diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 39 |
1 files changed, 13 insertions, 26 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 13f60716f2e..07dd2874725 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -783,8 +783,7 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) { /// This function works on both vectors and scalars. For vectors, the result is /// the number of bits known sign extended in each element. /// -static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, - unsigned &NumCastsRemoved, TargetData *TD) { +static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) { assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() && "Can't sign extend type to a smaller type"); // If this is a constant, return the number of sign bits the extended version @@ -795,16 +794,9 @@ static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, Instruction *I = dyn_cast<Instruction>(V); if (!I) return 0; - // If this is a truncate from the destination type, we can trivially eliminate - // it, and this will remove a cast overall. - if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) { - // If the operand of the truncate is itself a cast, and is eliminable, do - // not count this as an eliminable cast. We would prefer to eliminate those - // two casts first. - if (!isa<CastInst>(I->getOperand(0)) && I->hasOneUse()) - ++NumCastsRemoved; + // If this is a truncate from the dest type, we can trivially eliminate it. + if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) return ComputeNumSignBits(I->getOperand(0), TD); - } // We can't extend or shrink something that has multiple uses: doing so would // require duplicating the instruction in general, which isn't profitable. @@ -819,23 +811,23 @@ static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, case Instruction::Or: case Instruction::Xor: // These operators can all arbitrarily be extended or truncated. - Tmp1 = CanEvaluateSExtd(I->getOperand(0), Ty, NumCastsRemoved, TD); + Tmp1 = CanEvaluateSExtd(I->getOperand(0), Ty, TD); if (Tmp1 == 0) return 0; - Tmp2 = CanEvaluateSExtd(I->getOperand(1), Ty, NumCastsRemoved, TD); + Tmp2 = CanEvaluateSExtd(I->getOperand(1), Ty, TD); return std::min(Tmp1, Tmp2); case Instruction::Add: case Instruction::Sub: // Add/Sub can have at most one carry/borrow bit. - Tmp1 = CanEvaluateSExtd(I->getOperand(0), Ty, NumCastsRemoved, TD); + Tmp1 = CanEvaluateSExtd(I->getOperand(0), Ty, TD); if (Tmp1 == 0) return 0; - Tmp2 = CanEvaluateSExtd(I->getOperand(1), Ty, NumCastsRemoved, TD); + Tmp2 = CanEvaluateSExtd(I->getOperand(1), Ty, TD); if (Tmp2 == 0) return 0; return std::min(Tmp1, Tmp2)-1; case Instruction::Mul: // These operators can all arbitrarily be extended or truncated. - if (!CanEvaluateSExtd(I->getOperand(0), Ty, NumCastsRemoved, TD)) + if (!CanEvaluateSExtd(I->getOperand(0), Ty, TD)) return 0; - if (!CanEvaluateSExtd(I->getOperand(1), Ty, NumCastsRemoved, TD)) + if (!CanEvaluateSExtd(I->getOperand(1), Ty, TD)) return 0; return 1; // IMPROVE? @@ -856,9 +848,9 @@ static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, } case Instruction::Select: { SelectInst *SI = cast<SelectInst>(I); - Tmp1 = CanEvaluateSExtd(SI->getTrueValue(), Ty, NumCastsRemoved, TD); + Tmp1 = CanEvaluateSExtd(SI->getTrueValue(), Ty, TD); if (Tmp1 == 0) return 0; - Tmp2 = CanEvaluateSExtd(SI->getFalseValue(), Ty, NumCastsRemoved,TD); + Tmp2 = CanEvaluateSExtd(SI->getFalseValue(), Ty, TD); return std::min(Tmp1, Tmp2); } case Instruction::PHI: { @@ -869,8 +861,7 @@ static unsigned CanEvaluateSExtd(Value *V, const Type *Ty, unsigned Result = ~0U; for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { Result = std::min(Result, - CanEvaluateSExtd(PN->getIncomingValue(i), Ty, - NumCastsRemoved, TD)); + CanEvaluateSExtd(PN->getIncomingValue(i), Ty, TD)); if (Result == 0) return 0; } return Result; @@ -911,11 +902,7 @@ Instruction *InstCombiner::visitSExt(SExtInst &CI) { // expression tree to something weird like i93 unless the source is also // strange. if (isa<VectorType>(DestTy) || ShouldChangeType(SrcTy, DestTy)) { - unsigned NumCastsRemoved = 0; - // Check to see if we can do this transformation, and if so, how many bits - // of the promoted expression will be known copies of the sign bit in the - // result. - unsigned NumBitsSExt = CanEvaluateSExtd(Src, DestTy, NumCastsRemoved, TD); + unsigned NumBitsSExt = CanEvaluateSExtd(Src, DestTy, TD); if (NumBitsSExt == 0) return 0; |
