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Misc simplifications to InstCombiner::commonIntCastTransforms. Most of

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the changes are allowed by not calling this function for bitcasts.  
The Instruction::AShr case is dead because 
SimplifyDemandedInstructionBits handles that case.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75514 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2009-07-13 21:45:57 +00:00
parent ea670f1dd8
commit 65445c5b14
1 changed files with 17 additions and 60 deletions
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77
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -8288,11 +8288,10 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
// Attempt to propagate the cast into the instruction for int->int casts.
int NumCastsRemoved = 0;
if (!isa<BitCastInst>(CI) &&
// Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
(isSafeIntegerType(DestTy->getScalarType()) ||
// Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
if ((isSafeIntegerType(DestTy->getScalarType()) ||
!isSafeIntegerType(SrcI->getType()->getScalarType())) &&
CanEvaluateInDifferentType(SrcI, DestTy,
CI.getOpcode(), NumCastsRemoved)) {
@ -8366,7 +8365,6 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
switch (CI.getOpcode()) {
default: LLVM_UNREACHABLE("Unknown cast type!");
case Instruction::Trunc:
case Instruction::BitCast:
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
case Instruction::ZExt: {
@ -8409,16 +8407,12 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
case Instruction::Or:
case Instruction::Xor:
// If we are discarding information, rewrite.
if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
// Don't insert two casts if they cannot be eliminated. We allow
// two casts to be inserted if the sizes are the same. This could
// only be converting signedness, which is a noop.
if (DestBitSize == SrcBitSize ||
!ValueRequiresCast(CI.getOpcode(), Op1, DestTy,TD) ||
if (DestBitSize < SrcBitSize && DestBitSize != 1) {
// Don't insert two casts unless at least one can be eliminated.
if (!ValueRequiresCast(CI.getOpcode(), Op1, DestTy, TD) ||
!ValueRequiresCast(CI.getOpcode(), Op0, DestTy, TD)) {
Instruction::CastOps opcode = CI.getOpcode();
Value *Op0c = InsertCastBefore(opcode, Op0, DestTy, *SrcI);
Value *Op1c = InsertCastBefore(opcode, Op1, DestTy, *SrcI);
Value *Op0c = InsertCastBefore(Instruction::Trunc, Op0, DestTy, *SrcI);
Value *Op1c = InsertCastBefore(Instruction::Trunc, Op1, DestTy, *SrcI);
return BinaryOperator::Create(
cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
}
@ -8434,55 +8428,18 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
Context->getConstantInt(CI.getType(), 1));
}
break;
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::SRem:
case Instruction::URem:
// If we are just changing the sign, rewrite.
if (DestBitSize == SrcBitSize) {
// Don't insert two casts if they cannot be eliminated. We allow
// two casts to be inserted if the sizes are the same. This could
// only be converting signedness, which is a noop.
if (!ValueRequiresCast(CI.getOpcode(), Op1, DestTy, TD) ||
!ValueRequiresCast(CI.getOpcode(), Op0, DestTy, TD)) {
Value *Op0c = InsertCastBefore(Instruction::BitCast,
Op0, DestTy, *SrcI);
Value *Op1c = InsertCastBefore(Instruction::BitCast,
Op1, DestTy, *SrcI);
return BinaryOperator::Create(
cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
}
}
break;
case Instruction::Shl:
// Allow changing the sign of the source operand. Do not allow
// changing the size of the shift, UNLESS the shift amount is a
// constant. We must not change variable sized shifts to a smaller
// size, because it is undefined to shift more bits out than exist
// in the value.
if (DestBitSize == SrcBitSize ||
(DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
Instruction::CastOps opcode = (DestBitSize == SrcBitSize ?
Instruction::BitCast : Instruction::Trunc);
Value *Op0c = InsertCastBefore(opcode, Op0, DestTy, *SrcI);
Value *Op1c = InsertCastBefore(opcode, Op1, DestTy, *SrcI);
case Instruction::Shl: {
// Canonicalize trunc inside shl, if we can.
ConstantInt *CI = dyn_cast<ConstantInt>(Op1);
if (CI && DestBitSize < SrcBitSize &&
CI->getLimitedValue(DestBitSize) < DestBitSize) {
Value *Op0c = InsertCastBefore(Instruction::Trunc, Op0, DestTy, *SrcI);
Value *Op1c = InsertCastBefore(Instruction::Trunc, Op1, DestTy, *SrcI);
return BinaryOperator::CreateShl(Op0c, Op1c);
}
break;
case Instruction::AShr:
// If this is a signed shr, and if all bits shifted in are about to be
// truncated off, turn it into an unsigned shr to allow greater
// simplifications.
if (DestBitSize < SrcBitSize &&
isa<ConstantInt>(Op1)) {
uint32_t ShiftAmt = cast<ConstantInt>(Op1)->getLimitedValue(SrcBitSize);
if (SrcBitSize > ShiftAmt && SrcBitSize-ShiftAmt >= DestBitSize) {
// Insert the new logical shift right.
return BinaryOperator::CreateLShr(Op0, Op1);
}
}
break;
}
}
return 0;
}