C++ MInstruction::setDependency方法代码示例

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;
}

// This pass annotates every load instruction with the last store instruction
// on which it depends. The algorithm is optimistic in that it ignores explicit
// dependencies and only considers loads and stores.
//
// Loads inside loops only have an implicit dependency on a store before the
// loop header if no instruction inside the loop body aliases it. To calculate
// this efficiently, we maintain a list of maybe-invariant loads and the combined
// alias set for all stores inside the loop. When we see the loop's backedge, this
// information is used to mark every load we wrongly assumed to be loop invariant as
// having an implicit dependency on the last instruction of the loop header, so that
// it's never moved before the loop header.
//
// The algorithm depends on the invariant that both control instructions and effectful
// instructions (stores) are never hoisted.
bool
AliasAnalysis::analyze()
{
    Vector<MInstructionVector, AliasSet::NumCategories, JitAllocPolicy> stores(alloc());

    // Initialize to the first instruction.
    MInstruction* firstIns = *graph_.entryBlock()->begin();
    for (unsigned i = 0; i < AliasSet::NumCategories; i++) {
        MInstructionVector defs(alloc());
        if (!defs.append(firstIns))
            return false;
        if (!stores.append(Move(defs)))
            return false;
    }

    // Type analysis may have inserted new instructions. Since this pass depends
    // on the instruction number ordering, all instructions are renumbered.
    uint32_t newId = 0;

    for (ReversePostorderIterator block(graph_.rpoBegin()); block != graph_.rpoEnd(); block++) {
        if (mir->shouldCancel("Alias Analysis (main loop)"))
            return false;

        if (block->isLoopHeader()) {
            JitSpew(JitSpew_Alias, "Processing loop header %d", block->id());
            loop_ = new(alloc()) LoopAliasInfo(alloc(), loop_, *block);
        }

        for (MPhiIterator def(block->phisBegin()), end(block->phisEnd()); def != end; ++def)
            def->setId(newId++);

        for (MInstructionIterator def(block->begin()), end(block->begin(block->lastIns()));
             def != end;
             ++def)
        {
            def->setId(newId++);

            AliasSet set = def->getAliasSet();
            if (set.isNone())
                continue;

            // For the purposes of alias analysis, all recoverable operations
            // are treated as effect free as the memory represented by these
            // operations cannot be aliased by others.
            if (def->canRecoverOnBailout())
                continue;

            if (set.isStore()) {
                for (AliasSetIterator iter(set); iter; iter++) {
                    if (!stores[*iter].append(*def))
                        return false;
                }

                if (JitSpewEnabled(JitSpew_Alias)) {
                    Fprinter& out = JitSpewPrinter();
                    out.printf("Processing store ");
                    def->printName(out);
                    out.printf(" (flags %x)\n", set.flags());
                }
            } else {
                // Find the most recent store on which this instruction depends.
                MInstruction* lastStore = firstIns;

                for (AliasSetIterator iter(set); iter; iter++) {
                    MInstructionVector& aliasedStores = stores[*iter];
                    for (int i = aliasedStores.length() - 1; i >= 0; i--) {
                        MInstruction* store = aliasedStores[i];
                        if (genericMightAlias(*def, store) != MDefinition::AliasType::NoAlias &&
                            def->mightAlias(store) != MDefinition::AliasType::NoAlias &&
                            BlockMightReach(store->block(), *block))
                        {
                            if (lastStore->id() < store->id())
                                lastStore = store;
                            break;
                        }
                    }
                }

                def->setDependency(lastStore);
                IonSpewDependency(*def, lastStore, "depends", "");

                // If the last store was before the current loop, we assume this load
                // is loop invariant. If a later instruction writes to the same location,
                // we will fix this at the end of the loop.
                if (loop_ && lastStore->id() < loop_->firstInstruction()->id()) {
                    if (!loop_->addInvariantLoad(*def))
//.........这里部分代码省略.........

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

    // Special case when output is a Float32, but input isn't.
    if (outputType == MIRType_Float32 && inputType != MIRType_Float32) {
        // Create a MToFloat32 to add between the MFilterTypeSet and
        // its uses.
        MInstruction* replace = MToFloat32::New(alloc, ins);
        ins->justReplaceAllUsesWithExcept(replace);
        ins->block()->insertAfter(ins, replace);

        // Reset the type to not MIRType_Float32
        // Note: setResultType shouldn't happen in TypePolicies,
        //       Here it is fine, since there is just one use we just
        //       added ourself. And the resulting type after MToFloat32
        //       equals the original type.
        ins->setResultType(ins->resultTypeSet()->getKnownMIRType());
        outputType = ins->type();

        // Do the type analysis
        if (!replace->typePolicy()->adjustInputs(alloc, replace))
            return false;

        // Fall through to let the MFilterTypeSet adjust its input based
        // on its new 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;
}