summaryrefslogtreecommitdiff
path: root/js/src/jit/Safepoints.cpp
blob: 9446861a0b747ba4ea3962608f43c281b5ea988b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "jit/Safepoints.h"

#include "mozilla/MathAlgorithms.h"
#include "mozilla/SizePrintfMacros.h"

#include "jit/BitSet.h"
#include "jit/JitSpewer.h"
#include "jit/LIR.h"

using namespace js;
using namespace jit;

using mozilla::FloorLog2;

SafepointWriter::SafepointWriter(uint32_t slotCount, uint32_t argumentCount)
  : frameSlots_((slotCount / sizeof(intptr_t)) + 1), // Stack slot counts are inclusive.
    argumentSlots_(argumentCount / sizeof(intptr_t))
{ }

bool
SafepointWriter::init(TempAllocator& alloc)
{
    return frameSlots_.init(alloc) && argumentSlots_.init(alloc);
}

uint32_t
SafepointWriter::startEntry()
{
    JitSpew(JitSpew_Safepoints, "Encoding safepoint (position %" PRIuSIZE "):", stream_.length());
    return uint32_t(stream_.length());
}

void
SafepointWriter::writeOsiCallPointOffset(uint32_t osiCallPointOffset)
{
    stream_.writeUnsigned(osiCallPointOffset);
}

static void
WriteRegisterMask(CompactBufferWriter& stream, uint32_t bits)
{
    if (sizeof(PackedRegisterMask) == 1)
        stream.writeByte(bits);
    else
        stream.writeUnsigned(bits);
}

static int32_t
ReadRegisterMask(CompactBufferReader& stream)
{
    if (sizeof(PackedRegisterMask) == 1)
        return stream.readByte();
    return stream.readUnsigned();
}

static void
WriteFloatRegisterMask(CompactBufferWriter& stream, uint64_t bits)
{
    if (sizeof(FloatRegisters::SetType) == 1) {
        stream.writeByte(bits);
    } else if (sizeof(FloatRegisters::SetType) == 4) {
        stream.writeUnsigned(bits);
    } else {
        MOZ_ASSERT(sizeof(FloatRegisters::SetType) == 8);
        stream.writeUnsigned(bits & 0xffffffff);
        stream.writeUnsigned(bits >> 32);
    }
}

static int64_t
ReadFloatRegisterMask(CompactBufferReader& stream)
{
    if (sizeof(FloatRegisters::SetType) == 1)
        return stream.readByte();
    if (sizeof(FloatRegisters::SetType) <= 4)
        return stream.readUnsigned();
    MOZ_ASSERT(sizeof(FloatRegisters::SetType) == 8);
    uint64_t ret = stream.readUnsigned();
    ret |= uint64_t(stream.readUnsigned()) << 32;
    return ret;
}

void
SafepointWriter::writeGcRegs(LSafepoint* safepoint)
{
    LiveGeneralRegisterSet gc(safepoint->gcRegs());
    LiveGeneralRegisterSet spilledGpr(safepoint->liveRegs().gprs());
    LiveFloatRegisterSet spilledFloat(safepoint->liveRegs().fpus());
    LiveGeneralRegisterSet slots(safepoint->slotsOrElementsRegs());
    LiveGeneralRegisterSet valueRegs;

    WriteRegisterMask(stream_, spilledGpr.bits());
    if (!spilledGpr.empty()) {
        WriteRegisterMask(stream_, gc.bits());
        WriteRegisterMask(stream_, slots.bits());

#ifdef JS_PUNBOX64
        valueRegs = safepoint->valueRegs();
        WriteRegisterMask(stream_, valueRegs.bits());
#endif
    }

    // GC registers are a subset of the spilled registers.
    MOZ_ASSERT((valueRegs.bits() & ~spilledGpr.bits()) == 0);
    MOZ_ASSERT((gc.bits() & ~spilledGpr.bits()) == 0);

    WriteFloatRegisterMask(stream_, spilledFloat.bits());

#ifdef JS_JITSPEW
    if (JitSpewEnabled(JitSpew_Safepoints)) {
        for (GeneralRegisterForwardIterator iter(spilledGpr); iter.more(); ++iter) {
            const char* type = gc.has(*iter)
                               ? "gc"
                               : slots.has(*iter)
                                 ? "slots"
                                 : valueRegs.has(*iter)
                                   ? "value"
                                   : "any";
            JitSpew(JitSpew_Safepoints, "    %s reg: %s", type, (*iter).name());
        }
        for (FloatRegisterForwardIterator iter(spilledFloat); iter.more(); ++iter)
            JitSpew(JitSpew_Safepoints, "    float reg: %s", (*iter).name());
    }
#endif
}

static void
WriteBitset(const BitSet& set, CompactBufferWriter& stream)
{
    size_t count = set.rawLength();
    const uint32_t* words = set.raw();
    for (size_t i = 0; i < count; i++)
        stream.writeUnsigned(words[i]);
}

static void
MapSlotsToBitset(BitSet& stackSet, BitSet& argumentSet,
                 CompactBufferWriter& stream, const LSafepoint::SlotList& slots)
{
    stackSet.clear();
    argumentSet.clear();

    for (uint32_t i = 0; i < slots.length(); i++) {
        // Slots are represented at a distance from |fp|. We divide by the
        // pointer size, since we only care about pointer-sized/aligned slots
        // here.
        MOZ_ASSERT(slots[i].slot % sizeof(intptr_t) == 0);
        size_t index = slots[i].slot / sizeof(intptr_t);
        (slots[i].stack ? stackSet : argumentSet).insert(index);
    }

    WriteBitset(stackSet, stream);
    WriteBitset(argumentSet, stream);
}

void
SafepointWriter::writeGcSlots(LSafepoint* safepoint)
{
    LSafepoint::SlotList& slots = safepoint->gcSlots();

#ifdef JS_JITSPEW
    for (uint32_t i = 0; i < slots.length(); i++)
        JitSpew(JitSpew_Safepoints, "    gc slot: %u", slots[i].slot);
#endif

    MapSlotsToBitset(frameSlots_, argumentSlots_, stream_, slots);
}

void
SafepointWriter::writeSlotsOrElementsSlots(LSafepoint* safepoint)
{
    LSafepoint::SlotList& slots = safepoint->slotsOrElementsSlots();

    stream_.writeUnsigned(slots.length());

    for (uint32_t i = 0; i < slots.length(); i++) {
        if (!slots[i].stack)
            MOZ_CRASH();
#ifdef JS_JITSPEW
        JitSpew(JitSpew_Safepoints, "    slots/elements slot: %d", slots[i].slot);
#endif
        stream_.writeUnsigned(slots[i].slot);
    }
}

void
SafepointWriter::writeValueSlots(LSafepoint* safepoint)
{
    LSafepoint::SlotList& slots = safepoint->valueSlots();

#ifdef JS_JITSPEW
    for (uint32_t i = 0; i < slots.length(); i++)
        JitSpew(JitSpew_Safepoints, "    gc value: %u", slots[i].slot);
#endif

    MapSlotsToBitset(frameSlots_, argumentSlots_, stream_, slots);
}

#if defined(JS_JITSPEW) && defined(JS_NUNBOX32)
static void
DumpNunboxPart(const LAllocation& a)
{
    Fprinter& out = JitSpewPrinter();
    if (a.isStackSlot()) {
        out.printf("stack %d", a.toStackSlot()->slot());
    } else if (a.isArgument()) {
        out.printf("arg %d", a.toArgument()->index());
    } else {
        out.printf("reg %s", a.toGeneralReg()->reg().name());
    }
}
#endif // DEBUG

// Nunbox part encoding:
//
// Reg = 000
// Stack = 001
// Arg = 010
//
// [vwu] nentries:
//    uint16_t:  tttp ppXX XXXY YYYY
//
//     If ttt = Reg, type is reg XXXXX
//     If ppp = Reg, payload is reg YYYYY
//
//     If ttt != Reg, type is:
//          XXXXX if not 11111, otherwise followed by [vwu]
//     If ppp != Reg, payload is:
//          YYYYY if not 11111, otherwise followed by [vwu]
//
enum NunboxPartKind {
    Part_Reg,
    Part_Stack,
    Part_Arg
};

static const uint32_t PART_KIND_BITS = 3;
static const uint32_t PART_KIND_MASK = (1 << PART_KIND_BITS) - 1;
static const uint32_t PART_INFO_BITS = 5;
static const uint32_t PART_INFO_MASK = (1 << PART_INFO_BITS) - 1;

static const uint32_t MAX_INFO_VALUE = (1 << PART_INFO_BITS) - 1;
static const uint32_t TYPE_KIND_SHIFT = 16 - PART_KIND_BITS;
static const uint32_t PAYLOAD_KIND_SHIFT = TYPE_KIND_SHIFT - PART_KIND_BITS;
static const uint32_t TYPE_INFO_SHIFT = PAYLOAD_KIND_SHIFT - PART_INFO_BITS;
static const uint32_t PAYLOAD_INFO_SHIFT = TYPE_INFO_SHIFT - PART_INFO_BITS;

JS_STATIC_ASSERT(PAYLOAD_INFO_SHIFT == 0);

#ifdef JS_NUNBOX32
static inline NunboxPartKind
AllocationToPartKind(const LAllocation& a)
{
    if (a.isRegister())
        return Part_Reg;
    if (a.isStackSlot())
        return Part_Stack;
    MOZ_ASSERT(a.isArgument());
    return Part_Arg;
}

// gcc 4.5 doesn't actually inline CanEncodeInfoInHeader when only
// using the "inline" keyword, and miscompiles the function as well
// when doing block reordering with branch prediction information.
// See bug 799295 comment 71.
static MOZ_ALWAYS_INLINE bool
CanEncodeInfoInHeader(const LAllocation& a, uint32_t* out)
{
    if (a.isGeneralReg()) {
        *out = a.toGeneralReg()->reg().code();
        return true;
    }

    if (a.isStackSlot())
        *out = a.toStackSlot()->slot();
    else
        *out = a.toArgument()->index();

    return *out < MAX_INFO_VALUE;
}

void
SafepointWriter::writeNunboxParts(LSafepoint* safepoint)
{
    LSafepoint::NunboxList& entries = safepoint->nunboxParts();

# ifdef JS_JITSPEW
    if (JitSpewEnabled(JitSpew_Safepoints)) {
        for (uint32_t i = 0; i < entries.length(); i++) {
            SafepointNunboxEntry& entry = entries[i];
            if (entry.type.isUse() || entry.payload.isUse())
                continue;
            JitSpewHeader(JitSpew_Safepoints);
            Fprinter& out = JitSpewPrinter();
            out.printf("    nunbox (type in ");
            DumpNunboxPart(entry.type);
            out.printf(", payload in ");
            DumpNunboxPart(entry.payload);
            out.printf(")\n");
        }
    }
# endif

    // Safepoints are permitted to have partially filled in entries for nunboxes,
    // provided that only the type is live and not the payload. Omit these from
    // the written safepoint.

    size_t pos = stream_.length();
    stream_.writeUnsigned(entries.length());

    size_t count = 0;
    for (size_t i = 0; i < entries.length(); i++) {
        SafepointNunboxEntry& entry = entries[i];

        if (entry.payload.isUse()) {
            // No allocation associated with the payload.
            continue;
        }

        if (entry.type.isUse()) {
            // No allocation associated with the type. Look for another
            // safepoint entry with an allocation for the type.
            entry.type = safepoint->findTypeAllocation(entry.typeVreg);
            if (entry.type.isUse())
                continue;
        }

        count++;

        uint16_t header = 0;

        header |= (AllocationToPartKind(entry.type) << TYPE_KIND_SHIFT);
        header |= (AllocationToPartKind(entry.payload) << PAYLOAD_KIND_SHIFT);

        uint32_t typeVal;
        bool typeExtra = !CanEncodeInfoInHeader(entry.type, &typeVal);
        if (!typeExtra)
            header |= (typeVal << TYPE_INFO_SHIFT);
        else
            header |= (MAX_INFO_VALUE << TYPE_INFO_SHIFT);

        uint32_t payloadVal;
        bool payloadExtra = !CanEncodeInfoInHeader(entry.payload, &payloadVal);
        if (!payloadExtra)
            header |= (payloadVal << PAYLOAD_INFO_SHIFT);
        else
            header |= (MAX_INFO_VALUE << PAYLOAD_INFO_SHIFT);

        stream_.writeFixedUint16_t(header);
        if (typeExtra)
            stream_.writeUnsigned(typeVal);
        if (payloadExtra)
            stream_.writeUnsigned(payloadVal);
    }

    // Update the stream with the actual number of safepoint entries written.
    stream_.writeUnsignedAt(pos, count, entries.length());
}
#endif

void
SafepointWriter::encode(LSafepoint* safepoint)
{
    uint32_t safepointOffset = startEntry();

    MOZ_ASSERT(safepoint->osiCallPointOffset());

    writeOsiCallPointOffset(safepoint->osiCallPointOffset());
    writeGcRegs(safepoint);
    writeGcSlots(safepoint);
    writeValueSlots(safepoint);

#ifdef JS_NUNBOX32
    writeNunboxParts(safepoint);
#endif

    writeSlotsOrElementsSlots(safepoint);

    endEntry();
    safepoint->setOffset(safepointOffset);
}

void
SafepointWriter::endEntry()
{
    JitSpew(JitSpew_Safepoints, "    -- entry ended at %d", uint32_t(stream_.length()));
}

SafepointReader::SafepointReader(IonScript* script, const SafepointIndex* si)
  : stream_(script->safepoints() + si->safepointOffset(),
            script->safepoints() + script->safepointsSize()),
    frameSlots_((script->frameSlots() / sizeof(intptr_t)) + 1), // Stack slot counts are inclusive.
    argumentSlots_(script->argumentSlots() / sizeof(intptr_t))
{
    osiCallPointOffset_ = stream_.readUnsigned();

    // gcSpills is a subset of allGprSpills.
    allGprSpills_ = GeneralRegisterSet(ReadRegisterMask(stream_));
    if (allGprSpills_.empty()) {
        gcSpills_ = allGprSpills_;
        valueSpills_ = allGprSpills_;
        slotsOrElementsSpills_ = allGprSpills_;
    } else {
        gcSpills_ = GeneralRegisterSet(ReadRegisterMask(stream_));
        slotsOrElementsSpills_ = GeneralRegisterSet(ReadRegisterMask(stream_));
#ifdef JS_PUNBOX64
        valueSpills_ = GeneralRegisterSet(ReadRegisterMask(stream_));
#endif
    }
    allFloatSpills_ = FloatRegisterSet(ReadFloatRegisterMask(stream_));

    advanceFromGcRegs();
}

uint32_t
SafepointReader::osiReturnPointOffset() const
{
    return osiCallPointOffset_ + Assembler::PatchWrite_NearCallSize();
}

CodeLocationLabel
SafepointReader::InvalidationPatchPoint(IonScript* script, const SafepointIndex* si)
{
    SafepointReader reader(script, si);

    return CodeLocationLabel(script->method(), CodeOffset(reader.osiCallPointOffset()));
}

void
SafepointReader::advanceFromGcRegs()
{
    currentSlotChunk_ = 0;
    nextSlotChunkNumber_ = 0;
    currentSlotsAreStack_ = true;
}

bool
SafepointReader::getSlotFromBitmap(SafepointSlotEntry* entry)
{
    while (currentSlotChunk_ == 0) {
        // Are there any more chunks to read?
        if (currentSlotsAreStack_) {
            if (nextSlotChunkNumber_ == BitSet::RawLengthForBits(frameSlots_)) {
                nextSlotChunkNumber_ = 0;
                currentSlotsAreStack_ = false;
                continue;
            }
        } else if (nextSlotChunkNumber_ == BitSet::RawLengthForBits(argumentSlots_)) {
            return false;
        }

        // Yes, read the next chunk.
        currentSlotChunk_ = stream_.readUnsigned();
        nextSlotChunkNumber_++;
    }

    // The current chunk still has bits in it, so get the next bit, then mask
    // it out of the slot chunk.
    uint32_t bit = FloorLog2(currentSlotChunk_);
    currentSlotChunk_ &= ~(1 << bit);

    // Return the slot, and re-scale it by the pointer size, reversing the
    // transformation in MapSlotsToBitset.
    entry->stack = currentSlotsAreStack_;
    entry->slot = (((nextSlotChunkNumber_ - 1) * BitSet::BitsPerWord) + bit) * sizeof(intptr_t);
    return true;
}

bool
SafepointReader::getGcSlot(SafepointSlotEntry* entry)
{
    if (getSlotFromBitmap(entry))
        return true;
    advanceFromGcSlots();
    return false;
}

void
SafepointReader::advanceFromGcSlots()
{
    // No, reset the counter.
    currentSlotChunk_ = 0;
    nextSlotChunkNumber_ = 0;
    currentSlotsAreStack_ = true;
}

bool
SafepointReader::getValueSlot(SafepointSlotEntry* entry)
{
    if (getSlotFromBitmap(entry))
        return true;
    advanceFromValueSlots();
    return false;
}

void
SafepointReader::advanceFromValueSlots()
{
#ifdef JS_NUNBOX32
    nunboxSlotsRemaining_ = stream_.readUnsigned();
#else
    nunboxSlotsRemaining_ = 0;
    advanceFromNunboxSlots();
#endif
}

static inline LAllocation
PartFromStream(CompactBufferReader& stream, NunboxPartKind kind, uint32_t info)
{
    if (kind == Part_Reg)
        return LGeneralReg(Register::FromCode(info));

    if (info == MAX_INFO_VALUE)
        info = stream.readUnsigned();

    if (kind == Part_Stack)
        return LStackSlot(info);

    MOZ_ASSERT(kind == Part_Arg);
    return LArgument(info);
}

bool
SafepointReader::getNunboxSlot(LAllocation* type, LAllocation* payload)
{
    if (!nunboxSlotsRemaining_--) {
        advanceFromNunboxSlots();
        return false;
    }

    uint16_t header = stream_.readFixedUint16_t();
    NunboxPartKind typeKind = (NunboxPartKind)((header >> TYPE_KIND_SHIFT) & PART_KIND_MASK);
    NunboxPartKind payloadKind = (NunboxPartKind)((header >> PAYLOAD_KIND_SHIFT) & PART_KIND_MASK);
    uint32_t typeInfo = (header >> TYPE_INFO_SHIFT) & PART_INFO_MASK;
    uint32_t payloadInfo = (header >> PAYLOAD_INFO_SHIFT) & PART_INFO_MASK;

    *type = PartFromStream(stream_, typeKind, typeInfo);
    *payload = PartFromStream(stream_, payloadKind, payloadInfo);
    return true;
}

void
SafepointReader::advanceFromNunboxSlots()
{
    slotsOrElementsSlotsRemaining_ = stream_.readUnsigned();
}

bool
SafepointReader::getSlotsOrElementsSlot(SafepointSlotEntry* entry)
{
    if (!slotsOrElementsSlotsRemaining_--)
        return false;
    entry->stack = true;
    entry->slot = stream_.readUnsigned();
    return true;
}