C++ MInstruction类代码示例

bool
FilterTypeSetPolicy::adjustInputs(TempAllocator &alloc, MInstruction *ins)
{
    MOZ_ASSERT(ins->numOperands() == 1);
    MIRType inputType = ins->getOperand(0)->type();
    MIRType outputType = ins->type();

    // Input and output type are already in accordance.
    if (inputType == outputType)
        return true;

    // Output is a value, box the input.
    if (outputType == MIRType_Value) {
        MOZ_ASSERT(inputType != MIRType_Value);
        ins->replaceOperand(0, BoxAt(alloc, ins, ins->getOperand(0)));
        return true;
    }

    // The outputType should be a subset of the inputType else we are in code
    // that has never executed yet. Bail to see the new type (if that hasn't
    // happened yet).
    if (inputType != MIRType_Value) {
        MBail *bail = MBail::New(alloc);
        ins->block()->insertBefore(ins, bail);
        bail->setDependency(ins->dependency());
        ins->setDependency(bail);
        ins->replaceOperand(0, BoxAt(alloc, ins, ins->getOperand(0)));
    }

    // We can't unbox a value to null/undefined/lazyargs. So keep output
    // also a value.
    // Note: Using setResultType shouldn't be done in TypePolicies,
    //       Here it is fine, since the type barrier has no uses.
    if (IsNullOrUndefined(outputType) || outputType == MIRType_MagicOptimizedArguments) {
        MOZ_ASSERT(!ins->hasDefUses());
        ins->setResultType(MIRType_Value);
        return true;
    }

    // Unbox / propagate the right type.
    MUnbox::Mode mode = MUnbox::Infallible;
    MInstruction *replace = MUnbox::New(alloc, ins->getOperand(0), ins->type(), mode);

    ins->block()->insertBefore(ins, replace);
    ins->replaceOperand(0, replace);
    if (!replace->typePolicy()->adjustInputs(alloc, replace))
        return false;

    // Carry over the dependency the MFilterTypeSet had.
    replace->setDependency(ins->dependency());

    return true;
}

bool
TypeBarrierPolicy::adjustInputs(TempAllocator &alloc, MInstruction *def)
{
    MTypeBarrier *ins = def->toTypeBarrier();
    MIRType inputType = ins->getOperand(0)->type();
    MIRType outputType = ins->type();

    // Input and output type are already in accordance.
    if (inputType == outputType)
        return true;

    // Output is a value, currently box the input.
    if (outputType == MIRType_Value) {
        // XXX: Possible optimization: decrease resultTypeSet to only include
        // the inputType. This will remove the need for boxing.
        MOZ_ASSERT(inputType != MIRType_Value);
        ins->replaceOperand(0, boxAt(alloc, ins, ins->getOperand(0)));
        return true;
    }

    // Box input if needed.
    if (inputType != MIRType_Value) {
        MOZ_ASSERT(ins->alwaysBails());
        ins->replaceOperand(0, boxAt(alloc, ins, ins->getOperand(0)));
    }

    // We can't unbox a value to null/undefined/lazyargs. So keep output
    // also a value.
    // Note: Using setResultType shouldn't be done in TypePolicies,
    //       Here it is fine, since the type barrier has no uses.
    if (IsNullOrUndefined(outputType) || outputType == MIRType_MagicOptimizedArguments) {
        MOZ_ASSERT(!ins->hasDefUses());
        ins->setResultType(MIRType_Value);
        return true;
    }

    // Unbox / propagate the right type.
    MUnbox::Mode mode = MUnbox::TypeBarrier;
    MInstruction *replace = MUnbox::New(alloc, ins->getOperand(0), ins->type(), mode);

    ins->block()->insertBefore(ins, replace);
    ins->replaceOperand(0, replace);
    if (!replace->typePolicy()->adjustInputs(alloc, replace))
        return false;

    // The TypeBarrier is equivalent to removing branches with unexpected
    // types.  The unexpected types would have changed Range Analysis
    // predictions.  As such, we need to prevent destructive optimizations.
    ins->block()->flagOperandsOfPrunedBranches(replace);

    return true;
}

MConstant*
MBasicBlock::optimizedOutConstant(TempAllocator& alloc)
{
    // If the first instruction is a MConstant(MagicValue(JS_OPTIMIZED_OUT))
    // then reuse it.
    MInstruction* ins = *begin();
    if (ins->type() == MIRType_MagicOptimizedOut)
        return ins->toConstant();

    MConstant* constant = MConstant::New(alloc, MagicValue(JS_OPTIMIZED_OUT));
    insertBefore(ins, constant);
    return constant;
}

bool
MBasicBlock::linkOsrValues(MStart* start)
{
    MOZ_ASSERT(start->startType() == MStart::StartType_Osr);

    MResumePoint* res = start->resumePoint();

    for (uint32_t i = 0; i < stackDepth(); i++) {
        MDefinition* def = slots_[i];
        MInstruction* cloneRp = nullptr;
        if (i == info().scopeChainSlot()) {
            if (def->isOsrScopeChain())
                cloneRp = def->toOsrScopeChain();
        } else if (i == info().returnValueSlot()) {
            if (def->isOsrReturnValue())
                cloneRp = def->toOsrReturnValue();
        } else if (info().hasArguments() && i == info().argsObjSlot()) {
            MOZ_ASSERT(def->isConstant() || def->isOsrArgumentsObject());
            MOZ_ASSERT_IF(def->isConstant(), def->toConstant()->value() == UndefinedValue());
            if (def->isOsrArgumentsObject())
                cloneRp = def->toOsrArgumentsObject();
        } else {
            MOZ_ASSERT(def->isOsrValue() || def->isGetArgumentsObjectArg() || def->isConstant() ||
                       def->isParameter());

            // A constant Undefined can show up here for an argument slot when
            // the function has an arguments object, but the argument in
            // question is stored on the scope chain.
            MOZ_ASSERT_IF(def->isConstant(), def->toConstant()->value() == UndefinedValue());

            if (def->isOsrValue())
                cloneRp = def->toOsrValue();
            else if (def->isGetArgumentsObjectArg())
                cloneRp = def->toGetArgumentsObjectArg();
            else if (def->isParameter())
                cloneRp = def->toParameter();
        }

        if (cloneRp) {
            MResumePoint* clone = MResumePoint::Copy(graph().alloc(), res);
            if (!clone)
                return false;
            cloneRp->setResumePoint(clone);
        }
    }

    return true;
}

bool
Loop::hoistInstructions(InstructionQueue &toHoist)
{
    // Iterate in post-order (uses before definitions)
    for (int32_t i = toHoist.length() - 1; i >= 0; i--) {
        MInstruction *ins = toHoist[i];

        // Don't hoist a cheap constant if it doesn't enable us to hoist one of
        // its uses. We want those instructions as close as possible to their
        // use, to facilitate folding and minimize register pressure.
        if (requiresHoistedUse(ins)) {
            bool loopInvariantUse = false;
            for (MUseDefIterator use(ins); use; use++) {
                if (use.def()->isLoopInvariant()) {
                    loopInvariantUse = true;
                    break;
                }
            }

            if (!loopInvariantUse)
                ins->setNotLoopInvariant();
        }
    }

    // Move all instructions to the preLoop_ block just before the control instruction.
    for (size_t i = 0; i < toHoist.length(); i++) {
        MInstruction *ins = toHoist[i];

        // Loads may have an implicit dependency on either stores (effectful instructions) or
        // control instructions so we should never move these.
        JS_ASSERT(!ins->isControlInstruction());
        JS_ASSERT(!ins->isEffectful());
        JS_ASSERT(ins->isMovable());

        if (!ins->isLoopInvariant())
            continue;

        if (checkHotness(ins->block())) {
            ins->block()->moveBefore(preLoop_->lastIns(), ins);
            ins->setNotLoopInvariant();
        }
    }

    return true;
}

bool
AllDoublePolicy::adjustInputs(TempAllocator &alloc, MInstruction *ins)
{
    for (size_t i = 0, e = ins->numOperands(); i < e; i++) {
        MDefinition *in = ins->getOperand(i);
        if (in->type() == MIRType_Double)
            continue;

        MInstruction *replace = MToDouble::New(alloc, in);

        ins->block()->insertBefore(ins, replace);
        ins->replaceOperand(i, replace);

        if (!replace->typePolicy()->adjustInputs(alloc, replace))
            return false;
    }

    return true;
}

// Fold AddIs with one variable and two or more constants into one AddI.
static void AnalyzeAdd(TempAllocator& alloc, MAdd* add) {
  if (add->specialization() != MIRType::Int32 || add->isRecoveredOnBailout()) {
    return;
  }

  if (!add->hasUses()) {
    return;
  }

  JitSpew(JitSpew_FLAC, "analyze add: %s%u", add->opName(), add->id());

  SimpleLinearSum sum = ExtractLinearSum(add);
  if (sum.constant == 0 || !sum.term) {
    return;
  }

  // Determine which operand is the constant.
  int idx = add->getOperand(0)->isConstant() ? 0 : 1;
  if (add->getOperand(idx)->isConstant()) {
    // Do not replace an add where the outcome is the same add instruction.
    MOZ_ASSERT(add->getOperand(idx)->toConstant()->type() == MIRType::Int32);
    if (sum.term == add->getOperand(1 - idx) ||
        sum.constant == add->getOperand(idx)->toConstant()->toInt32()) {
      return;
    }
  }

  MInstruction* rhs = MConstant::New(alloc, Int32Value(sum.constant));
  add->block()->insertBefore(add, rhs);

  MAdd* addNew =
      MAdd::New(alloc, sum.term, rhs, MIRType::Int32, add->truncateKind());

  add->replaceAllLiveUsesWith(addNew);
  add->block()->insertBefore(add, addNew);
  JitSpew(JitSpew_FLAC, "replaced with: %s%u", addNew->opName(), addNew->id());
  JitSpew(JitSpew_FLAC, "and constant: %s%u (%d)", rhs->opName(), rhs->id(),
          sum.constant);

  // Mark the stale nodes as RecoveredOnBailout since the Sink pass has
  // been run before this pass. DCE will then remove the unused nodes.
  markNodesAsRecoveredOnBailout(add);
}

// Iterate backward on all instruction and attempt to truncate operations for
// each instruction which respect the following list of predicates: Has been
// analyzed by range analysis, the range has no rounding errors, all uses cases
// are truncating the result.
//
// If the truncation of the operation is successful, then the instruction is
// queue for later updating the graph to restore the type correctness by
// converting the operands that need to be truncated.
//
// We iterate backward because it is likely that a truncated operation truncates
// some of its operands.
bool
RangeAnalysis::truncate()
{
    IonSpew(IonSpew_Range, "Do range-base truncation (backward loop)");

    Vector<MInstruction *, 16, SystemAllocPolicy> worklist;

    for (PostorderIterator block(graph_.poBegin()); block != graph_.poEnd(); block++) {
        for (MInstructionReverseIterator iter(block->rbegin()); iter != block->rend(); iter++) {
            // Set truncated flag if range analysis ensure that it has no
            // rounding errors and no freactional part.
            const Range *r = iter->range();
            if (!r || r->hasRoundingErrors())
                continue;

            // Ensure all observable uses are truncated.
            if (!AllUsesTruncate(*iter))
                continue;

            // Truncate this instruction if possible.
            if (!iter->truncate())
                continue;

            // Delay updates of inputs/outputs to avoid creating node which
            // would be removed by the truncation of the next operations.
            iter->setInWorklist();
            if (!worklist.append(*iter))
                return false;
        }
    }

    // Update inputs/outputs of truncated instructions.
    IonSpew(IonSpew_Range, "Do graph type fixup (dequeue)");
    while (!worklist.empty()) {
        MInstruction *ins = worklist.popCopy();
        ins->setNotInWorklist();
        RemoveTruncatesOnOutput(ins);
        AdjustTruncatedInputs(ins);
    }

    return true;
}

bool
CallPolicy::adjustInputs(TempAllocator &alloc, MInstruction *ins)
{
    MCall *call = ins->toCall();

    MDefinition *func = call->getFunction();
    if (func->type() != MIRType_Object) {
        MInstruction *unbox = MUnbox::New(alloc, func, MIRType_Object, MUnbox::Fallible);
        call->block()->insertBefore(call, unbox);
        call->replaceFunction(unbox);

        if (!unbox->typePolicy()->adjustInputs(alloc, unbox))
            return false;
    }

    for (uint32_t i = 0; i < call->numStackArgs(); i++)
        EnsureOperandNotFloat32(alloc, call, MCall::IndexOfStackArg(i));

    return true;
}

// Test whether any instruction in the loop possiblyCalls().
static bool
LoopContainsPossibleCall(MIRGraph &graph, MBasicBlock *header, MBasicBlock *backedge)
{
    for (auto i(graph.rpoBegin(header)); ; ++i) {
        MOZ_ASSERT(i != graph.rpoEnd(), "Reached end of graph searching for blocks in loop");
        MBasicBlock *block = *i;
        if (!block->isMarked())
            continue;

        for (auto insIter(block->begin()), insEnd(block->end()); insIter != insEnd; ++insIter) {
            MInstruction *ins = *insIter;
            if (ins->possiblyCalls()) {
                JitSpew(JitSpew_LICM, "    Possile call found at %s%u", ins->opName(), ins->id());
                return true;
            }
        }

        if (block == backedge)
            break;
    }
    return false;
}

Loop::LoopReturn
Loop::iterateLoopBlocks(MBasicBlock *current)
{
    // Visited.
    current->mark();

    // Hoisting requires more finesse if the loop contains a block that
    // self-dominates: there exists control flow that may enter the loop
    // without passing through the loop preheader.
    //
    // Rather than perform a complicated analysis of the dominance graph,
    // just return a soft error to ignore this loop.
    if (current->immediateDominator() == current)
        return LoopReturn_Skip;

    // If we haven't reached the loop header yet, recursively explore predecessors
    // if we haven't seen them already.
    if (current != header_) {
        for (size_t i = 0; i < current->numPredecessors(); i++) {
            if (current->getPredecessor(i)->isMarked())
                continue;
            LoopReturn lr = iterateLoopBlocks(current->getPredecessor(i));
            if (lr != LoopReturn_Success)
                return lr;
        }
    }

    // Add all instructions in this block (but the control instruction) to the worklist
    for (MInstructionIterator i = current->begin(); i != current->end(); i++) {
        MInstruction *ins = *i;

        if (ins->isMovable() && !ins->isEffectful()) {
            if (!insertInWorklist(ins))
                return LoopReturn_Error;
        }
    }
    return LoopReturn_Success;
}

// In preparation for hoisting an instruction, hoist any of its operands which
// were too cheap to hoist on their own.
static void
MoveDeferredOperands(MInstruction *ins, MInstruction *hoistPoint, bool hasCalls)
{
    // If any of our operands were waiting for a user to be hoisted, make a note
    // to hoist them.
    for (size_t i = 0, e = ins->numOperands(); i != e; ++i) {
        MDefinition *op = ins->getOperand(i);
        if (!IsInLoop(op))
            continue;
        MOZ_ASSERT(RequiresHoistedUse(op, hasCalls),
                   "Deferred loop-invariant operand is not cheap");
        MInstruction *opIns = op->toInstruction();

        // Recursively move the operands. Note that the recursion is bounded
        // because we require RequiresHoistedUse to be set at each level.
        MoveDeferredOperands(opIns, hoistPoint, hasCalls);

        JitSpew(JitSpew_LICM, "    Hoisting %s%u (now that a user will be hoisted)",
                opIns->opName(), opIns->id());

        opIns->block()->moveBefore(hoistPoint, opIns);
    }
}

bool
SimdShufflePolicy::adjustInputs(TempAllocator& alloc, MInstruction* ins)
{
    MSimdGeneralShuffle* s = ins->toSimdGeneralShuffle();

    for (unsigned i = 0; i < s->numVectors(); i++)
        MOZ_ASSERT(ins->getOperand(i)->type() == ins->typePolicySpecialization());

    // Next inputs are the lanes, which need to be int32
    for (unsigned i = 0; i < s->numLanes(); i++) {
        MDefinition* in = ins->getOperand(s->numVectors() + i);
        if (in->type() == MIRType_Int32)
            continue;

        MInstruction* replace = MToInt32::New(alloc, in, MacroAssembler::IntConversion_NumbersOnly);
        ins->block()->insertBefore(ins, replace);
        ins->replaceOperand(s->numVectors() + i, replace);
        if (!replace->typePolicy()->adjustInputs(alloc, replace))
            return false;
    }

    return true;
}

bool
SimdScalarPolicy<Op>::staticAdjustInputs(TempAllocator &alloc, MInstruction *ins)
{
    MOZ_ASSERT(IsSimdType(ins->type()));
    MIRType scalarType = SimdTypeToScalarType(ins->type());

    MDefinition *in = ins->getOperand(Op);
    if (in->type() == scalarType)
        return true;

    MInstruction *replace;
    if (scalarType == MIRType_Int32) {
        replace = MTruncateToInt32::New(alloc, in);
    } else {
        MOZ_ASSERT(scalarType == MIRType_Float32);
        replace = MToFloat32::New(alloc, in);
    }

    ins->block()->insertBefore(ins, replace);
    ins->replaceOperand(Op, replace);

    return replace->typePolicy()->adjustInputs(alloc, replace);
}

void
LoopUnroller::makeReplacementInstruction(MInstruction *ins)
{
    MDefinitionVector inputs(alloc);
    for (size_t i = 0; i < ins->numOperands(); i++) {
        MDefinition *old = ins->getOperand(i);
        MDefinition *replacement = getReplacementDefinition(old);
        if (!inputs.append(replacement))
            CrashAtUnhandlableOOM("LoopUnroller::makeReplacementDefinition");
    }

    MInstruction *clone = ins->clone(alloc, inputs);

    unrolledBackedge->add(clone);

    if (!unrolledDefinitions.putNew(ins, clone))
        CrashAtUnhandlableOOM("LoopUnroller::makeReplacementDefinition");

    if (MResumePoint *old = ins->resumePoint()) {
        MResumePoint *rp = makeReplacementResumePoint(unrolledBackedge, old);
        clone->setResumePoint(rp);
    }
}