traversed_loop_initialization_node_); + node_->traversed_loop_initialization_node_ = true; + } + ~LoopInitializationMarker() { + DCHECK(node_->traversed_loop_initialization_node_); + node_->traversed_loop_initialization_node_ = false; + } + + private: + LoopChoiceNode* node_; + DISALLOW_COPY_AND_ASSIGN(LoopInitializationMarker); +}; + +// Temporarily decrements min_loop_iterations_. +class IterationDecrementer { + public: + explicit IterationDecrementer(LoopChoiceNode* node) : node_(node) { + DCHECK_GT(node_->min_loop_iterations_, 0); + --node_->min_loop_iterations_; + } + ~IterationDecrementer() { ++node_->min_loop_iterations_; } + + private: + LoopChoiceNode* node_; + DISALLOW_COPY_AND_ASSIGN(IterationDecrementer); +}; + +RegExpNode* SeqRegExpNode::FilterOneByte(int depth) { + if (info()->replacement_calculated) return replacement(); + if (depth < 0) return this; + DCHECK(!info()->visited); + VisitMarker marker(info()); + return FilterSuccessor(depth - 1); +} + +RegExpNode* SeqRegExpNode::FilterSuccessor(int depth) { + RegExpNode* next = on_success_->FilterOneByte(depth - 1); + if (next == nullptr) return set_replacement(nullptr); + on_success_ = next; + return set_replacement(this); +} + +// We need to check for the following characters: 0x39C 0x3BC 0x178. +bool RangeContainsLatin1Equivalents(CharacterRange range) { + // TODO(dcarney): this could be a lot more efficient. + return range.Contains(0x039C) || range.Contains(0x03BC) || + range.Contains(0x0178); +} + +static bool RangesContainLatin1Equivalents(ZoneList<CharacterRange>* ranges) { + for (int i = 0; i < ranges->length(); i++) { + // TODO(dcarney): this could be a lot more efficient. + if (RangeContainsLatin1Equivalents(ranges->at(i))) return true; + } + return false; +} + +RegExpNode* TextNode::FilterOneByte(int depth) { + if (info()->replacement_calculated) return replacement(); + if (depth < 0) return this; + DCHECK(!info()->visited); + VisitMarker marker(info()); + int element_count = elements()->length(); + for (int i = 0; i < element_count; i++) { + TextElement elm = elements()->at(i); + if (elm.text_type() == TextElement::ATOM) { + Vector<const uc16> quarks = elm.atom()->data(); + for (int j = 0; j < quarks.length(); j++) { + uint16_t c = quarks[j]; + if (elm.atom()->ignore_case()) { + c = unibrow::Latin1::TryConvertToLatin1(c); + } + if (c > unibrow::Latin1::kMaxChar) return set_replacement(nullptr); + // Replace quark in case we converted to Latin-1. + uint16_t* writable_quarks = const_cast<uint16_t*>(quarks.begin()); + writable_quarks[j] = c; + } + } else { + DCHECK(elm.text_type() == TextElement::CHAR_CLASS); + RegExpCharacterClass* cc = elm.char_class(); + ZoneList<CharacterRange>* ranges = cc->ranges(zone()); + CharacterRange::Canonicalize(ranges); + // Now they are in order so we only need to look at the first. + int range_count = ranges->length(); + if (cc->is_negated()) { + if (range_count != 0 && ranges->at(0).from() == 0 && + ranges->at(0).to() >= String::kMaxOneByteCharCode) { + // This will be handled in a later filter. + if (IgnoreCase(cc->flags()) && RangesContainLatin1Equivalents(ranges)) + continue; + return set_replacement(nullptr); + } + } else { + if (range_count == 0 || + ranges->at(0).from() > String::kMaxOneByteCharCode) { + // This will be handled in a later filter. + if (IgnoreCase(cc->flags()) && RangesContainLatin1Equivalents(ranges)) + continue; + return set_replacement(nullptr); + } + } + } + } + return FilterSuccessor(depth - 1); +} + +RegExpNode* LoopChoiceNode::FilterOneByte(int depth) { + if (info()->replacement_calculated) return replacement(); + if (depth < 0) return this; + if (info()->visited) return this; + { + VisitMarker marker(info()); + + RegExpNode* continue_replacement = continue_node_->FilterOneByte(depth - 1); + // If we can't continue after the loop then there is no sense in doing the + // loop. + if (continue_replacement == nullptr) return set_replacement(nullptr); + } + + return ChoiceNode::FilterOneByte(depth - 1); +} + +RegExpNode* ChoiceNode::FilterOneByte(int depth) { + if (info()->replacement_calculated) return replacement(); + if (depth < 0) return this; + if (info()->visited) return this; + VisitMarker marker(info()); + int choice_count = alternatives_->length(); + + for (int i = 0; i < choice_count; i++) { + GuardedAlternative alternative = alternatives_->at(i); + if (alternative.guards() != nullptr && + alternative.guards()->length() != 0) { + set_replacement(this); + return this; + } + } + + int surviving = 0; + RegExpNode* survivor = nullptr; + for (int i = 0; i < choice_count; i++) { + GuardedAlternative alternative = alternatives_->at(i); + RegExpNode* replacement = alternative.node()->FilterOneByte(depth - 1); + DCHECK(replacement != this); // No missing EMPTY_MATCH_CHECK. + if (replacement != nullptr) { + alternatives_->at(i).set_node(replacement); + surviving++; + survivor = replacement; + } + } + if (surviving < 2) return set_replacement(survivor); + + set_replacement(this); + if (surviving == choice_count) { + return this; + } + // Only some of the nodes survived the filtering. We need to rebuild the + // alternatives list. + ZoneList<GuardedAlternative>* new_alternatives = + new (zone()) ZoneList<GuardedAlternative>(surviving, zone()); + for (int i = 0; i < choice_count; i++) { + RegExpNode* replacement = + alternatives_->at(i).node()->FilterOneByte(depth - 1); + if (replacement != nullptr) { + alternatives_->at(i).set_node(replacement); + new_alternatives->Add(alternatives_->at(i), zone()); + } + } + alternatives_ = new_alternatives; + return this; +} + +RegExpNode* NegativeLookaroundChoiceNode::FilterOneByte(int depth) { + if (info()->replacement_calculated) return replacement(); + if (depth < 0) return this; + if (info()->visited) return this; + VisitMarker marker(info()); + // Alternative 0 is the negative lookahead, alternative 1 is what comes + // afterwards. + RegExpNode* node = continue_node(); + RegExpNode* replacement = node->FilterOneByte(depth - 1); + if (replacement == nullptr) return set_replacement(nullptr); + alternatives_->at(kContinueIndex).set_node(replacement); + + RegExpNode* neg_node = lookaround_node(); + RegExpNode* neg_replacement = neg_node->FilterOneByte(depth - 1); + // If the negative lookahead is always going to fail then + // we don't need to check it. + if (neg_replacement == nullptr) return set_replacement(replacement); + alternatives_->at(kLookaroundIndex).set_node(neg_replacement); + return set_replacement(this); +} + +void LoopChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details, + RegExpCompiler* compiler, + int characters_filled_in, + bool not_at_start) { + if (body_can_be_zero_length_ || info()->visited) return; + not_at_start = not_at_start || this->not_at_start(); + DCHECK_EQ(alternatives_->length(), 2); // There's just loop and continue. + if (traversed_loop_initialization_node_ && min_loop_iterations_ > 0 && + loop_node_->EatsAtLeast(not_at_start) > + continue_node_->EatsAtLeast(true)) { + // Loop body is guaranteed to execute at least once, and consume characters + // when it does, meaning the only possible quick checks from this point + // begin with the loop body. We may recursively visit this LoopChoiceNode, + // but we temporarily decrease its minimum iteration counter so we know when + // to check the continue case. + IterationDecrementer next_iteration(this); + loop_node_->GetQuickCheckDetails(details, compiler, characters_filled_in, + not_at_start); + } else { + // Might not consume anything in the loop body, so treat it like a normal + // ChoiceNode (and don't recursively visit this node again). + VisitMarker marker(info()); + ChoiceNode::GetQuickCheckDetails(details, compiler, characters_filled_in, + not_at_start); + } +} + +void LoopChoiceNode::GetQuickCheckDetailsFromLoopEntry( + QuickCheckDetails* details, RegExpCompiler* compiler, + int characters_filled_in, bool not_at_start) { + if (traversed_loop_initialization_node_) { + // We already entered this loop once, exited via its continuation node, and + // followed an outer loop's back-edge to before the loop entry point. We + // could try to reset the minimum iteration count to its starting value at + // this point, but that seems like more trouble than it's worth. It's safe + // to keep going with the current (possibly reduced) minimum iteration + // count. + GetQuickCheckDetails(details, compiler, characters_filled_in, not_at_start); + } else { + // We are entering a loop via its counter initialization action, meaning we + // are guaranteed to run the loop body at least some minimum number of times + // before running the continuation node. Set a flag so that this node knows + // (now and any times we visit it again recursively) that it was entered + // from the top. + LoopInitializationMarker marker(this); + GetQuickCheckDetails(details, compiler, characters_filled_in, not_at_start); + } +} + +void LoopChoiceNode::FillInBMInfo(Isolate* isolate, int offset, int budget, + BoyerMooreLookahead* bm, bool not_at_start) { + if (body_can_be_zero_length_ || budget <= 0) { + bm->SetRest(offset); + SaveBMInfo(bm, not_at_start, offset); + return; + } + ChoiceNode::FillInBMInfo(isolate, offset, budget - 1, bm, not_at_start); + SaveBMInfo(bm, not_at_start, offset); +} + +void ChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details, + RegExpCompiler* compiler, + int characters_filled_in, + bool not_at_start) { + not_at_start = (not_at_start || not_at_start_); + int choice_count = alternatives_->length(); + DCHECK_LT(0, choice_count); + alternatives_->at(0).node()->GetQuickCheckDetails( + details, compiler, characters_filled_in, not_at_start); + for (int i = 1; i < choice_count; i++) { + QuickCheckDetails new_details(details->characters()); + RegExpNode* node = alternatives_->at(i).node(); + node->GetQuickCheckDetails(&new_details, compiler, characters_filled_in, + not_at_start); + // Here we merge the quick match details of the two branches. + details->Merge(&new_details, characters_filled_in); + } +} + +namespace { + +// Check for [0-9A-Z_a-z]. +void EmitWordCheck(RegExpMacroAssembler* assembler, Label* word, + Label* non_word, bool fall_through_on_word) { + if (assembler->CheckSpecialCharacterClass( + fall_through_on_word ? 'w' : 'W', + fall_through_on_word ? non_word : word)) { + // Optimized implementation available. + return; + } + assembler->CheckCharacterGT('z', non_word); + assembler->CheckCharacterLT('0', non_word); + assembler->CheckCharacterGT('a' - 1, word); + assembler->CheckCharacterLT('9' + 1, word); + assembler->CheckCharacterLT('A', non_word); + assembler->CheckCharacterLT('Z' + 1, word); + if (fall_through_on_word) { + assembler->CheckNotCharacter('_', non_word); + } else { + assembler->CheckCharacter('_', word); + } +} + +// Emit the code to check for a ^ in multiline mode (1-character lookbehind +// that matches newline or the start of input). +void EmitHat(RegExpCompiler* compiler, RegExpNode* on_success, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + + // We will load the previous character into the current character register. + Trace new_trace(*trace); + new_trace.InvalidateCurrentCharacter(); + + // A positive (> 0) cp_offset means we've already successfully matched a + // non-empty-width part of the pattern, and thus cannot be at or before the + // start of the subject string. We can thus skip both at-start and + // bounds-checks when loading the one-character lookbehind. + const bool may_be_at_or_before_subject_string_start = + new_trace.cp_offset() <= 0; + + Label ok; + if (may_be_at_or_before_subject_string_start) { + // The start of input counts as a newline in this context, so skip to ok if + // we are at the start. + assembler->CheckAtStart(new_trace.cp_offset(), &ok); + } + + // If we've already checked that we are not at the start of input, it's okay + // to load the previous character without bounds checks. + const bool can_skip_bounds_check = !may_be_at_or_before_subject_string_start; + assembler->LoadCurrentCharacter(new_trace.cp_offset() - 1, + new_trace.backtrack(), can_skip_bounds_check); + if (!assembler->CheckSpecialCharacterClass('n', new_trace.backtrack())) { + // Newline means \n, \r, 0x2028 or 0x2029. + if (!compiler->one_byte()) { + assembler->CheckCharacterAfterAnd(0x2028, 0xFFFE, &ok); + } + assembler->CheckCharacter('\n', &ok); + assembler->CheckNotCharacter('\r', new_trace.backtrack()); + } + assembler->Bind(&ok); + on_success->Emit(compiler, &new_trace); +} + +} // namespace + +// Emit the code to handle \b and \B (word-boundary or non-word-boundary). +void AssertionNode::EmitBoundaryCheck(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + Isolate* isolate = assembler->isolate(); + Trace::TriBool next_is_word_character = Trace::UNKNOWN; + bool not_at_start = (trace->at_start() == Trace::FALSE_VALUE); + BoyerMooreLookahead* lookahead = bm_info(not_at_start); + if (lookahead == nullptr) { + int eats_at_least = + Min(kMaxLookaheadForBoyerMoore, EatsAtLeast(not_at_start)); + if (eats_at_least >= 1) { + BoyerMooreLookahead* bm = + new (zone()) BoyerMooreLookahead(eats_at_least, compiler, zone()); + FillInBMInfo(isolate, 0, kRecursionBudget, bm, not_at_start); + if (bm->at(0)->is_non_word()) next_is_word_character = Trace::FALSE_VALUE; + if (bm->at(0)->is_word()) next_is_word_character = Trace::TRUE_VALUE; + } + } else { + if (lookahead->at(0)->is_non_word()) + next_is_word_character = Trace::FALSE_VALUE; + if (lookahead->at(0)->is_word()) next_is_word_character = Trace::TRUE_VALUE; + } + bool at_boundary = (assertion_type_ == AssertionNode::AT_BOUNDARY); + if (next_is_word_character == Trace::UNKNOWN) { + Label before_non_word; + Label before_word; + if (trace->characters_preloaded() != 1) { + assembler->LoadCurrentCharacter(trace->cp_offset(), &before_non_word); + } + // Fall through on non-word. + EmitWordCheck(assembler, &before_word, &before_non_word, false); + // Next character is not a word character. + assembler->Bind(&before_non_word); + Label ok; + BacktrackIfPrevious(compiler, trace, at_boundary ? kIsNonWord : kIsWord); + assembler->GoTo(&ok); + + assembler->Bind(&before_word); + BacktrackIfPrevious(compiler, trace, at_boundary ? kIsWord : kIsNonWord); + assembler->Bind(&ok); + } else if (next_is_word_character == Trace::TRUE_VALUE) { + BacktrackIfPrevious(compiler, trace, at_boundary ? kIsWord : kIsNonWord); + } else { + DCHECK(next_is_word_character == Trace::FALSE_VALUE); + BacktrackIfPrevious(compiler, trace, at_boundary ? kIsNonWord : kIsWord); + } +} + +void AssertionNode::BacktrackIfPrevious( + RegExpCompiler* compiler, Trace* trace, + AssertionNode::IfPrevious backtrack_if_previous) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + Trace new_trace(*trace); + new_trace.InvalidateCurrentCharacter(); + + Label fall_through; + Label* non_word = backtrack_if_previous == kIsNonWord ? new_trace.backtrack() + : &fall_through; + Label* word = backtrack_if_previous == kIsNonWord ? &fall_through + : new_trace.backtrack(); + + // A positive (> 0) cp_offset means we've already successfully matched a + // non-empty-width part of the pattern, and thus cannot be at or before the + // start of the subject string. We can thus skip both at-start and + // bounds-checks when loading the one-character lookbehind. + const bool may_be_at_or_before_subject_string_start = + new_trace.cp_offset() <= 0; + + if (may_be_at_or_before_subject_string_start) { + // The start of input counts as a non-word character, so the question is + // decided if we are at the start. + assembler->CheckAtStart(new_trace.cp_offset(), non_word); + } + + // If we've already checked that we are not at the start of input, it's okay + // to load the previous character without bounds checks. + const bool can_skip_bounds_check = !may_be_at_or_before_subject_string_start; + assembler->LoadCurrentCharacter(new_trace.cp_offset() - 1, non_word, + can_skip_bounds_check); + EmitWordCheck(assembler, word, non_word, backtrack_if_previous == kIsNonWord); + + assembler->Bind(&fall_through); + on_success()->Emit(compiler, &new_trace); +} + +void AssertionNode::GetQuickCheckDetails(QuickCheckDetails* details, + RegExpCompiler* compiler, + int filled_in, bool not_at_start) { + if (assertion_type_ == AT_START && not_at_start) { + details->set_cannot_match(); + return; + } + return on_success()->GetQuickCheckDetails(details, compiler, filled_in, + not_at_start); +} + +void AssertionNode::Emit(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + switch (assertion_type_) { + case AT_END: { + Label ok; + assembler->CheckPosition(trace->cp_offset(), &ok); + assembler->GoTo(trace->backtrack()); + assembler->Bind(&ok); + break; + } + case AT_START: { + if (trace->at_start() == Trace::FALSE_VALUE) { + assembler->GoTo(trace->backtrack()); + return; + } + if (trace->at_start() == Trace::UNKNOWN) { + assembler->CheckNotAtStart(trace->cp_offset(), trace->backtrack()); + Trace at_start_trace = *trace; + at_start_trace.set_at_start(Trace::TRUE_VALUE); + on_success()->Emit(compiler, &at_start_trace); + return; + } + } break; + case AFTER_NEWLINE: + EmitHat(compiler, on_success(), trace); + return; + case AT_BOUNDARY: + case AT_NON_BOUNDARY: { + EmitBoundaryCheck(compiler, trace); + return; + } + } + on_success()->Emit(compiler, trace); +} + +static bool DeterminedAlready(QuickCheckDetails* quick_check, int offset) { + if (quick_check == nullptr) return false; + if (offset >= quick_check->characters()) return false; + return quick_check->positions(offset)->determines_perfectly; +} + +static void UpdateBoundsCheck(int index, int* checked_up_to) { + if (index > *checked_up_to) { + *checked_up_to = index; + } +} + +// We call this repeatedly to generate code for each pass over the text node. +// The passes are in increasing order of difficulty because we hope one +// of the first passes will fail in which case we are saved the work of the +// later passes. for example for the case independent regexp /%[asdfghjkl]a/ +// we will check the '%' in the first pass, the case independent 'a' in the +// second pass and the character class in the last pass. +// +// The passes are done from right to left, so for example to test for /bar/ +// we will first test for an 'r' with offset 2, then an 'a' with offset 1 +// and then a 'b' with offset 0. This means we can avoid the end-of-input +// bounds check most of the time. In the example we only need to check for +// end-of-input when loading the putative 'r'. +// +// A slight complication involves the fact that the first character may already +// be fetched into a register by the previous node. In this case we want to +// do the test for that character first. We do this in separate passes. The +// 'preloaded' argument indicates that we are doing such a 'pass'. If such a +// pass has been performed then subsequent passes will have true in +// first_element_checked to indicate that that character does not need to be +// checked again. +// +// In addition to all this we are passed a Trace, which can +// contain an AlternativeGeneration object. In this AlternativeGeneration +// object we can see details of any quick check that was already passed in +// order to get to the code we are now generating. The quick check can involve +// loading characters, which means we do not need to recheck the bounds +// up to the limit the quick check already checked. In addition the quick +// check can have involved a mask and compare operation which may simplify +// or obviate the need for further checks at some character positions. +void TextNode::TextEmitPass(RegExpCompiler* compiler, TextEmitPassType pass, + bool preloaded, Trace* trace, + bool first_element_checked, int* checked_up_to) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + Isolate* isolate = assembler->isolate(); + bool one_byte = compiler->one_byte(); + Label* backtrack = trace->backtrack(); + QuickCheckDetails* quick_check = trace->quick_check_performed(); + int element_count = elements()->length(); + int backward_offset = read_backward() ? -Length() : 0; + for (int i = preloaded ? 0 : element_count - 1; i >= 0; i--) { + TextElement elm = elements()->at(i); + int cp_offset = trace->cp_offset() + elm.cp_offset() + backward_offset; + if (elm.text_type() == TextElement::ATOM) { + if (SkipPass(pass, elm.atom()->ignore_case())) continue; + Vector<const uc16> quarks = elm.atom()->data(); + for (int j = preloaded ? 0 : quarks.length() - 1; j >= 0; j--) { + if (first_element_checked && i == 0 && j == 0) continue; + if (DeterminedAlready(quick_check, elm.cp_offset() + j)) continue; + EmitCharacterFunction* emit_function = nullptr; + uc16 quark = quarks[j]; + if (elm.atom()->ignore_case()) { + // Everywhere else we assume that a non-Latin-1 character cannot match + // a Latin-1 character. Avoid the cases where this is assumption is + // invalid by using the Latin1 equivalent instead. + quark = unibrow::Latin1::TryConvertToLatin1(quark); + } + switch (pass) { + case NON_LATIN1_MATCH: + DCHECK(one_byte); + if (quark > String::kMaxOneByteCharCode) { + assembler->GoTo(backtrack); + return; + } + break; + case NON_LETTER_CHARACTER_MATCH: + emit_function = &EmitAtomNonLetter; + break; + case SIMPLE_CHARACTER_MATCH: + emit_function = &EmitSimpleCharacter; + break; + case CASE_CHARACTER_MATCH: + emit_function = &EmitAtomLetter; + break; + default: + break; + } + if (emit_function != nullptr) { + bool bounds_check = *checked_up_to < cp_offset + j || read_backward(); + bool bound_checked = + emit_function(isolate, compiler, quark, backtrack, cp_offset + j, + bounds_check, preloaded); + if (bound_checked) UpdateBoundsCheck(cp_offset + j, checked_up_to); + } + } + } else { + DCHECK_EQ(TextElement::CHAR_CLASS, elm.text_type()); + if (pass == CHARACTER_CLASS_MATCH) { + if (first_element_checked && i == 0) continue; + if (DeterminedAlready(quick_check, elm.cp_offset())) continue; + RegExpCharacterClass* cc = elm.char_class(); + bool bounds_check = *checked_up_to < cp_offset || read_backward(); + EmitCharClass(assembler, cc, one_byte, backtrack, cp_offset, + bounds_check, preloaded, zone()); + UpdateBoundsCheck(cp_offset, checked_up_to); + } + } + } +} + +int TextNode::Length() { + TextElement elm = elements()->last(); + DCHECK_LE(0, elm.cp_offset()); + return elm.cp_offset() + elm.length(); +} + +bool TextNode::SkipPass(TextEmitPassType pass, bool ignore_case) { + if (ignore_case) { + return pass == SIMPLE_CHARACTER_MATCH; + } else { + return pass == NON_LETTER_CHARACTER_MATCH || pass == CASE_CHARACTER_MATCH; + } +} + +TextNode* TextNode::CreateForCharacterRanges(Zone* zone, + ZoneList<CharacterRange>* ranges, + bool read_backward, + RegExpNode* on_success, + JSRegExp::Flags flags) { + DCHECK_NOT_NULL(ranges); + ZoneList<TextElement>* elms = new (zone) ZoneList<TextElement>(1, zone); + elms->Add(TextElement::CharClass( + new (zone) RegExpCharacterClass(zone, ranges, flags)), + zone); + return new (zone) TextNode(elms, read_backward, on_success); +} + +TextNode* TextNode::CreateForSurrogatePair(Zone* zone, CharacterRange lead, + CharacterRange trail, + bool read_backward, + RegExpNode* on_success, + JSRegExp::Flags flags) { + ZoneList<CharacterRange>* lead_ranges = CharacterRange::List(zone, lead); + ZoneList<CharacterRange>* trail_ranges = CharacterRange::List(zone, trail); + ZoneList<TextElement>* elms = new (zone) ZoneList<TextElement>(2, zone); + elms->Add(TextElement::CharClass( + new (zone) RegExpCharacterClass(zone, lead_ranges, flags)), + zone); + elms->Add(TextElement::CharClass( + new (zone) RegExpCharacterClass(zone, trail_ranges, flags)), + zone); + return new (zone) TextNode(elms, read_backward, on_success); +} + +// This generates the code to match a text node. A text node can contain +// straight character sequences (possibly to be matched in a case-independent +// way) and character classes. For efficiency we do not do this in a single +// pass from left to right. Instead we pass over the text node several times, +// emitting code for some character positions every time. See the comment on +// TextEmitPass for details. +void TextNode::Emit(RegExpCompiler* compiler, Trace* trace) { + LimitResult limit_result = LimitVersions(compiler, trace); + if (limit_result == DONE) return; + DCHECK(limit_result == CONTINUE); + + if (trace->cp_offset() + Length() > RegExpMacroAssembler::kMaxCPOffset) { + compiler->SetRegExpTooBig(); + return; + } + + if (compiler->one_byte()) { + int dummy = 0; + TextEmitPass(compiler, NON_LATIN1_MATCH, false, trace, false, &dummy); + } + + bool first_elt_done = false; + int bound_checked_to = trace->cp_offset() - 1; + bound_checked_to += trace->bound_checked_up_to(); + + // If a character is preloaded into the current character register then + // check that now. + if (trace->characters_preloaded() == 1) { + for (int pass = kFirstRealPass; pass <= kLastPass; pass++) { + TextEmitPass(compiler, static_cast<TextEmitPassType>(pass), true, trace, + false, &bound_checked_to); + } + first_elt_done = true; + } + + for (int pass = kFirstRealPass; pass <= kLastPass; pass++) { + TextEmitPass(compiler, static_cast<TextEmitPassType>(pass), false, trace, + first_elt_done, &bound_checked_to); + } + + Trace successor_trace(*trace); + // If we advance backward, we may end up at the start. + successor_trace.AdvanceCurrentPositionInTrace( + read_backward() ? -Length() : Length(), compiler); + successor_trace.set_at_start(read_backward() ? Trace::UNKNOWN + : Trace::FALSE_VALUE); + RecursionCheck rc(compiler); + on_success()->Emit(compiler, &successor_trace); +} + +void Trace::InvalidateCurrentCharacter() { characters_preloaded_ = 0; } + +void Trace::AdvanceCurrentPositionInTrace(int by, RegExpCompiler* compiler) { + // We don't have an instruction for shifting the current character register + // down or for using a shifted value for anything so lets just forget that + // we preloaded any characters into it. + characters_preloaded_ = 0; + // Adjust the offsets of the quick check performed information. This + // information is used to find out what we already determined about the + // characters by means of mask and compare. + quick_check_performed_.Advance(by, compiler->one_byte()); + cp_offset_ += by; + if (cp_offset_ > RegExpMacroAssembler::kMaxCPOffset) { + compiler->SetRegExpTooBig(); + cp_offset_ = 0; + } + bound_checked_up_to_ = Max(0, bound_checked_up_to_ - by); +} + +void TextNode::MakeCaseIndependent(Isolate* isolate, bool is_one_byte) { + int element_count = elements()->length(); + for (int i = 0; i < element_count; i++) { + TextElement elm = elements()->at(i); + if (elm.text_type() == TextElement::CHAR_CLASS) { + RegExpCharacterClass* cc = elm.char_class(); +#ifdef V8_INTL_SUPPORT + bool case_equivalents_already_added = + NeedsUnicodeCaseEquivalents(cc->flags()); +#else + bool case_equivalents_already_added = false; +#endif + if (IgnoreCase(cc->flags()) && !case_equivalents_already_added) { + // None of the standard character classes is different in the case + // independent case and it slows us down if we don't know that. + if (cc->is_standard(zone())) continue; + ZoneList<CharacterRange>* ranges = cc->ranges(zone()); + CharacterRange::AddCaseEquivalents(isolate, zone(), ranges, + is_one_byte); + } + } + } +} + +int TextNode::GreedyLoopTextLength() { return Length(); } + +RegExpNode* TextNode::GetSuccessorOfOmnivorousTextNode( + RegExpCompiler* compiler) { + if (read_backward()) return nullptr; + if (elements()->length() != 1) return nullptr; + TextElement elm = elements()->at(0); + if (elm.text_type() != TextElement::CHAR_CLASS) return nullptr; + RegExpCharacterClass* node = elm.char_class(); + ZoneList<CharacterRange>* ranges = node->ranges(zone()); + CharacterRange::Canonicalize(ranges); + if (node->is_negated()) { + return ranges->length() == 0 ? on_success() : nullptr; + } + if (ranges->length() != 1) return nullptr; + uint32_t max_char; + if (compiler->one_byte()) { + max_char = String::kMaxOneByteCharCode; + } else { + max_char = String::kMaxUtf16CodeUnit; + } + return ranges->at(0).IsEverything(max_char) ? on_success() : nullptr; +} + +// Finds the fixed match length of a sequence of nodes that goes from +// this alternative and back to this choice node. If there are variable +// length nodes or other complications in the way then return a sentinel +// value indicating that a greedy loop cannot be constructed. +int ChoiceNode::GreedyLoopTextLengthForAlternative( + GuardedAlternative* alternative) { + int length = 0; + RegExpNode* node = alternative->node(); + // Later we will generate code for all these text nodes using recursion + // so we have to limit the max number. + int recursion_depth = 0; + while (node != this) { + if (recursion_depth++ > RegExpCompiler::kMaxRecursion) { + return kNodeIsTooComplexForGreedyLoops; + } + int node_length = node->GreedyLoopTextLength(); + if (node_length == kNodeIsTooComplexForGreedyLoops) { + return kNodeIsTooComplexForGreedyLoops; + } + length += node_length; + SeqRegExpNode* seq_node = static_cast<SeqRegExpNode*>(node); + node = seq_node->on_success(); + } + return read_backward() ? -length : length; +} + +void LoopChoiceNode::AddLoopAlternative(GuardedAlternative alt) { + DCHECK_NULL(loop_node_); + AddAlternative(alt); + loop_node_ = alt.node(); +} + +void LoopChoiceNode::AddContinueAlternative(GuardedAlternative alt) { + DCHECK_NULL(continue_node_); + AddAlternative(alt); + continue_node_ = alt.node(); +} + +void LoopChoiceNode::Emit(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + if (trace->stop_node() == this) { + // Back edge of greedy optimized loop node graph. + int text_length = + GreedyLoopTextLengthForAlternative(&(alternatives_->at(0))); + DCHECK_NE(kNodeIsTooComplexForGreedyLoops, text_length); + // Update the counter-based backtracking info on the stack. This is an + // optimization for greedy loops (see below). + DCHECK(trace->cp_offset() == text_length); + macro_assembler->AdvanceCurrentPosition(text_length); + macro_assembler->GoTo(trace->loop_label()); + return; + } + DCHECK_NULL(trace->stop_node()); + if (!trace->is_trivial()) { + trace->Flush(compiler, this); + return; + } + ChoiceNode::Emit(compiler, trace); +} + +int ChoiceNode::CalculatePreloadCharacters(RegExpCompiler* compiler, + int eats_at_least) { + int preload_characters = Min(4, eats_at_least); + DCHECK_LE(preload_characters, 4); + if (compiler->macro_assembler()->CanReadUnaligned()) { + bool one_byte = compiler->one_byte(); + if (one_byte) { + // We can't preload 3 characters because there is no machine instruction + // to do that. We can't just load 4 because we could be reading + // beyond the end of the string, which could cause a memory fault. + if (preload_characters == 3) preload_characters = 2; + } else { + if (preload_characters > 2) preload_characters = 2; + } + } else { + if (preload_characters > 1) preload_characters = 1; + } + return preload_characters; +} + +// This class is used when generating the alternatives in a choice node. It +// records the way the alternative is being code generated. +class AlternativeGeneration : public Malloced { + public: + AlternativeGeneration() + : possible_success(), + expects_preload(false), + after(), + quick_check_details() {} + Label possible_success; + bool expects_preload; + Label after; + QuickCheckDetails quick_check_details; +}; + +// Creates a list of AlternativeGenerations. If the list has a reasonable +// size then it is on the stack, otherwise the excess is on the heap. +class AlternativeGenerationList { + public: + AlternativeGenerationList(int count, Zone* zone) : alt_gens_(count, zone) { + for (int i = 0; i < count && i < kAFew; i++) { + alt_gens_.Add(a_few_alt_gens_ + i, zone); + } + for (int i = kAFew; i < count; i++) { + alt_gens_.Add(new AlternativeGeneration(), zone); + } + } + ~AlternativeGenerationList() { + for (int i = kAFew; i < alt_gens_.length(); i++) { + delete alt_gens_[i]; + alt_gens_[i] = nullptr; + } + } + + AlternativeGeneration* at(int i) { return alt_gens_[i]; } + + private: + static const int kAFew = 10; + ZoneList<AlternativeGeneration*> alt_gens_; + AlternativeGeneration a_few_alt_gens_[kAFew]; +}; + +void BoyerMoorePositionInfo::Set(int character) { + SetInterval(Interval(character, character)); +} + +namespace { + +ContainedInLattice AddRange(ContainedInLattice containment, const int* ranges, + int ranges_length, Interval new_range) { + DCHECK_EQ(1, ranges_length & 1); + DCHECK_EQ(String::kMaxCodePoint + 1, ranges[ranges_length - 1]); + if (containment == kLatticeUnknown) return containment; + bool inside = false; + int last = 0; + for (int i = 0; i < ranges_length; inside = !inside, last = ranges[i], i++) { + // Consider the range from last to ranges[i]. + // We haven't got to the new range yet. + if (ranges[i] <= new_range.from()) continue; + // New range is wholly inside last-ranges[i]. Note that new_range.to() is + // inclusive, but the values in ranges are not. + if (last <= new_range.from() && new_range.to() < ranges[i]) { + return Combine(containment, inside ? kLatticeIn : kLatticeOut); + } + return kLatticeUnknown; + } + return containment; +} + +int BitsetFirstSetBit(BoyerMoorePositionInfo::Bitset bitset) { + STATIC_ASSERT(BoyerMoorePositionInfo::kMapSize == + 2 * kInt64Size * kBitsPerByte); + + // Slight fiddling is needed here, since the bitset is of length 128 while + // CountTrailingZeros requires an integral type and std::bitset can only + // convert to unsigned long long. So we handle the most- and least-significant + // bits separately. + + { + static constexpr BoyerMoorePositionInfo::Bitset mask(~uint64_t{0}); + BoyerMoorePositionInfo::Bitset masked_bitset = bitset & mask; + STATIC_ASSERT(kInt64Size >= sizeof(decltype(masked_bitset.to_ullong()))); + uint64_t lsb = masked_bitset.to_ullong(); + if (lsb != 0) return base::bits::CountTrailingZeros(lsb); + } + + { + BoyerMoorePositionInfo::Bitset masked_bitset = bitset >> 64; + uint64_t msb = masked_bitset.to_ullong(); + if (msb != 0) return 64 + base::bits::CountTrailingZeros(msb); + } + + return -1; +} + +} // namespace + +void BoyerMoorePositionInfo::SetInterval(const Interval& interval) { + w_ = AddRange(w_, kWordRanges, kWordRangeCount, interval); + + if (interval.size() >= kMapSize) { + map_count_ = kMapSize; + map_.set(); + return; + } + + for (int i = interval.from(); i <= interval.to(); i++) { + int mod_character = (i & kMask); + if (!map_[mod_character]) { + map_count_++; + map_.set(mod_character); + } + if (map_count_ == kMapSize) return; + } +} + +void BoyerMoorePositionInfo::SetAll() { + w_ = kLatticeUnknown; + if (map_count_ != kMapSize) { + map_count_ = kMapSize; + map_.set(); + } +} + +BoyerMooreLookahead::BoyerMooreLookahead(int length, RegExpCompiler* compiler, + Zone* zone) + : length_(length), compiler_(compiler) { + if (compiler->one_byte()) { + max_char_ = String::kMaxOneByteCharCode; + } else { + max_char_ = String::kMaxUtf16CodeUnit; + } + bitmaps_ = new (zone) ZoneList<BoyerMoorePositionInfo*>(length, zone); + for (int i = 0; i < length; i++) { + bitmaps_->Add(new (zone) BoyerMoorePositionInfo(), zone); + } +} + +// Find the longest range of lookahead that has the fewest number of different +// characters that can occur at a given position. Since we are optimizing two +// different parameters at once this is a tradeoff. +bool BoyerMooreLookahead::FindWorthwhileInterval(int* from, int* to) { + int biggest_points = 0; + // If more than 32 characters out of 128 can occur it is unlikely that we can + // be lucky enough to step forwards much of the time. + const int kMaxMax = 32; + for (int max_number_of_chars = 4; max_number_of_chars < kMaxMax; + max_number_of_chars *= 2) { + biggest_points = + FindBestInterval(max_number_of_chars, biggest_points, from, to); + } + if (biggest_points == 0) return false; + return true; +} + +// Find the highest-points range between 0 and length_ where the character +// information is not too vague. 'Too vague' means that there are more than +// max_number_of_chars that can occur at this position. Calculates the number +// of points as the product of width-of-the-range and +// probability-of-finding-one-of-the-characters, where the probability is +// calculated using the frequency distribution of the sample subject string. +int BoyerMooreLookahead::FindBestInterval(int max_number_of_chars, + int old_biggest_points, int* from, + int* to) { + int biggest_points = old_biggest_points; + static const int kSize = RegExpMacroAssembler::kTableSize; + for (int i = 0; i < length_;) { + while (i < length_ && Count(i) > max_number_of_chars) i++; + if (i == length_) break; + int remembered_from = i; + + BoyerMoorePositionInfo::Bitset union_bitset; + for (; i < length_ && Count(i) <= max_number_of_chars; i++) { + union_bitset |= bitmaps_->at(i)->raw_bitset(); + } + + int frequency = 0; + + // Iterate only over set bits. + int j; + while ((j = BitsetFirstSetBit(union_bitset)) != -1) { + DCHECK(union_bitset[j]); // Sanity check. + // Add 1 to the frequency to give a small per-character boost for + // the cases where our sampling is not good enough and many + // characters have a frequency of zero. This means the frequency + // can theoretically be up to 2*kSize though we treat it mostly as + // a fraction of kSize. + frequency += compiler_->frequency_collator()->Frequency(j) + 1; + union_bitset.reset(j); + } + + // We use the probability of skipping times the distance we are skipping to + // judge the effectiveness of this. Actually we have a cut-off: By + // dividing by 2 we switch off the skipping if the probability of skipping + // is less than 50%. This is because the multibyte mask-and-compare + // skipping in quickcheck is more likely to do well on this case. + bool in_quickcheck_range = + ((i - remembered_from < 4) || + (compiler_->one_byte() ? remembered_from <= 4 : remembered_from <= 2)); + // Called 'probability' but it is only a rough estimate and can actually + // be outside the 0-kSize range. + int probability = (in_quickcheck_range ? kSize / 2 : kSize) - frequency; + int points = (i - remembered_from) * probability; + if (points > biggest_points) { + *from = remembered_from; + *to = i - 1; + biggest_points = points; + } + } + return biggest_points; +} + +// Take all the characters that will not prevent a successful match if they +// occur in the subject string in the range between min_lookahead and +// max_lookahead (inclusive) measured from the current position. If the +// character at max_lookahead offset is not one of these characters, then we +// can safely skip forwards by the number of characters in the range. +int BoyerMooreLookahead::GetSkipTable(int min_lookahead, int max_lookahead, + Handle<ByteArray> boolean_skip_table) { + const int kSkipArrayEntry = 0; + const int kDontSkipArrayEntry = 1; + + std::memset(boolean_skip_table->GetDataStartAddress(), kSkipArrayEntry, + boolean_skip_table->length()); + + for (int i = max_lookahead; i >= min_lookahead; i--) { + BoyerMoorePositionInfo::Bitset bitset = bitmaps_->at(i)->raw_bitset(); + + // Iterate only over set bits. + int j; + while ((j = BitsetFirstSetBit(bitset)) != -1) { + DCHECK(bitset[j]); // Sanity check. + boolean_skip_table->set(j, kDontSkipArrayEntry); + bitset.reset(j); + } + } + + const int skip = max_lookahead + 1 - min_lookahead; + return skip; +} + +// See comment above on the implementation of GetSkipTable. +void BoyerMooreLookahead::EmitSkipInstructions(RegExpMacroAssembler* masm) { + const int kSize = RegExpMacroAssembler::kTableSize; + + int min_lookahead = 0; + int max_lookahead = 0; + + if (!FindWorthwhileInterval(&min_lookahead, &max_lookahead)) return; + + // Check if we only have a single non-empty position info, and that info + // contains precisely one character. + bool found_single_character = false; + int single_character = 0; + for (int i = max_lookahead; i >= min_lookahead; i--) { + BoyerMoorePositionInfo* map = bitmaps_->at(i); + if (map->map_count() == 0) continue; + + if (found_single_character || map->map_count() > 1) { + found_single_character = false; + break; + } + + DCHECK(!found_single_character); + DCHECK_EQ(map->map_count(), 1); + + found_single_character = true; + single_character = BitsetFirstSetBit(map->raw_bitset()); + + DCHECK_NE(single_character, -1); + } + + int lookahead_width = max_lookahead + 1 - min_lookahead; + + if (found_single_character && lookahead_width == 1 && max_lookahead < 3) { + // The mask-compare can probably handle this better. + return; + } + + if (found_single_character) { + Label cont, again; + masm->Bind(&again); + masm->LoadCurrentCharacter(max_lookahead, &cont, true); + if (max_char_ > kSize) { + masm->CheckCharacterAfterAnd(single_character, + RegExpMacroAssembler::kTableMask, &cont); + } else { + masm->CheckCharacter(single_character, &cont); + } + masm->AdvanceCurrentPosition(lookahead_width); + masm->GoTo(&again); + masm->Bind(&cont); + return; + } + + Factory* factory = masm->isolate()->factory(); + Handle<ByteArray> boolean_skip_table = + factory->NewByteArray(kSize, AllocationType::kOld); + int skip_distance = + GetSkipTable(min_lookahead, max_lookahead, boolean_skip_table); + DCHECK_NE(0, skip_distance); + + Label cont, again; + masm->Bind(&again); + masm->LoadCurrentCharacter(max_lookahead, &cont, true); + masm->CheckBitInTable(boolean_skip_table, &cont); + masm->AdvanceCurrentPosition(skip_distance); + masm->GoTo(&again); + masm->Bind(&cont); +} + +/* Code generation for choice nodes. + * + * We generate quick checks that do a mask and compare to eliminate a + * choice. If the quick check succeeds then it jumps to the continuation to + * do slow checks and check subsequent nodes. If it fails (the common case) + * it falls through to the next choice. + * + * Here is the desired flow graph. Nodes directly below each other imply + * fallthrough. Alternatives 1 and 2 have quick checks. Alternative + * 3 doesn't have a quick check so we have to call the slow check. + * Nodes are marked Qn for quick checks and Sn for slow checks. The entire + * regexp continuation is generated directly after the Sn node, up to the + * next GoTo if we decide to reuse some already generated code. Some + * nodes expect preload_characters to be preloaded into the current + * character register. R nodes do this preloading. Vertices are marked + * F for failures and S for success (possible success in the case of quick + * nodes). L, V, < and > are used as arrow heads. + * + * ----------> R + * | + * V + * Q1 -----> S1 + * | S / + * F| / + * | F/ + * | / + * | R + * | / + * V L + * Q2 -----> S2 + * | S / + * F| / + * | F/ + * | / + * | R + * | / + * V L + * S3 + * | + * F| + * | + * R + * | + * backtrack V + * <----------Q4 + * \ F | + * \ |S + * \ F V + * \-----S4 + * + * For greedy loops we push the current position, then generate the code that + * eats the input specially in EmitGreedyLoop. The other choice (the + * continuation) is generated by the normal code in EmitChoices, and steps back + * in the input to the starting position when it fails to match. The loop code + * looks like this (U is the unwind code that steps back in the greedy loop). + * + * _____ + * / \ + * V | + * ----------> S1 | + * /| | + * / |S | + * F/ \_____/ + * / + * |<----- + * | \ + * V |S + * Q2 ---> U----->backtrack + * | F / + * S| / + * V F / + * S2--/ + */ + +GreedyLoopState::GreedyLoopState(bool not_at_start) { + counter_backtrack_trace_.set_backtrack(&label_); + if (not_at_start) counter_backtrack_trace_.set_at_start(Trace::FALSE_VALUE); +} + +void ChoiceNode::AssertGuardsMentionRegisters(Trace* trace) { +#ifdef DEBUG + int choice_count = alternatives_->length(); + for (int i = 0; i < choice_count - 1; i++) { + GuardedAlternative alternative = alternatives_->at(i); + ZoneList<Guard*>* guards = alternative.guards(); + int guard_count = (guards == nullptr) ? 0 : guards->length(); + for (int j = 0; j < guard_count; j++) { + DCHECK(!trace->mentions_reg(guards->at(j)->reg())); + } + } +#endif +} + +void ChoiceNode::SetUpPreLoad(RegExpCompiler* compiler, Trace* current_trace, + PreloadState* state) { + if (state->eats_at_least_ == PreloadState::kEatsAtLeastNotYetInitialized) { + // Save some time by looking at most one machine word ahead. + state->eats_at_least_ = + EatsAtLeast(current_trace->at_start() == Trace::FALSE_VALUE); + } + state->preload_characters_ = + CalculatePreloadCharacters(compiler, state->eats_at_least_); + + state->preload_is_current_ = + (current_trace->characters_preloaded() == state->preload_characters_); + state->preload_has_checked_bounds_ = state->preload_is_current_; +} + +void ChoiceNode::Emit(RegExpCompiler* compiler, Trace* trace) { + int choice_count = alternatives_->length(); + + if (choice_count == 1 && alternatives_->at(0).guards() == nullptr) { + alternatives_->at(0).node()->Emit(compiler, trace); + return; + } + + AssertGuardsMentionRegisters(trace); + + LimitResult limit_result = LimitVersions(compiler, trace); + if (limit_result == DONE) return; + DCHECK(limit_result == CONTINUE); + + // For loop nodes we already flushed (see LoopChoiceNode::Emit), but for + // other choice nodes we only flush if we are out of code size budget. + if (trace->flush_budget() == 0 && trace->actions() != nullptr) { + trace->Flush(compiler, this); + return; + } + + RecursionCheck rc(compiler); + + PreloadState preload; + preload.init(); + GreedyLoopState greedy_loop_state(not_at_start()); + + int text_length = GreedyLoopTextLengthForAlternative(&alternatives_->at(0)); + AlternativeGenerationList alt_gens(choice_count, zone()); + + if (choice_count > 1 && text_length != kNodeIsTooComplexForGreedyLoops) { + trace = EmitGreedyLoop(compiler, trace, &alt_gens, &preload, + &greedy_loop_state, text_length); + } else { + // TODO(erikcorry): Delete this. We don't need this label, but it makes us + // match the traces produced pre-cleanup. + Label second_choice; + compiler->macro_assembler()->Bind(&second_choice); + + preload.eats_at_least_ = EmitOptimizedUnanchoredSearch(compiler, trace); + + EmitChoices(compiler, &alt_gens, 0, trace, &preload); + } + + // At this point we need to generate slow checks for the alternatives where + // the quick check was inlined. We can recognize these because the associated + // label was bound. + int new_flush_budget = trace->flush_budget() / choice_count; + for (int i = 0; i < choice_count; i++) { + AlternativeGeneration* alt_gen = alt_gens.at(i); + Trace new_trace(*trace); + // If there are actions to be flushed we have to limit how many times + // they are flushed. Take the budget of the parent trace and distribute + // it fairly amongst the children. + if (new_trace.actions() != nullptr) { + new_trace.set_flush_budget(new_flush_budget); + } + bool next_expects_preload = + i == choice_count - 1 ? false : alt_gens.at(i + 1)->expects_preload; + EmitOutOfLineContinuation(compiler, &new_trace, alternatives_->at(i), + alt_gen, preload.preload_characters_, + next_expects_preload); + } +} + +Trace* ChoiceNode::EmitGreedyLoop(RegExpCompiler* compiler, Trace* trace, + AlternativeGenerationList* alt_gens, + PreloadState* preload, + GreedyLoopState* greedy_loop_state, + int text_length) { + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + // Here we have special handling for greedy loops containing only text nodes + // and other simple nodes. These are handled by pushing the current + // position on the stack and then incrementing the current position each + // time around the switch. On backtrack we decrement the current position + // and check it against the pushed value. This avoids pushing backtrack + // information for each iteration of the loop, which could take up a lot of + // space. + DCHECK(trace->stop_node() == nullptr); + macro_assembler->PushCurrentPosition(); + Label greedy_match_failed; + Trace greedy_match_trace; + if (not_at_start()) greedy_match_trace.set_at_start(Trace::FALSE_VALUE); + greedy_match_trace.set_backtrack(&greedy_match_failed); + Label loop_label; + macro_assembler->Bind(&loop_label); + greedy_match_trace.set_stop_node(this); + greedy_match_trace.set_loop_label(&loop_label); + alternatives_->at(0).node()->Emit(compiler, &greedy_match_trace); + macro_assembler->Bind(&greedy_match_failed); + + Label second_choice; // For use in greedy matches. + macro_assembler->Bind(&second_choice); + + Trace* new_trace = greedy_loop_state->counter_backtrack_trace(); + + EmitChoices(compiler, alt_gens, 1, new_trace, preload); + + macro_assembler->Bind(greedy_loop_state->label()); + // If we have unwound to the bottom then backtrack. + macro_assembler->CheckGreedyLoop(trace->backtrack()); + // Otherwise try the second priority at an earlier position. + macro_assembler->AdvanceCurrentPosition(-text_length); + macro_assembler->GoTo(&second_choice); + return new_trace; +} + +int ChoiceNode::EmitOptimizedUnanchoredSearch(RegExpCompiler* compiler, + Trace* trace) { + int eats_at_least = PreloadState::kEatsAtLeastNotYetInitialized; + if (alternatives_->length() != 2) return eats_at_least; + + GuardedAlternative alt1 = alternatives_->at(1); + if (alt1.guards() != nullptr && alt1.guards()->length() != 0) { + return eats_at_least; + } + RegExpNode* eats_anything_node = alt1.node(); + if (eats_anything_node->GetSuccessorOfOmnivorousTextNode(compiler) != this) { + return eats_at_least; + } + + // Really we should be creating a new trace when we execute this function, + // but there is no need, because the code it generates cannot backtrack, and + // we always arrive here with a trivial trace (since it's the entry to a + // loop. That also implies that there are no preloaded characters, which is + // good, because it means we won't be violating any assumptions by + // overwriting those characters with new load instructions. + DCHECK(trace->is_trivial()); + + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + Isolate* isolate = macro_assembler->isolate(); + // At this point we know that we are at a non-greedy loop that will eat + // any character one at a time. Any non-anchored regexp has such a + // loop prepended to it in order to find where it starts. We look for + // a pattern of the form ...abc... where we can look 6 characters ahead + // and step forwards 3 if the character is not one of abc. Abc need + // not be atoms, they can be any reasonably limited character class or + // small alternation. + BoyerMooreLookahead* bm = bm_info(false); + if (bm == nullptr) { + eats_at_least = Min(kMaxLookaheadForBoyerMoore, EatsAtLeast(false)); + if (eats_at_least >= 1) { + bm = new (zone()) BoyerMooreLookahead(eats_at_least, compiler, zone()); + GuardedAlternative alt0 = alternatives_->at(0); + alt0.node()->FillInBMInfo(isolate, 0, kRecursionBudget, bm, false); + } + } + if (bm != nullptr) { + bm->EmitSkipInstructions(macro_assembler); + } + return eats_at_least; +} + +void ChoiceNode::EmitChoices(RegExpCompiler* compiler, + AlternativeGenerationList* alt_gens, + int first_choice, Trace* trace, + PreloadState* preload) { + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + SetUpPreLoad(compiler, trace, preload); + + // For now we just call all choices one after the other. The idea ultimately + // is to use the Dispatch table to try only the relevant ones. + int choice_count = alternatives_->length(); + + int new_flush_budget = trace->flush_budget() / choice_count; + + for (int i = first_choice; i < choice_count; i++) { + bool is_last = i == choice_count - 1; + bool fall_through_on_failure = !is_last; + GuardedAlternative alternative = alternatives_->at(i); + AlternativeGeneration* alt_gen = alt_gens->at(i); + alt_gen->quick_check_details.set_characters(preload->preload_characters_); + ZoneList<Guard*>* guards = alternative.guards(); + int guard_count = (guards == nullptr) ? 0 : guards->length(); + Trace new_trace(*trace); + new_trace.set_characters_preloaded( + preload->preload_is_current_ ? preload->preload_characters_ : 0); + if (preload->preload_has_checked_bounds_) { + new_trace.set_bound_checked_up_to(preload->preload_characters_); + } + new_trace.quick_check_performed()->Clear(); + if (not_at_start_) new_trace.set_at_start(Trace::FALSE_VALUE); + if (!is_last) { + new_trace.set_backtrack(&alt_gen->after); + } + alt_gen->expects_preload = preload->preload_is_current_; + bool generate_full_check_inline = false; + if (compiler->optimize() && + try_to_emit_quick_check_for_alternative(i == 0) && + alternative.node()->EmitQuickCheck( + compiler, trace, &new_trace, preload->preload_has_checked_bounds_, + &alt_gen->possible_success, &alt_gen->quick_check_details, + fall_through_on_failure, this)) { + // Quick check was generated for this choice. + preload->preload_is_current_ = true; + preload->preload_has_checked_bounds_ = true; + // If we generated the quick check to fall through on possible success, + // we now need to generate the full check inline. + if (!fall_through_on_failure) { + macro_assembler->Bind(&alt_gen->possible_success); + new_trace.set_quick_check_performed(&alt_gen->quick_check_details); + new_trace.set_characters_preloaded(preload->preload_characters_); + new_trace.set_bound_checked_up_to(preload->preload_characters_); + generate_full_check_inline = true; + } + } else if (alt_gen->quick_check_details.cannot_match()) { + if (!fall_through_on_failure) { + macro_assembler->GoTo(trace->backtrack()); + } + continue; + } else { + // No quick check was generated. Put the full code here. + // If this is not the first choice then there could be slow checks from + // previous cases that go here when they fail. There's no reason to + // insist that they preload characters since the slow check we are about + // to generate probably can't use it. + if (i != first_choice) { + alt_gen->expects_preload = false; + new_trace.InvalidateCurrentCharacter(); + } + generate_full_check_inline = true; + } + if (generate_full_check_inline) { + if (new_trace.actions() != nullptr) { + new_trace.set_flush_budget(new_flush_budget); + } + for (int j = 0; j < guard_count; j++) { + GenerateGuard(macro_assembler, guards->at(j), &new_trace); + } + alternative.node()->Emit(compiler, &new_trace); + preload->preload_is_current_ = false; + } + macro_assembler->Bind(&alt_gen->after); + } +} + +void ChoiceNode::EmitOutOfLineContinuation(RegExpCompiler* compiler, + Trace* trace, + GuardedAlternative alternative, + AlternativeGeneration* alt_gen, + int preload_characters, + bool next_expects_preload) { + if (!alt_gen->possible_success.is_linked()) return; + + RegExpMacroAssembler* macro_assembler = compiler->macro_assembler(); + macro_assembler->Bind(&alt_gen->possible_success); + Trace out_of_line_trace(*trace); + out_of_line_trace.set_characters_preloaded(preload_characters); + out_of_line_trace.set_quick_check_performed(&alt_gen->quick_check_details); + if (not_at_start_) out_of_line_trace.set_at_start(Trace::FALSE_VALUE); + ZoneList<Guard*>* guards = alternative.guards(); + int guard_count = (guards == nullptr) ? 0 : guards->length(); + if (next_expects_preload) { + Label reload_current_char; + out_of_line_trace.set_backtrack(&reload_current_char); + for (int j = 0; j < guard_count; j++) { + GenerateGuard(macro_assembler, guards->at(j), &out_of_line_trace); + } + alternative.node()->Emit(compiler, &out_of_line_trace); + macro_assembler->Bind(&reload_current_char); + // Reload the current character, since the next quick check expects that. + // We don't need to check bounds here because we only get into this + // code through a quick check which already did the checked load. + macro_assembler->LoadCurrentCharacter(trace->cp_offset(), nullptr, false, + preload_characters); + macro_assembler->GoTo(&(alt_gen->after)); + } else { + out_of_line_trace.set_backtrack(&(alt_gen->after)); + for (int j = 0; j < guard_count; j++) { + GenerateGuard(macro_assembler, guards->at(j), &out_of_line_trace); + } + alternative.node()->Emit(compiler, &out_of_line_trace); + } +} + +void ActionNode::Emit(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + LimitResult limit_result = LimitVersions(compiler, trace); + if (limit_result == DONE) return; + DCHECK(limit_result == CONTINUE); + + RecursionCheck rc(compiler); + + switch (action_type_) { + case STORE_POSITION: { + Trace::DeferredCapture new_capture(data_.u_position_register.reg, + data_.u_position_register.is_capture, + trace); + Trace new_trace = *trace; + new_trace.add_action(&new_capture); + on_success()->Emit(compiler, &new_trace); + break; + } + case INCREMENT_REGISTER: { + Trace::DeferredIncrementRegister new_increment( + data_.u_increment_register.reg); + Trace new_trace = *trace; + new_trace.add_action(&new_increment); + on_success()->Emit(compiler, &new_trace); + break; + } + case SET_REGISTER_FOR_LOOP: { + Trace::DeferredSetRegisterForLoop new_set(data_.u_store_register.reg, + data_.u_store_register.value); + Trace new_trace = *trace; + new_trace.add_action(&new_set); + on_success()->Emit(compiler, &new_trace); + break; + } + case CLEAR_CAPTURES: { + Trace::DeferredClearCaptures new_capture(Interval( + data_.u_clear_captures.range_from, data_.u_clear_captures.range_to)); + Trace new_trace = *trace; + new_trace.add_action(&new_capture); + on_success()->Emit(compiler, &new_trace); + break; + } + case BEGIN_SUBMATCH: + if (!trace->is_trivial()) { + trace->Flush(compiler, this); + } else { + assembler->WriteCurrentPositionToRegister( + data_.u_submatch.current_position_register, 0); + assembler->WriteStackPointerToRegister( + data_.u_submatch.stack_pointer_register); + on_success()->Emit(compiler, trace); + } + break; + case EMPTY_MATCH_CHECK: { + int start_pos_reg = data_.u_empty_match_check.start_register; + int stored_pos = 0; + int rep_reg = data_.u_empty_match_check.repetition_register; + bool has_minimum = (rep_reg != RegExpCompiler::kNoRegister); + bool know_dist = trace->GetStoredPosition(start_pos_reg, &stored_pos); + if (know_dist && !has_minimum && stored_pos == trace->cp_offset()) { + // If we know we haven't advanced and there is no minimum we + // can just backtrack immediately. + assembler->GoTo(trace->backtrack()); + } else if (know_dist && stored_pos < trace->cp_offset()) { + // If we know we've advanced we can generate the continuation + // immediately. + on_success()->Emit(compiler, trace); + } else if (!trace->is_trivial()) { + trace->Flush(compiler, this); + } else { + Label skip_empty_check; + // If we have a minimum number of repetitions we check the current + // number first and skip the empty check if it's not enough. + if (has_minimum) { + int limit = data_.u_empty_match_check.repetition_limit; + assembler->IfRegisterLT(rep_reg, limit, &skip_empty_check); + } + // If the match is empty we bail out, otherwise we fall through + // to the on-success continuation. + assembler->IfRegisterEqPos(data_.u_empty_match_check.start_register, + trace->backtrack()); + assembler->Bind(&skip_empty_check); + on_success()->Emit(compiler, trace); + } + break; + } + case POSITIVE_SUBMATCH_SUCCESS: { + if (!trace->is_trivial()) { + trace->Flush(compiler, this); + return; + } + assembler->ReadCurrentPositionFromRegister( + data_.u_submatch.current_position_register); + assembler->ReadStackPointerFromRegister( + data_.u_submatch.stack_pointer_register); + int clear_register_count = data_.u_submatch.clear_register_count; + if (clear_register_count == 0) { + on_success()->Emit(compiler, trace); + return; + } + int clear_registers_from = data_.u_submatch.clear_register_from; + Label clear_registers_backtrack; + Trace new_trace = *trace; + new_trace.set_backtrack(&clear_registers_backtrack); + on_success()->Emit(compiler, &new_trace); + + assembler->Bind(&clear_registers_backtrack); + int clear_registers_to = clear_registers_from + clear_register_count - 1; + assembler->ClearRegisters(clear_registers_from, clear_registers_to); + + DCHECK(trace->backtrack() == nullptr); + assembler->Backtrack(); + return; + } + default: + UNREACHABLE(); + } +} + +void BackReferenceNode::Emit(RegExpCompiler* compiler, Trace* trace) { + RegExpMacroAssembler* assembler = compiler->macro_assembler(); + if (!trace->is_trivial()) { + trace->Flush(compiler, this); + return; + } + + LimitResult limit_result = LimitVersions(compiler, trace); + if (limit_result == DONE) return; + DCHECK(limit_result == CONTINUE); + + RecursionCheck rc(compiler); + + DCHECK_EQ(start_reg_ + 1, end_reg_); + if (IgnoreCase(flags_)) { + assembler->CheckNotBackReferenceIgnoreCase( + start_reg_, read_backward(), IsUnicode(flags_), trace->backtrack()); + } else { + assembler->CheckNotBackReference(start_reg_, read_backward(), + trace->backtrack()); + } + // We are going to advance backward, so we may end up at the start. + if (read_backward()) trace->set_at_start(Trace::UNKNOWN); + + // Check that the back reference does not end inside a surrogate pair. + if (IsUnicode(flags_) && !compiler->one_byte()) { + assembler->CheckNotInSurrogatePair(trace->cp_offset(), trace->backtrack()); + } + on_success()->Emit(compiler, trace); +} + +void TextNode::CalculateOffsets() { + int element_count = elements()->length(); + // Set up the offsets of the elements relative to the start. This is a fixed + // quantity since a TextNode can only contain fixed-width things. + int cp_offset = 0; + for (int i = 0; i < element_count; i++) { + TextElement& elm = elements()->at(i); + elm.set_cp_offset(cp_offset); + cp_offset += elm.length(); + } +} + +namespace { + +// Assertion propagation moves information about assertions such as +// \b to the affected nodes. For instance, in /.\b./ information must +// be propagated to the first '.' that whatever follows needs to know +// if it matched a word or a non-word, and to the second '.' that it +// has to check if it succeeds a word or non-word. In this case the +// result will be something like: +// +// +-------+ +------------+ +// | . | | . | +// +-------+ ---> +------------+ +// | word? | | check word | +// +-------+ +------------+ +class AssertionPropagator : public AllStatic { + public: + static void VisitText(TextNode* that) {} + + static void VisitAction(ActionNode* that) { + // If the next node is interested in what it follows then this node + // has to be interested too so it can pass the information on. + that->info()->AddFromFollowing(that->on_success()->info()); + } + + static void VisitChoice(ChoiceNode* that, int i) { + // Anything the following nodes need to know has to be known by + // this node also, so it can pass it on. + that->info()->AddFromFollowing(that->alternatives()->at(i).node()->info()); + } + + static void VisitLoopChoiceContinueNode(LoopChoiceNode* that) { + that->info()->AddFromFollowing(that->continue_node()->info()); + } + + static void VisitLoopChoiceLoopNode(LoopChoiceNode* that) { + that->info()->AddFromFollowing(that->loop_node()->info()); + } + + static void VisitNegativeLookaroundChoiceLookaroundNode( + NegativeLookaroundChoiceNode* that) { + VisitChoice(that, NegativeLookaroundChoiceNode::kLookaroundIndex); + } + + static void VisitNegativeLookaroundChoiceContinueNode( + NegativeLookaroundChoiceNode* that) { + VisitChoice(that, NegativeLookaroundChoiceNode::kContinueIndex); + } + + static void VisitBackReference(BackReferenceNode* that) {} + + static void VisitAssertion(AssertionNode* that) {} +}; + +// Propagates information about the minimum size of successful matches from +// successor nodes to their predecessors. Note that all eats_at_least values +// are initialized to zero before analysis. +class EatsAtLeastPropagator : public AllStatic { + public: + static void VisitText(TextNode* that) { + // The eats_at_least value is not used if reading backward. + if (!that->read_backward()) { + // We are not at the start after this node, and thus we can use the + // successor's eats_at_least_from_not_start value. + uint8_t eats_at_least = base::saturated_cast<uint8_t>( + that->Length() + that->on_success() + ->eats_at_least_info() + ->eats_at_least_from_not_start); + that->set_eats_at_least_info(EatsAtLeastInfo(eats_at_least)); + } + } + + static void VisitAction(ActionNode* that) { + // POSITIVE_SUBMATCH_SUCCESS rewinds input, so we must not consider + // successor nodes for eats_at_least. SET_REGISTER_FOR_LOOP indicates a loop + // entry point, which means the loop body will run at least the minimum + // number of times before the continuation case can run. Otherwise the + // current node eats at least as much as its successor. + switch (that->action_type()) { + case ActionNode::POSITIVE_SUBMATCH_SUCCESS: + break; // Was already initialized to zero. + case ActionNode::SET_REGISTER_FOR_LOOP: + that->set_eats_at_least_info( + that->on_success()->EatsAtLeastFromLoopEntry()); + break; + default: + that->set_eats_at_least_info(*that->on_success()->eats_at_least_info()); + break; + } + } + + static void VisitChoice(ChoiceNode* that, int i) { + // The minimum possible match from a choice node is the minimum of its + // successors. + EatsAtLeastInfo eats_at_least = + i == 0 ? EatsAtLeastInfo(UINT8_MAX) : *that->eats_at_least_info(); + eats_at_least.SetMin( + *that->alternatives()->at(i).node()->eats_at_least_info()); + that->set_eats_at_least_info(eats_at_least); + } + + static void VisitLoopChoiceContinueNode(LoopChoiceNode* that) { + that->set_eats_at_least_info(*that->continue_node()->eats_at_least_info()); + } + + static void VisitLoopChoiceLoopNode(LoopChoiceNode* that) {} + + static void VisitNegativeLookaroundChoiceLookaroundNode( + NegativeLookaroundChoiceNode* that) {} + + static void VisitNegativeLookaroundChoiceContinueNode( + NegativeLookaroundChoiceNode* that) { + that->set_eats_at_least_info(*that->continue_node()->eats_at_least_info()); + } + + static void VisitBackReference(BackReferenceNode* that) { + if (!that->read_backward()) { + that->set_eats_at_least_info(*that->on_success()->eats_at_least_info()); + } + } + + static void VisitAssertion(AssertionNode* that) { + EatsAtLeastInfo eats_at_least = *that->on_success()->eats_at_least_info(); + if (that->assertion_type() == AssertionNode::AT_START) { + // If we know we are not at the start and we are asked "how many + // characters will you match if you succeed?" then we can answer anything + // since false implies false. So let's just set the max answer + // (UINT8_MAX) since that won't prevent us from preloading a lot of + // characters for the other branches in the node graph. + eats_at_least.eats_at_least_from_not_start = UINT8_MAX; + } + that->set_eats_at_least_info(eats_at_least); + } +}; + +} // namespace + +// ------------------------------------------------------------------- +// Analysis + +// Iterates the node graph and provides the opportunity for propagators to set +// values that depend on successor nodes. +template <typename... Propagators> +class Analysis : public NodeVisitor { + public: + Analysis(Isolate* isolate, bool is_one_byte) + : isolate_(isolate), is_one_byte_(is_one_byte), error_message_(nullptr) {} + + void EnsureAnalyzed(RegExpNode* that) { + StackLimitCheck check(isolate()); + if (check.HasOverflowed()) { + fail("Stack overflow"); + return; + } + if (that->info()->been_analyzed || that->info()->being_analyzed) return; + that->info()->being_analyzed = true; + that->Accept(this); + that->info()->being_analyzed = false; + that->info()->been_analyzed = true; + } + + bool has_failed() { return error_message_ != nullptr; } + const char* error_message() { + DCHECK(error_message_ != nullptr); + return error_message_; + } + void fail(const char* error_message) { error_message_ = error_message; } + + Isolate* isolate() const { return isolate_; } + + void VisitEnd(EndNode* that) override { + // nothing to do + } + +// Used to call the given static function on each propagator / variadic template +// argument. +#define STATIC_FOR_EACH(expr) \ + do { \ + int dummy[] = {((expr), 0)...}; \ + USE(dummy); \ + } while (false) + + void VisitText(TextNode* that) override { + that->MakeCaseIndependent(isolate(), is_one_byte_); + EnsureAnalyzed(that->on_success()); + if (has_failed()) return; + that->CalculateOffsets(); + STATIC_FOR_EACH(Propagators::VisitText(that)); + } + + void VisitAction(ActionNode* that) override { + EnsureAnalyzed(that->on_success()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitAction(that)); + } + + void VisitChoice(ChoiceNode* that) override { + for (int i = 0; i < that->alternatives()->length(); i++) { + EnsureAnalyzed(that->alternatives()->at(i).node()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitChoice(that, i)); + } + } + + void VisitLoopChoice(LoopChoiceNode* that) override { + DCHECK_EQ(that->alternatives()->length(), 2); // Just loop and continue. + + // First propagate all information from the continuation node. + EnsureAnalyzed(that->continue_node()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitLoopChoiceContinueNode(that)); + + // Check the loop last since it may need the value of this node + // to get a correct result. + EnsureAnalyzed(that->loop_node()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitLoopChoiceLoopNode(that)); + } + + void VisitNegativeLookaroundChoice( + NegativeLookaroundChoiceNode* that) override { + DCHECK_EQ(that->alternatives()->length(), 2); // Lookaround and continue. + + EnsureAnalyzed(that->lookaround_node()); + if (has_failed()) return; + STATIC_FOR_EACH( + Propagators::VisitNegativeLookaroundChoiceLookaroundNode(that)); + + EnsureAnalyzed(that->continue_node()); + if (has_failed()) return; + STATIC_FOR_EACH( + Propagators::VisitNegativeLookaroundChoiceContinueNode(that)); + } + + void VisitBackReference(BackReferenceNode* that) override { + EnsureAnalyzed(that->on_success()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitBackReference(that)); + } + + void VisitAssertion(AssertionNode* that) override { + EnsureAnalyzed(that->on_success()); + if (has_failed()) return; + STATIC_FOR_EACH(Propagators::VisitAssertion(that)); + } + +#undef STATIC_FOR_EACH + + private: + Isolate* isolate_; + bool is_one_byte_; + const char* error_message_; + + DISALLOW_IMPLICIT_CONSTRUCTORS(Analysis); +}; + +const char* AnalyzeRegExp(Isolate* isolate, bool is_one_byte, + RegExpNode* node) { + Analysis<AssertionPropagator, EatsAtLeastPropagator> analysis(isolate, + is_one_byte); + DCHECK_EQ(node->info()->been_analyzed, false); + analysis.EnsureAnalyzed(node); + DCHECK_IMPLIES(analysis.has_failed(), analysis.error_message() != nullptr); + return analysis.has_failed() ? analysis.error_message() : nullptr; +} + +void BackReferenceNode::FillInBMInfo(Isolate* isolate, int offset, int budget, + BoyerMooreLookahead* bm, + bool not_at_start) { + // Working out the set of characters that a backreference can match is too + // hard, so we just say that any character can match. + bm->SetRest(offset); + SaveBMInfo(bm, not_at_start, offset); +} + +STATIC_ASSERT(BoyerMoorePositionInfo::kMapSize == + RegExpMacroAssembler::kTableSize); + +void ChoiceNode::FillInBMInfo(Isolate* isolate, int offset, int budget, + BoyerMooreLookahead* bm, bool not_at_start) { + ZoneList<GuardedAlternative>* alts = alternatives(); + budget = (budget - 1) / alts->length(); + for (int i = 0; i < alts->length(); i++) { + GuardedAlternative& alt = alts->at(i); + if (alt.guards() != nullptr && alt.guards()->length() != 0) { + bm->SetRest(offset); // Give up trying to fill in info. + SaveBMInfo(bm, not_at_start, offset); + return; + } + alt.node()->FillInBMInfo(isolate, offset, budget, bm, not_at_start); + } + SaveBMInfo(bm, not_at_start, offset); +} + +void TextNode::FillInBMInfo(Isolate* isolate, int initial_offset, int budget, + BoyerMooreLookahead* bm, bool not_at_start) { + if (initial_offset >= bm->length()) return; + int offset = initial_offset; + int max_char = bm->max_char(); + for (int i = 0; i < elements()->length(); i++) { + if (offset >= bm->length()) { + if (initial_offset == 0) set_bm_info(not_at_start, bm); + return; + } + TextElement text = elements()->at(i); + if (text.text_type() == TextElement::ATOM) { + RegExpAtom* atom = text.atom(); + for (int j = 0; j < atom->length(); j++, offset++) { + if (offset >= bm->length()) { + if (initial_offset == 0) set_bm_info(not_at_start, bm); + return; + } + uc16 character = atom->data()[j]; + if (IgnoreCase(atom->flags())) { + unibrow::uchar chars[4]; + int length = GetCaseIndependentLetters( + isolate, character, bm->max_char() == String::kMaxOneByteCharCode, + chars, 4); + for (int j = 0; j < length; j++) { + bm->Set(offset, chars[j]); + } + } else { + if (character <= max_char) bm->Set(offset, character); + } + } + } else { + DCHECK_EQ(TextElement::CHAR_CLASS, text.text_type()); + RegExpCharacterClass* char_class = text.char_class(); + ZoneList<CharacterRange>* ranges = char_class->ranges(zone()); + if (char_class->is_negated()) { + bm->SetAll(offset); + } else { + for (int k = 0; k < ranges->length(); k++) { + CharacterRange& range = ranges->at(k); + if (range.from() > max_char) continue; + int to = Min(max_char, static_cast<int>(range.to())); + bm->SetInterval(offset, Interval(range.from(), to)); + } + } + offset++; + } + } + if (offset >= bm->length()) { + if (initial_offset == 0) set_bm_info(not_at_start, bm); + return; + } + on_success()->FillInBMInfo(isolate, offset, budget - 1, bm, + true); // Not at start after a text node. + if (initial_offset == 0) set_bm_info(not_at_start, bm); +} + +// static +RegExpNode* RegExpCompiler::OptionallyStepBackToLeadSurrogate( + RegExpCompiler* compiler, RegExpNode* on_success, JSRegExp::Flags flags) { + DCHECK(!compiler->read_backward()); + Zone* zone = compiler->zone(); + ZoneList<CharacterRange>* lead_surrogates = CharacterRange::List( + zone, CharacterRange::Range(kLeadSurrogateStart, kLeadSurrogateEnd)); + ZoneList<CharacterRange>* trail_surrogates = CharacterRange::List( + zone, CharacterRange::Range(kTrailSurrogateStart, kTrailSurrogateEnd)); + + ChoiceNode* optional_step_back = new (zone) ChoiceNode(2, zone); + + int stack_register = compiler->UnicodeLookaroundStackRegister(); + int position_register = compiler->UnicodeLookaroundPositionRegister(); + RegExpNode* step_back = TextNode::CreateForCharacterRanges( + zone, lead_surrogates, true, on_success, flags); + RegExpLookaround::Builder builder(true, step_back, stack_register, + position_register); + RegExpNode* match_trail = TextNode::CreateForCharacterRanges( + zone, trail_surrogates, false, builder.on_match_success(), flags); + + optional_step_back->AddAlternative( + GuardedAlternative(builder.ForMatch(match_trail))); + optional_step_back->AddAlternative(GuardedAlternative(on_success)); + + return optional_step_back; +} + +} // namespace internal +} // namespace v8 |