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simplify this code.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92800 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-05 23:00:30 +00:00
parent d7d1a29003
commit 68c6e8998b
1 changed files with 66 additions and 109 deletions
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175
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -456,123 +456,80 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
Instruction *Src = dyn_cast<Instruction>(CI.getOperand(0)); Instruction *Src = dyn_cast<Instruction>(CI.getOperand(0));
if (!Src || !Src->hasOneUse()) if (!Src || !Src->hasOneUse())
return 0; return 0;
// Check to see if we can eliminate the cast by changing the entire
// computation chain to do the computation in the result type.
const Type *SrcTy = Src->getType(); const Type *SrcTy = Src->getType();
const Type *DestTy = CI.getType(); const Type *DestTy = CI.getType();
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
// Attempt to propagate the cast into the instruction for int->int casts.
int NumCastsRemoved = 0;
// Only do this if the dest type is a simple type, don't convert the // 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 // expression tree to something weird like i93 unless the source is also
// strange. // strange.
if ((isa<VectorType>(DestTy) || if (!isa<VectorType>(DestTy) && !ShouldChangeType(SrcTy, DestTy))
ShouldChangeType(Src->getType(), DestTy)) && return 0;
CanEvaluateInDifferentType(Src, DestTy,
CI.getOpcode(), NumCastsRemoved)) { // Attempt to propagate the cast into the instruction for int->int casts.
int NumCastsRemoved = 0;
if (!CanEvaluateInDifferentType(Src, DestTy, CI.getOpcode(), NumCastsRemoved))
return 0;
switch (CI.getOpcode()) {
default: assert(0 && "not an integer cast");
case Instruction::Trunc:
// If this cast is a truncate, evaluting in a different type always // If this cast is a truncate, evaluting in a different type always
// eliminates the cast, so it is always a win. If this is a zero-extension, // eliminates the cast, so it is always a win.
// we need to do an AND to maintain the clear top-part of the computation, break;
// so we require that the input have eliminated at least one cast. If this case Instruction::ZExt:
// is a sign extension, we insert two new casts (to do the extension) so we // If this is a zero-extension, we need to do an AND to maintain the clear
// require that two casts have been eliminated. // top-part of the computation, so we require that the input have eliminated
bool DoXForm = false; // at least one cast.
bool JustReplace = false; if (NumCastsRemoved < 1)
switch (CI.getOpcode()) { return 0;
default: break;
// All the others use floating point so we shouldn't actually case Instruction::SExt:
// get here because of the check above. // If this is a sign extension, we insert two new shifts (to do the
llvm_unreachable("Unknown cast type"); // extension) so we require that two casts have been eliminated.
case Instruction::Trunc: if (NumCastsRemoved < 2)
DoXForm = true; return 0;
break; break;
case Instruction::ZExt: {
DoXForm = NumCastsRemoved >= 1;
if (!DoXForm && 0) {
// If it's unnecessary to issue an AND to clear the high bits, it's
// always profitable to do this xform.
Value *TryRes = EvaluateInDifferentType(Src, DestTy, false);
APInt Mask(APInt::getBitsSet(DestBitSize, SrcBitSize, DestBitSize));
if (MaskedValueIsZero(TryRes, Mask))
return ReplaceInstUsesWith(CI, TryRes);
if (Instruction *TryI = dyn_cast<Instruction>(TryRes))
if (TryI->use_empty())
EraseInstFromFunction(*TryI);
}
break;
}
case Instruction::SExt: {
DoXForm = NumCastsRemoved >= 2;
if (!DoXForm && !isa<TruncInst>(Src) && 0) {
// If we do not have to emit the truncate + sext pair, then it's always
// profitable to do this xform.
//
// It's not safe to eliminate the trunc + sext pair if one of the
// eliminated cast is a truncate. e.g.
// t2 = trunc i32 t1 to i16
// t3 = sext i16 t2 to i32
// !=
// i32 t1
Value *TryRes = EvaluateInDifferentType(Src, DestTy, true);
unsigned NumSignBits = ComputeNumSignBits(TryRes);
if (NumSignBits > (DestBitSize - SrcBitSize))
return ReplaceInstUsesWith(CI, TryRes);
if (Instruction *TryI = dyn_cast<Instruction>(TryRes))
if (TryI->use_empty())
EraseInstFromFunction(*TryI);
}
break;
}
}
if (DoXForm) {
DEBUG(errs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid cast: " << CI);
Value *Res = EvaluateInDifferentType(Src, DestTy,
CI.getOpcode() == Instruction::SExt);
if (JustReplace)
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
assert(Res->getType() == DestTy);
switch (CI.getOpcode()) {
default: llvm_unreachable("Unknown cast type!");
case Instruction::Trunc:
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
case Instruction::ZExt: {
assert(SrcBitSize < DestBitSize && "Not a zext?");
// If the high bits are already zero, just replace this cast with the
// result.
APInt Mask(APInt::getBitsSet(DestBitSize, SrcBitSize, DestBitSize));
if (MaskedValueIsZero(Res, Mask))
return ReplaceInstUsesWith(CI, Res);
// We need to emit an AND to clear the high bits.
Constant *C = ConstantInt::get(CI.getContext(),
APInt::getLowBitsSet(DestBitSize, SrcBitSize));
return BinaryOperator::CreateAnd(Res, C);
}
case Instruction::SExt: {
// If the high bits are already filled with sign bit, just replace this
// cast with the result.
unsigned NumSignBits = ComputeNumSignBits(Res);
if (NumSignBits > (DestBitSize - SrcBitSize))
return ReplaceInstUsesWith(CI, Res);
// We need to emit a cast to truncate, then a cast to sext.
return new SExtInst(Builder->CreateTrunc(Res, Src->getType()), DestTy);
}
}
}
} }
return 0; DEBUG(errs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid cast: " << CI);
Value *Res = EvaluateInDifferentType(Src, DestTy,
CI.getOpcode() == Instruction::SExt);
assert(Res->getType() == DestTy);
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
switch (CI.getOpcode()) {
default: assert(0 && "Unknown cast type!");
case Instruction::Trunc:
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
case Instruction::ZExt: {
// If the high bits are already zero, just replace this cast with the
// result.
APInt Mask(APInt::getBitsSet(DestBitSize, SrcBitSize, DestBitSize));
if (MaskedValueIsZero(Res, Mask))
return ReplaceInstUsesWith(CI, Res);
// We need to emit an AND to clear the high bits.
Constant *C = ConstantInt::get(CI.getContext(),
APInt::getLowBitsSet(DestBitSize, SrcBitSize));
return BinaryOperator::CreateAnd(Res, C);
}
case Instruction::SExt: {
// If the high bits are already filled with sign bit, just replace this
// cast with the result.
unsigned NumSignBits = ComputeNumSignBits(Res);
if (NumSignBits > (DestBitSize - SrcBitSize))
return ReplaceInstUsesWith(CI, Res);
// We need to emit a cast to truncate, then a cast to sext.
return new SExtInst(Builder->CreateTrunc(Res, Src->getType()), DestTy);
}
}
} }
Instruction *InstCombiner::visitTrunc(TruncInst &CI) { Instruction *InstCombiner::visitTrunc(TruncInst &CI) {