MUseIterator
MNode::replaceOperand(MUseIterator use, MDefinition *ins)
{
MDefinition *used = getOperand(use->index());
if (used == ins)
return use;
MUse *save = *use;
MUseIterator result(used->removeUse(use));
if (ins) {
setOperand(save->index(), ins);
ins->linkUse(save);
}
return result;
}
static void
AnalyzeLsh(TempAllocator &alloc, MLsh *lsh)
{
if (lsh->specialization() != MIRType_Int32)
return;
MDefinition *index = lsh->lhs();
JS_ASSERT(index->type() == MIRType_Int32);
MDefinition *shift = lsh->rhs();
if (!shift->isConstant())
return;
Value shiftValue = shift->toConstant()->value();
if (!shiftValue.isInt32() || !IsShiftInScaleRange(shiftValue.toInt32()))
return;
Scale scale = ShiftToScale(shiftValue.toInt32());
int32_t displacement = 0;
MInstruction *last = lsh;
MDefinition *base = nullptr;
while (true) {
if (!last->hasOneUse())
break;
MUseIterator use = last->usesBegin();
if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isAdd())
break;
MAdd *add = use->consumer()->toDefinition()->toAdd();
if (add->specialization() != MIRType_Int32 || !add->isTruncated())
break;
MDefinition *other = add->getOperand(1 - use->index());
if (other->isConstant()) {
displacement += other->toConstant()->value().toInt32();
} else {
if (base)
break;
base = other;
}
last = add;
}
if (!base) {
uint32_t elemSize = 1 << ScaleToShift(scale);
if (displacement % elemSize != 0)
return;
if (!last->hasOneUse())
return;
MUseIterator use = last->usesBegin();
if (!use->consumer()->isDefinition() || !use->consumer()->toDefinition()->isBitAnd())
return;
MBitAnd *bitAnd = use->consumer()->toDefinition()->toBitAnd();
MDefinition *other = bitAnd->getOperand(1 - use->index());
if (!other->isConstant() || !other->toConstant()->value().isInt32())
return;
uint32_t bitsClearedByShift = elemSize - 1;
uint32_t bitsClearedByMask = ~uint32_t(other->toConstant()->value().toInt32());
if ((bitsClearedByShift & bitsClearedByMask) != bitsClearedByMask)
return;
bitAnd->replaceAllUsesWith(last);
return;
}
MEffectiveAddress *eaddr = MEffectiveAddress::New(alloc, base, index, scale, displacement);
last->replaceAllUsesWith(eaddr);
last->block()->insertAfter(last, eaddr);
}
