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