Ejemplo n.º 1
0
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);
    if (!ins->isMovable())
        replace->setNotMovable();

    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;
}
Ejemplo n.º 2
0
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.
        JS_ASSERT(inputType != MIRType_Value);
        ins->replaceOperand(0, boxAt(alloc, ins, ins->getOperand(0)));
        return true;
    }

    // Input is a value. Unbox the input to the requested type.
    if (inputType == MIRType_Value) {
        JS_ASSERT(outputType != MIRType_Value);

        // We can't unbox a value to null/undefined/lazyargs. So keep output
        // also a value.
        if (IsNullOrUndefined(outputType) || outputType == MIRType_MagicOptimizedArguments) {
            JS_ASSERT(!ins->hasDefUses());
            ins->setResultType(MIRType_Value);
            return true;
        }

        MUnbox *unbox = MUnbox::New(alloc, ins->getOperand(0), outputType, MUnbox::TypeBarrier);
        ins->block()->insertBefore(ins, unbox);
        ins->replaceOperand(0, unbox);
        return true;
    }

    // In the remaining cases we will alway bail. OutputType doesn't matter.
    // Take inputType so we can use redefine during lowering.
    JS_ASSERT(ins->alwaysBails());
    ins->setResultType(inputType);

    return true;
}