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[InstCombine] use 'match' to reduce code; NFCI 

llvm-svn: 295991
This commit is contained in:
Sanjay Patel 2017-02-23 16:26:03 +00:00
parent 70293a045b
commit adf2ab16e4
1 changed files with 9 additions and 11 deletions
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20
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -1167,18 +1167,16 @@ Instruction *InstCombiner::visitSExt(SExtInst &CI) {
ShAmt);
}
// If this input is a trunc from our destination, then turn sext(trunc(x))
// If the input is a trunc from the destination type, then turn sext(trunc(x))
// into shifts.
if (TruncInst *TI = dyn_cast<TruncInst>(Src))
if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) {
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
// We need to emit a shl + ashr to do the sign extend.
Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext");
return BinaryOperator::CreateAShr(Res, ShAmt);
}
Value *X;
if (match(Src, m_OneUse(m_Trunc(m_Value(X)))) && X->getType() == DestTy) {
// sext(trunc(X)) --> ashr(shl(X, C), C)
unsigned SrcBitSize = SrcTy->getScalarSizeInBits();
unsigned DestBitSize = DestTy->getScalarSizeInBits();
Constant *ShAmt = ConstantInt::get(DestTy, DestBitSize - SrcBitSize);
return BinaryOperator::CreateAShr(Builder->CreateShl(X, ShAmt), ShAmt);
}
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
return transformSExtICmp(ICI, CI);