[llvm-commits] [llvm] r92800 - /llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
Chris Lattner
sabre at nondot.org
Tue Jan 5 15:00:30 PST 2010
Author: lattner
Date: Tue Jan 5 17:00:30 2010
New Revision: 92800
URL: http://llvm.org/viewvc/llvm-project?rev=92800&view=rev
Log:
simplify this code.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=92800&r1=92799&r2=92800&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Tue Jan 5 17:00:30 2010
@@ -456,123 +456,80 @@
Instruction *Src = dyn_cast<Instruction>(CI.getOperand(0));
if (!Src || !Src->hasOneUse())
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 *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
// expression tree to something weird like i93 unless the source is also
// strange.
- if ((isa<VectorType>(DestTy) ||
- ShouldChangeType(Src->getType(), DestTy)) &&
- CanEvaluateInDifferentType(Src, DestTy,
- CI.getOpcode(), NumCastsRemoved)) {
+ if (!isa<VectorType>(DestTy) && !ShouldChangeType(SrcTy, DestTy))
+ return 0;
+
+ // 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
- // eliminates the cast, so it is always a win. If this is a zero-extension,
- // we need to do an AND to maintain the clear top-part of the computation,
- // so we require that the input have eliminated at least one cast. If this
- // is a sign extension, we insert two new casts (to do the extension) so we
- // require that two casts have been eliminated.
- bool DoXForm = false;
- bool JustReplace = false;
- switch (CI.getOpcode()) {
- default:
- // All the others use floating point so we shouldn't actually
- // get here because of the check above.
- llvm_unreachable("Unknown cast type");
- case Instruction::Trunc:
- DoXForm = true;
- 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);
+ // eliminates the cast, so it is always a win.
+ break;
+ case Instruction::ZExt:
+ // If this is a zero-extension, we need to do an AND to maintain the clear
+ // top-part of the computation, so we require that the input have eliminated
+ // at least one cast.
+ if (NumCastsRemoved < 1)
+ return 0;
+ break;
+ case Instruction::SExt:
+ // If this is a sign extension, we insert two new shifts (to do the
+ // extension) so we require that two casts have been eliminated.
+ if (NumCastsRemoved < 2)
+ return 0;
+ break;
+ }
+
+ DEBUG(errs() << "ICE: EvaluateInDifferentType converting expression type"
+ " to avoid cast: " << CI);
+ Value *Res = EvaluateInDifferentType(Src, DestTy,
+ CI.getOpcode() == Instruction::SExt);
+ assert(Res->getType() == DestTy);
- // 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);
+ 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);
- }
- }
- }
+ // We need to emit a cast to truncate, then a cast to sext.
+ return new SExtInst(Builder->CreateTrunc(Res, Src->getType()), DestTy);
+ }
}
-
- return 0;
}
Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
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