static inline bool
NeedNegativeZeroCheck(MDefinition *def)
{
// Test if all uses have the same symantic for -0 and 0
for (MUseIterator use = def->usesBegin(); use != def->usesEnd(); use++) {
if (use->node()->isResumePoint())
return true;
MDefinition *use_def = use->node()->toDefinition();
switch (use_def->op()) {
case MDefinition::Op_Add: {
// x + y gives -0, when both x and y are -0
// - When other operand can't produce -0 (i.e. all opcodes, except Mul/Div/ToInt32)
// Remove negative zero check on this operand
// - When both operands can produce -0 (both Mul/Div/ToInt32 opcode)
// We can remove the check eagerly on this operand.
MDefinition *operand = use_def->getOperand(0);
if (operand == def) {
operand = use_def->getOperand(1);
// Don't remove check when both operands are same definition
// As removing it from one operand, will remove it from both.
if (operand == def)
return true;
}
// Check if check is possibly eagerly removed on other operand
// and don't remove check eagerly on this operand in that case.
if (operand->isMul()) {
MMul *mul = operand->toMul();
if (!mul->canBeNegativeZero())
return true;
} else if (operand->isDiv()) {
MDiv *div = operand->toDiv();
if (!div->canBeNegativeZero())
return true;
} else if (operand->isToInt32()) {
MToInt32 *int32 = operand->toToInt32();
if (!int32->canBeNegativeZero())
return true;
} else if (operand->isPhi()) {
return true;
}
break;
}
case MDefinition::Op_StoreElement:
case MDefinition::Op_StoreElementHole:
case MDefinition::Op_LoadElement:
case MDefinition::Op_LoadElementHole:
case MDefinition::Op_LoadTypedArrayElement:
case MDefinition::Op_LoadTypedArrayElementHole:
case MDefinition::Op_CharCodeAt:
case MDefinition::Op_Mod:
case MDefinition::Op_Sub:
// Only allowed to remove check when definition is the second operand
if (use_def->getOperand(0) == def)
return true;
if (use_def->numOperands() > 2) {
for (size_t i = 2; i < use_def->numOperands(); i++) {
if (use_def->getOperand(i) == def)
return true;
}
}
break;
case MDefinition::Op_BoundsCheck:
// Only allowed to remove check when definition is the first operand
if (use_def->getOperand(1) == def)
return true;
break;
case MDefinition::Op_ToString:
case MDefinition::Op_FromCharCode:
case MDefinition::Op_TableSwitch:
case MDefinition::Op_Compare:
case MDefinition::Op_BitAnd:
case MDefinition::Op_BitOr:
case MDefinition::Op_BitXor:
case MDefinition::Op_Abs:
// Always allowed to remove check. No matter which operand.
break;
default:
return true;
}
}
return false;
}
