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Recognize n != 0 ? n : 1 as umax(n, 1). Previously only ULT/UGT/ULE/UGE

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comparisons were recognized for umax, but instcombine canonicalizes
unsigned comparisons with zero to this simpler form.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73717 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-06-18 20:21:07 +00:00
parent 6cf69cfdee
commit 30fb512e95
1 changed files with 18 additions and 0 deletions
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18
lib/Analysis/ScalarEvolution.cpp
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@ -2580,6 +2580,24 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
return getNotSCEV(getUMaxExpr(getNotSCEV(getSCEV(LHS)),
getNotSCEV(getSCEV(RHS))));
break;
case ICmpInst::ICMP_NE:
// n != 0 ? n : 1 -> umax(n, 1)
if (LHS == U->getOperand(1) &&
isa<ConstantInt>(U->getOperand(2)) &&
cast<ConstantInt>(U->getOperand(2))->isOne() &&
isa<ConstantInt>(RHS) &&
cast<ConstantInt>(RHS)->isZero())
return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(2)));
break;
case ICmpInst::ICMP_EQ:
// n == 0 ? 1 : n -> umax(n, 1)
if (LHS == U->getOperand(2) &&
isa<ConstantInt>(U->getOperand(1)) &&
cast<ConstantInt>(U->getOperand(1))->isOne() &&
isa<ConstantInt>(RHS) &&
cast<ConstantInt>(RHS)->isZero())
return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(1)));
break;
default:
break;
}