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clean up this xform by using m_Trunc. 

llvm-svn: 93092
This commit is contained in:
Chris Lattner 2010-01-10 01:04:31 +00:00
parent 883550afe8
commit c95a7a21b7
1 changed files with 9 additions and 12 deletions
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21
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -1035,20 +1035,17 @@ Instruction *InstCombiner::visitSExt(SExtInst &CI) {
// %a = shl i32 %i, 30
// %d = ashr i32 %a, 30
Value *A = 0;
// FIXME: GENERALIZE WITH SIGN BITS.
// TODO: Eventually this could be subsumed by EvaluateInDifferentType.
ConstantInt *BA = 0, *CA = 0;
if (match(Src, m_AShr(m_Shl(m_Value(A), m_ConstantInt(BA)),
if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)),
m_ConstantInt(CA))) &&
BA == CA && isa<TruncInst>(A)) {
Value *I = cast<TruncInst>(A)->getOperand(0);
if (I->getType() == CI.getType()) {
unsigned MidSize = Src->getType()->getScalarSizeInBits();
unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
I = Builder->CreateShl(I, ShAmtV, CI.getName());
return BinaryOperator::CreateAShr(I, ShAmtV);
}
BA == CA && A->getType() == CI.getType()) {
unsigned MidSize = Src->getType()->getScalarSizeInBits();
unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
A = Builder->CreateShl(A, ShAmtV, CI.getName());
return BinaryOperator::CreateAShr(A, ShAmtV);
}
return 0;