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Simplify the code a bit more

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25126 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-01-06 07:22:22 +00:00
parent 4d5542ce6e
commit 830ed03e8b
1 changed files with 5 additions and 3 deletions
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8
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3449,13 +3449,15 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantUInt *Op1,
ShiftInst &I) {
bool isLeftShift = I.getOpcode() == Instruction::Shl;
bool isSignedShift = Op0->getType()->isSigned();
bool isUnsignedShift = !isSignedShift;
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
// of a signed value.
//
unsigned TypeBits = Op0->getType()->getPrimitiveSizeInBits();
if (Op1->getValue() >= TypeBits) {
if (!Op0->getType()->isSigned() || isLeftShift)
if (isUnsignedShift || isLeftShift)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
else {
I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
@ -3625,7 +3627,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantUInt *Op1,
// the constant which would cause it to be modified for this
// operation.
//
if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
if (isValid && !isLeftShift && isSignedShift) {
uint64_t Val = Op0C->getRawValue();
isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
}
@ -3665,7 +3667,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantUInt *Op1,
// Check for (A << c1) >> c2 or visaversa. If we are dealing with
// signed types, we can only support the (A >> c1) << c2 configuration,
// because it can not turn an arbitrary bit of A into a sign bit.
if (I.getType()->isUnsigned() || isLeftShift) {
if (isUnsignedShift || isLeftShift) {
// Calculate bitmask for what gets shifted off the edge...
Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
if (isLeftShift)