bool TypeBarrierPolicy::adjustInputs(TempAllocator& alloc,
MInstruction* def) const {
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;
}
