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Bug 788476 - Fold x & -1 to x. r=dvander

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This commit is contained in:
Jan de Mooij 2012-09-07 12:53:02 +02:00
parent cb5e844dd9
commit 72b9ce0878
2 changed files with 19 additions and 7 deletions
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6
js/src/ion/MIR.cpp
View File

@ -519,6 +519,12 @@ MBinaryBitwiseInstruction::foldsTo(bool useValueNumbers)
if (IsConstant(rhs, 0))
return foldIfZero(1);
if (IsConstant(lhs, -1))
return foldIfNegOne(0);
if (IsConstant(rhs, -1))
return foldIfNegOne(1);
if (EqualValues(useValueNumbers, lhs, rhs))
return foldIfEqual();

20
js/src/ion/MIR.h
View File

@ -1886,6 +1886,7 @@ class MBinaryBitwiseInstruction
MDefinition *foldsTo(bool useValueNumbers);
virtual MDefinition *foldIfZero(size_t operand) = 0;
virtual MDefinition *foldIfNegOne(size_t operand) = 0;
virtual MDefinition *foldIfEqual() = 0;
virtual void infer(const TypeOracle::Binary &b);
@ -1912,7 +1913,9 @@ class MBitAnd : public MBinaryBitwiseInstruction
MDefinition *foldIfZero(size_t operand) {
return getOperand(operand); // 0 & x => 0;
}
MDefinition *foldIfNegOne(size_t operand) {
return getOperand(1 - operand); // x & -1 => x
}
MDefinition *foldIfEqual() {
return getOperand(0); // x & x => x;
}
@ -1931,14 +1934,12 @@ class MBitOr : public MBinaryBitwiseInstruction
MDefinition *foldIfZero(size_t operand) {
return getOperand(1 - operand); // 0 | x => x, so if ith is 0, return (1-i)th
}
MDefinition *foldIfNegOne(size_t operand) {
return getOperand(operand); // x | -1 => -1
}
MDefinition *foldIfEqual() {
return getOperand(0); // x | x => x
}
MDefinition *foldIfNegOne(size_t operand) {
return getOperand(operand);
}
};
class MBitXor : public MBinaryBitwiseInstruction
@ -1954,7 +1955,9 @@ class MBitXor : public MBinaryBitwiseInstruction
MDefinition *foldIfZero(size_t operand) {
return getOperand(1 - operand); // 0 ^ x => x
}
MDefinition *foldIfNegOne(size_t operand) {
return this;
}
MDefinition *foldIfEqual() {
return MConstant::New(Int32Value(0));
}
@ -1969,6 +1972,9 @@ class MShiftInstruction
{ }
public:
MDefinition *foldIfNegOne(size_t operand) {
return this;
}
MDefinition *foldIfEqual() {
return this;
}