src/third_party/mozjs/js/src/jit/shared/CodeGenerator-shared.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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 "mozilla/DebugOnly.h"

#include "CodeGenerator-shared.h"
#include "jit/MIRGenerator.h"
#include "jit/IonFrames-inl.h"
#include "jit/MIR.h"
#include "CodeGenerator-shared-inl.h"
#include "jit/IonSpewer.h"
#include "jit/IonMacroAssembler.h"
#include "jit/ParallelFunctions.h"
#include "builtin/ParallelArray.h"

using namespace js;
using namespace js::jit;

using mozilla::DebugOnly;

namespace js {
namespace jit {

MacroAssembler &
CodeGeneratorShared::ensureMasm(MacroAssembler *masmArg)
{
    if (masmArg)
        return *masmArg;
    maybeMasm_.construct();
    return maybeMasm_.ref();
}

CodeGeneratorShared::CodeGeneratorShared(MIRGenerator *gen, LIRGraph *graph, MacroAssembler *masmArg)
  : oolIns(NULL),
    maybeMasm_(),
    masm(ensureMasm(masmArg)),
    gen(gen),
    graph(*graph),
    current(NULL),
    deoptTable_(NULL),
#ifdef DEBUG
    pushedArgs_(0),
#endif
    lastOsiPointOffset_(0),
    sps_(&gen->compartment->rt->spsProfiler, &lastPC_),
    osrEntryOffset_(0),
    skipArgCheckEntryOffset_(0),
    frameDepth_(graph->localSlotCount() * sizeof(STACK_SLOT_SIZE) +
                graph->argumentSlotCount() * sizeof(Value))
{
    if (!gen->compilingAsmJS())
        masm.setInstrumentation(&sps_);

    // Since asm.js uses the system ABI which does not necessarily use a
    // regular array where all slots are sizeof(Value), it maintains the max
    // argument stack depth separately.
    if (gen->compilingAsmJS()) {
        JS_ASSERT(graph->argumentSlotCount() == 0);
        frameDepth_ += gen->maxAsmJSStackArgBytes();

        // An MAsmJSCall does not align the stack pointer at calls sites but instead
        // relies on the a priori stack adjustment (in the prologue) on platforms
        // (like x64) which require the stack to be aligned.
#ifdef JS_CPU_ARM
        bool forceAlign = true;
#else
        bool forceAlign = false;
#endif
        if (gen->performsAsmJSCall() || forceAlign) {
            unsigned alignmentAtCall = AlignmentMidPrologue + frameDepth_;
            if (unsigned rem = alignmentAtCall % StackAlignment)
                frameDepth_ += StackAlignment - rem;
        }

        // FrameSizeClass is only used for bailing, which cannot happen in
        // asm.js code.
        frameClass_ = FrameSizeClass::None();
    } else {
        frameClass_ = FrameSizeClass::FromDepth(frameDepth_);
    }
}

bool
CodeGeneratorShared::generateOutOfLineCode()
{
    for (size_t i = 0; i < outOfLineCode_.length(); i++) {
        if (!gen->temp().ensureBallast())
            return false;
        masm.setFramePushed(outOfLineCode_[i]->framePushed());
        lastPC_ = outOfLineCode_[i]->pc();
        sps_.setPushed(outOfLineCode_[i]->script());
        outOfLineCode_[i]->bind(&masm);

        oolIns = outOfLineCode_[i];
        if (!outOfLineCode_[i]->generate(this))
            return false;
    }
    oolIns = NULL;

    return true;
}

bool
CodeGeneratorShared::addOutOfLineCode(OutOfLineCode *code)
{
    code->setFramePushed(masm.framePushed());
    // If an OOL instruction adds another OOL instruction, then use the original
    // instruction's script/pc instead of the basic block's that we're on
    // because they're probably not relevant any more.
    if (oolIns)
        code->setSource(oolIns->script(), oolIns->pc());
    else
        code->setSource(current ? current->mir()->info().script() : NULL, lastPC_);
    return outOfLineCode_.append(code);
}

// see OffsetOfFrameSlot
static inline int32_t
ToStackIndex(LAllocation *a)
{
    if (a->isStackSlot()) {
        JS_ASSERT(a->toStackSlot()->slot() >= 1);
        return a->toStackSlot()->slot();
    }
    JS_ASSERT(-int32_t(sizeof(IonJSFrameLayout)) <= a->toArgument()->index());
    return -(sizeof(IonJSFrameLayout) + a->toArgument()->index());
}

bool
CodeGeneratorShared::encodeSlots(LSnapshot *snapshot, MResumePoint *resumePoint,
                                 uint32_t *startIndex)
{
    IonSpew(IonSpew_Codegen, "Encoding %u of resume point %p's operands starting from %u",
            resumePoint->numOperands(), (void *) resumePoint, *startIndex);
    for (uint32_t slotno = 0; slotno < resumePoint->numOperands(); slotno++) {
        uint32_t i = slotno + *startIndex;
        MDefinition *mir = resumePoint->getOperand(slotno);

        if (mir->isPassArg())
            mir = mir->toPassArg()->getArgument();
        JS_ASSERT(!mir->isPassArg());

        MIRType type = mir->isUnused()
                       ? MIRType_Undefined
                       : mir->type();

        switch (type) {
          case MIRType_Undefined:
            snapshots_.addUndefinedSlot();
            break;
          case MIRType_Null:
            snapshots_.addNullSlot();
            break;
          case MIRType_Int32:
          case MIRType_String:
          case MIRType_Object:
          case MIRType_Boolean:
          case MIRType_Double:
          {
            LAllocation *payload = snapshot->payloadOfSlot(i);
            JSValueType type = ValueTypeFromMIRType(mir->type());
            if (payload->isMemory()) {
                snapshots_.addSlot(type, ToStackIndex(payload));
            } else if (payload->isGeneralReg()) {
                snapshots_.addSlot(type, ToRegister(payload));
            } else if (payload->isFloatReg()) {
                snapshots_.addSlot(ToFloatRegister(payload));
            } else {
                MConstant *constant = mir->toConstant();
                const Value &v = constant->value();

                // Don't bother with the constant pool for smallish integers.
                if (v.isInt32() && v.toInt32() >= -32 && v.toInt32() <= 32) {
                    snapshots_.addInt32Slot(v.toInt32());
                } else {
                    uint32_t index;
                    if (!graph.addConstantToPool(constant->value(), &index))
                        return false;
                    snapshots_.addConstantPoolSlot(index);
                }
            }
            break;
          }
          case MIRType_Magic:
          {
            uint32_t index;
            if (!graph.addConstantToPool(MagicValue(JS_OPTIMIZED_ARGUMENTS), &index))
                return false;
            snapshots_.addConstantPoolSlot(index);
            break;
          }
          default:
          {
            JS_ASSERT(mir->type() == MIRType_Value);
            LAllocation *payload = snapshot->payloadOfSlot(i);
#ifdef JS_NUNBOX32
            LAllocation *type = snapshot->typeOfSlot(i);
            if (type->isRegister()) {
                if (payload->isRegister())
                    snapshots_.addSlot(ToRegister(type), ToRegister(payload));
                else
                    snapshots_.addSlot(ToRegister(type), ToStackIndex(payload));
            } else {
                if (payload->isRegister())
                    snapshots_.addSlot(ToStackIndex(type), ToRegister(payload));
                else
                    snapshots_.addSlot(ToStackIndex(type), ToStackIndex(payload));
            }
#elif JS_PUNBOX64
            if (payload->isRegister())
                snapshots_.addSlot(ToRegister(payload));
            else
                snapshots_.addSlot(ToStackIndex(payload));
#endif
            break;
          }
      }
    }

    *startIndex += resumePoint->numOperands();
    return true;
}

bool
CodeGeneratorShared::encode(LSnapshot *snapshot)
{
    if (snapshot->snapshotOffset() != INVALID_SNAPSHOT_OFFSET)
        return true;

    uint32_t frameCount = snapshot->mir()->frameCount();

    IonSpew(IonSpew_Snapshots, "Encoding LSnapshot %p (frameCount %u)",
            (void *)snapshot, frameCount);

    MResumePoint::Mode mode = snapshot->mir()->mode();
    JS_ASSERT(mode != MResumePoint::Outer);
    bool resumeAfter = (mode == MResumePoint::ResumeAfter);

    SnapshotOffset offset = snapshots_.startSnapshot(frameCount, snapshot->bailoutKind(),
                                                     resumeAfter);

    FlattenedMResumePointIter mirOperandIter(snapshot->mir());
    if (!mirOperandIter.init())
        return false;

    uint32_t startIndex = 0;
    for (MResumePoint **it = mirOperandIter.begin(), **end = mirOperandIter.end();
         it != end;
         ++it)
    {
        MResumePoint *mir = *it;
        MBasicBlock *block = mir->block();
        JSFunction *fun = block->info().fun();
        JSScript *script = block->info().script();
        jsbytecode *pc = mir->pc();
        uint32_t exprStack = mir->stackDepth() - block->info().ninvoke();
        snapshots_.startFrame(fun, script, pc, exprStack);

        // Ensure that all snapshot which are encoded can safely be used for
        // bailouts.
        DebugOnly<jsbytecode *> bailPC = pc;
        if (mir->mode() == MResumePoint::ResumeAfter)
          bailPC = GetNextPc(pc);

#ifdef DEBUG
        if (GetIonContext()->cx) {
            uint32_t stackDepth = js_ReconstructStackDepth(GetIonContext()->cx, script, bailPC);
            if (JSOp(*bailPC) == JSOP_FUNCALL) {
                // For fun.call(this, ...); the reconstructStackDepth will
                // include the this. When inlining that is not included.
                // So the exprStackSlots will be one less.
                JS_ASSERT(stackDepth - exprStack <= 1);
            } else if (JSOp(*bailPC) != JSOP_FUNAPPLY) {
                // For fun.apply({}, arguments) the reconstructStackDepth will
                // have stackdepth 4, but it could be that we inlined the
                // funapply. In that case exprStackSlots, will have the real
                // arguments in the slots and not be 4.
                JS_ASSERT(exprStack == stackDepth);
            }
        }
#endif

#ifdef TRACK_SNAPSHOTS
        LInstruction *ins = instruction();

        uint32_t pcOpcode = 0;
        uint32_t lirOpcode = 0;
        uint32_t lirId = 0;
        uint32_t mirOpcode = 0;
        uint32_t mirId = 0;

        if (ins) {
            lirOpcode = ins->op();
            lirId = ins->id();
            if (ins->mirRaw()) {
                mirOpcode = ins->mirRaw()->op();
                mirId = ins->mirRaw()->id();
                if (ins->mirRaw()->trackedPc())
                    pcOpcode = *ins->mirRaw()->trackedPc();
            }
        }
        snapshots_.trackFrame(pcOpcode, mirOpcode, mirId, lirOpcode, lirId);
#endif

        if (!encodeSlots(snapshot, mir, &startIndex))
            return false;
        snapshots_.endFrame();
    }

    snapshots_.endSnapshot();

    snapshot->setSnapshotOffset(offset);

    return !snapshots_.oom();
}

bool
CodeGeneratorShared::assignBailoutId(LSnapshot *snapshot)
{
    JS_ASSERT(snapshot->snapshotOffset() != INVALID_SNAPSHOT_OFFSET);

    // Can we not use bailout tables at all?
    if (!deoptTable_)
        return false;

    JS_ASSERT(frameClass_ != FrameSizeClass::None());

    if (snapshot->bailoutId() != INVALID_BAILOUT_ID)
        return true;

    // Is the bailout table full?
    if (bailouts_.length() >= BAILOUT_TABLE_SIZE)
        return false;

    unsigned bailoutId = bailouts_.length();
    snapshot->setBailoutId(bailoutId);
    IonSpew(IonSpew_Snapshots, "Assigned snapshot bailout id %u", bailoutId);
    return bailouts_.append(snapshot->snapshotOffset());
}

void
CodeGeneratorShared::encodeSafepoints()
{
    for (SafepointIndex *it = safepointIndices_.begin(), *end = safepointIndices_.end();
         it != end;
         ++it)
    {
        LSafepoint *safepoint = it->safepoint();

        if (!safepoint->encoded()) {
            safepoint->fixupOffset(&masm);
            safepoints_.encode(safepoint);
        }

        it->resolve();
    }
}

bool
CodeGeneratorShared::markSafepoint(LInstruction *ins)
{
    return markSafepointAt(masm.currentOffset(), ins);
}

bool
CodeGeneratorShared::markSafepointAt(uint32_t offset, LInstruction *ins)
{
    JS_ASSERT_IF(safepointIndices_.length(),
                 offset - safepointIndices_.back().displacement() >= sizeof(uint32_t));
    return safepointIndices_.append(SafepointIndex(offset, ins->safepoint()));
}

void
CodeGeneratorShared::ensureOsiSpace()
{
    // For a refresher, an invalidation point is of the form:
    // 1: call <target>
    // 2: ...
    // 3: <osipoint>
    //
    // The four bytes *before* instruction 2 are overwritten with an offset.
    // Callers must ensure that the instruction itself has enough bytes to
    // support this.
    //
    // The bytes *at* instruction 3 are overwritten with an invalidation jump.
    // jump. These bytes may be in a completely different IR sequence, but
    // represent the join point of the call out of the function.
    //
    // At points where we want to ensure that invalidation won't corrupt an
    // important instruction, we make sure to pad with nops.
    if (masm.currentOffset() - lastOsiPointOffset_ < Assembler::patchWrite_NearCallSize()) {
        int32_t paddingSize = Assembler::patchWrite_NearCallSize();
        paddingSize -= masm.currentOffset() - lastOsiPointOffset_;
        for (int32_t i = 0; i < paddingSize; ++i)
            masm.nop();
    }
    JS_ASSERT(masm.currentOffset() - lastOsiPointOffset_ >= Assembler::patchWrite_NearCallSize());
    lastOsiPointOffset_ = masm.currentOffset();
}

bool
CodeGeneratorShared::markOsiPoint(LOsiPoint *ins, uint32_t *callPointOffset)
{
    if (!encode(ins->snapshot()))
        return false;

    ensureOsiSpace();

    *callPointOffset = masm.currentOffset();
    SnapshotOffset so = ins->snapshot()->snapshotOffset();
    return osiIndices_.append(OsiIndex(*callPointOffset, so));
}

// Before doing any call to Cpp, you should ensure that volatile
// registers are evicted by the register allocator.
bool
CodeGeneratorShared::callVM(const VMFunction &fun, LInstruction *ins, const Register *dynStack)
{
    // Different execution modes have different sets of VM functions.
    JS_ASSERT(fun.executionMode == gen->info().executionMode());

#ifdef DEBUG
    if (ins->mirRaw()) {
        JS_ASSERT(ins->mirRaw()->isInstruction());
        MInstruction *mir = ins->mirRaw()->toInstruction();
        JS_ASSERT_IF(mir->isEffectful(), mir->resumePoint());
    }
#endif

    // Stack is:
    //    ... frame ...
    //    [args]
#ifdef DEBUG
    JS_ASSERT(pushedArgs_ == fun.explicitArgs);
    pushedArgs_ = 0;
#endif

    // Get the wrapper of the VM function.
    IonCompartment *ion = GetIonContext()->compartment->ionCompartment();
    IonCode *wrapper = ion->getVMWrapper(fun);
    if (!wrapper)
        return false;

    // Call the wrapper function.  The wrapper is in charge to unwind the stack
    // when returning from the call.  Failures are handled with exceptions based
    // on the return value of the C functions.  To guard the outcome of the
    // returned value, use another LIR instruction.
    uint32_t callOffset;
    if (dynStack)
        callOffset = masm.callWithExitFrame(wrapper, *dynStack);
    else
        callOffset = masm.callWithExitFrame(wrapper);

    if (!markSafepointAt(callOffset, ins))
        return false;

    // Remove rest of the frame left on the stack. We remove the return address
    // which is implicitly poped when returning.
    int framePop = sizeof(IonExitFrameLayout) - sizeof(void*);

    // Pop arguments from framePushed.
    masm.implicitPop(fun.explicitStackSlots() * sizeof(void *) + framePop);
    // Stack is:
    //    ... frame ...
    return true;
}

class OutOfLineTruncateSlow : public OutOfLineCodeBase<CodeGeneratorShared>
{
    FloatRegister src_;
    Register dest_;

  public:
    OutOfLineTruncateSlow(FloatRegister src, Register dest)
      : src_(src), dest_(dest)
    { }

    bool accept(CodeGeneratorShared *codegen) {
        return codegen->visitOutOfLineTruncateSlow(this);
    }
    FloatRegister src() const {
        return src_;
    }
    Register dest() const {
        return dest_;
    }
};

bool
CodeGeneratorShared::emitTruncateDouble(const FloatRegister &src, const Register &dest)
{
    OutOfLineTruncateSlow *ool = new OutOfLineTruncateSlow(src, dest);
    if (!addOutOfLineCode(ool))
        return false;

    masm.branchTruncateDouble(src, dest, ool->entry());
    masm.bind(ool->rejoin());
    return true;
}

bool
CodeGeneratorShared::visitOutOfLineTruncateSlow(OutOfLineTruncateSlow *ool)
{
    FloatRegister src = ool->src();
    Register dest = ool->dest();

    saveVolatile(dest);

    masm.setupUnalignedABICall(1, dest);
    masm.passABIArg(src);
    masm.callWithABI(JS_FUNC_TO_DATA_PTR(void *, js::ToInt32));
    masm.storeCallResult(dest);

    restoreVolatile(dest);

    masm.jump(ool->rejoin());
    return true;
}

void
CodeGeneratorShared::emitPreBarrier(Register base, const LAllocation *index, MIRType type)
{
    if (index->isConstant()) {
        Address address(base, ToInt32(index) * sizeof(Value));
        masm.patchableCallPreBarrier(address, type);
    } else {
        BaseIndex address(base, ToRegister(index), TimesEight);
        masm.patchableCallPreBarrier(address, type);
    }
}

void
CodeGeneratorShared::emitPreBarrier(Address address, MIRType type)
{
    masm.patchableCallPreBarrier(address, type);
}

void
CodeGeneratorShared::dropArguments(unsigned argc)
{
    for (unsigned i = 0; i < argc; i++)
        pushedArgumentSlots_.popBack();
}

bool
CodeGeneratorShared::markArgumentSlots(LSafepoint *safepoint)
{
    for (size_t i = 0; i < pushedArgumentSlots_.length(); i++) {
        if (!safepoint->addValueSlot(pushedArgumentSlots_[i]))
            return false;
    }
    return true;
}

OutOfLineParallelAbort *
CodeGeneratorShared::oolParallelAbort(ParallelBailoutCause cause,
                                      MBasicBlock *basicBlock,
                                      jsbytecode *bytecode)
{
    OutOfLineParallelAbort *ool = new OutOfLineParallelAbort(cause, basicBlock, bytecode);
    if (!ool || !addOutOfLineCode(ool))
        return NULL;
    return ool;
}

OutOfLineParallelAbort *
CodeGeneratorShared::oolParallelAbort(ParallelBailoutCause cause,
                                      LInstruction *lir)
{
    MDefinition *mir = lir->mirRaw();
    MBasicBlock *block = mir->block();
    jsbytecode *pc = mir->trackedPc();
    if (!pc) {
        if (lir->snapshot())
            pc = lir->snapshot()->mir()->pc();
        else
            pc = block->pc();
    }
    return oolParallelAbort(cause, block, pc);
}

OutOfLinePropagateParallelAbort *
CodeGeneratorShared::oolPropagateParallelAbort(LInstruction *lir)
{
    OutOfLinePropagateParallelAbort *ool = new OutOfLinePropagateParallelAbort(lir);
    if (!ool || !addOutOfLineCode(ool))
        return NULL;
    return ool;
}

bool
OutOfLineParallelAbort::generate(CodeGeneratorShared *codegen)
{
    codegen->callTraceLIR(0xDEADBEEF, NULL, "ParallelBailout");
    return codegen->visitOutOfLineParallelAbort(this);
}

bool
OutOfLinePropagateParallelAbort::generate(CodeGeneratorShared *codegen)
{
    codegen->callTraceLIR(0xDEADBEEF, NULL, "ParallelBailout");
    return codegen->visitOutOfLinePropagateParallelAbort(this);
}

bool
CodeGeneratorShared::callTraceLIR(uint32_t blockIndex, LInstruction *lir,
                                    const char *bailoutName)
{
    JS_ASSERT_IF(!lir, bailoutName);

    uint32_t emi = (uint32_t) gen->info().executionMode();

    if (!IonSpewEnabled(IonSpew_Trace))
        return true;
    masm.PushRegsInMask(RegisterSet::All());

    RegisterSet regSet(RegisterSet::All());

    Register blockIndexReg = regSet.takeGeneral();
    Register lirIndexReg = regSet.takeGeneral();
    Register emiReg = regSet.takeGeneral();
    Register lirOpNameReg = regSet.takeGeneral();
    Register mirOpNameReg = regSet.takeGeneral();
    Register scriptReg = regSet.takeGeneral();
    Register pcReg = regSet.takeGeneral();

    // This first move is here so that when you scan the disassembly,
    // you can easily pick out where each instruction begins.  The
    // next few items indicate to you the Basic Block / LIR.
    masm.move32(Imm32(0xDEADBEEF), blockIndexReg);

    if (lir) {
        masm.move32(Imm32(blockIndex), blockIndexReg);
        masm.move32(Imm32(lir->id()), lirIndexReg);
        masm.move32(Imm32(emi), emiReg);
        masm.movePtr(ImmWord(lir->opName()), lirOpNameReg);
        if (MDefinition *mir = lir->mirRaw()) {
            masm.movePtr(ImmWord(mir->opName()), mirOpNameReg);
            masm.movePtr(ImmWord((void *)mir->block()->info().script()), scriptReg);
            masm.movePtr(ImmWord(mir->trackedPc()), pcReg);
        } else {
            masm.movePtr(ImmWord((void *)NULL), mirOpNameReg);
            masm.movePtr(ImmWord((void *)NULL), scriptReg);
            masm.movePtr(ImmWord((void *)NULL), pcReg);
        }
    } else {
        masm.move32(Imm32(0xDEADBEEF), blockIndexReg);
        masm.move32(Imm32(0xDEADBEEF), lirIndexReg);
        masm.move32(Imm32(emi), emiReg);
        masm.movePtr(ImmWord(bailoutName), lirOpNameReg);
        masm.movePtr(ImmWord(bailoutName), mirOpNameReg);
        masm.movePtr(ImmWord((void *)NULL), scriptReg);
        masm.movePtr(ImmWord((void *)NULL), pcReg);
    }

    masm.setupUnalignedABICall(7, CallTempReg4);
    masm.passABIArg(blockIndexReg);
    masm.passABIArg(lirIndexReg);
    masm.passABIArg(emiReg);
    masm.passABIArg(lirOpNameReg);
    masm.passABIArg(mirOpNameReg);
    masm.passABIArg(scriptReg);
    masm.passABIArg(pcReg);
    masm.callWithABI(JS_FUNC_TO_DATA_PTR(void *, TraceLIR));
    masm.PopRegsInMask(RegisterSet::All());
    return true;
}

} // namespace jit
} // namespace js