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1. Make more use of getLowBitsSet/getHighBitsSet.

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2. Use APInt[] instead of "X & SignBit".
3. Clean up some codes.
4. Make the expression like "ShiftAmt = ShiftAmtC->getZExtValue()" safe.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35424 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-28 15:02:20 +00:00
parent 9dea3a340a
commit e9e03f6b76
1 changed files with 16 additions and 13 deletions
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29
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1313,7 +1313,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
RHSKnownOne <<= ShiftAmt; RHSKnownOne <<= ShiftAmt;
// low bits known zero. // low bits known zero.
if (ShiftAmt) if (ShiftAmt)
RHSKnownZero |= APInt::getAllOnesValue(ShiftAmt).zextOrCopy(BitWidth); RHSKnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
} }
break; break;
case Instruction::LShr: case Instruction::LShr:
@ -5608,7 +5608,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
// of a signed value. // of a signed value.
// //
if (Op1->getZExtValue() >= TypeBits) { // shift amount always <= 32 bits if (Op1->getValue().getActiveBits() > 64 || Op1->getZExtValue() >= TypeBits) {
if (I.getOpcode() != Instruction::AShr) if (I.getOpcode() != Instruction::AShr)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType())); return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
else { else {
@ -5751,8 +5751,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
// operation. // operation.
// //
if (isValid && !isLeftShift && I.getOpcode() == Instruction::AShr) { if (isValid && !isLeftShift && I.getOpcode() == Instruction::AShr) {
isValid = ((Op0C->getValue() & APInt::getSignBit(TypeBits)) != 0) == isValid = Op0C->getValue()[TypeBits-1] == highBitSet;
highBitSet;
} }
if (isValid) { if (isValid) {
@ -5777,9 +5776,10 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) { if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) {
ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1)); ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1));
// These shift amounts are always <= 32 bits. uint32_t ShiftAmt1 = ShiftAmt1C->getValue().getActiveBits() > 64 ?
unsigned ShiftAmt1 = (unsigned)ShiftAmt1C->getZExtValue(); TypeBits : (uint32_t)ShiftAmt1C->getZExtValue();
unsigned ShiftAmt2 = (unsigned)Op1->getZExtValue(); uint32_t ShiftAmt2 = Op1->getValue().getActiveBits() > 64 ?
TypeBits : (uint32_t)Op1->getZExtValue();
assert(ShiftAmt2 != 0 && "Should have been simplified earlier"); assert(ShiftAmt2 != 0 && "Should have been simplified earlier");
if (ShiftAmt1 == 0) return 0; // Will be simplified in the future. if (ShiftAmt1 == 0) return 0; // Will be simplified in the future.
Value *X = ShiftOp->getOperand(0); Value *X = ShiftOp->getOperand(0);
@ -5805,7 +5805,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
BinaryOperator::createAShr(X, ConstantInt::get(Ty, AmtSum)); BinaryOperator::createAShr(X, ConstantInt::get(Ty, AmtSum));
InsertNewInstBefore(Shift, I); InsertNewInstBefore(Shift, I);
APInt Mask(Ty->getMask().lshr(ShiftAmt2)); APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask)); return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
} }
@ -5828,11 +5828,14 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
// generators. // generators.
const Type *SExtType = 0; const Type *SExtType = 0;
switch (Ty->getBitWidth() - ShiftAmt1) { switch (Ty->getBitWidth() - ShiftAmt1) {
case 1 : SExtType = Type::Int1Ty; break; case 1 :
case 8 : SExtType = Type::Int8Ty; break; case 8 :
case 16 : SExtType = Type::Int16Ty; break; case 16 :
case 32 : SExtType = Type::Int32Ty; break; case 32 :
case 64 : SExtType = Type::Int64Ty; break; case 64 :
case 128:
SExtType = IntegerType::get(Ty->getBitWidth() - ShiftAmt1);
break;
default: break; default: break;
} }
if (SExtType) { if (SExtType) {