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[InstCombine] use similar ops for related folds; NFCI 

It's less efficient to produce 'ule' than 'ult' since we know we're going to
canonicalize to 'ult', but we shouldn't have duplicated code for these folds.

As a trade-off, this was a pretty terrible way to make a '2'. :)
       if (LHSC == SubOne(RHSC)) 
         AddC = ConstantExpr::getSub(AddOne(RHSC), LHSC);

The next steps are to share the code to fix PR32524 and add the missing 'and'
fold that was left out when PR14708 was fixed:
https://bugs.llvm.org/show_bug.cgi?id=14708

llvm-svn: 300222
This commit is contained in:
Sanjay Patel 2017-04-13 17:36:24 +00:00
parent bdb8b58d16
commit 9745d24a66
1 changed files with 9 additions and 10 deletions
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19
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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@ -881,11 +881,11 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
// zero.
if (LHSC->getValue() == 0 && RHSC->getValue().isAllOnesValue())
std::swap(LHSC, RHSC);
if (LHSC == SubOne(RHSC)) { // (X != 13 & X != 14) -> X-13 >u 1
Constant *AddC = ConstantExpr::getNeg(LHSC);
Value *Add = Builder->CreateAdd(LHS0, AddC, LHS0->getName() + ".off");
return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1),
LHS0->getName() + ".cmp");
if (LHSC == SubOne(RHSC)) {
// (X != 13 & X != 14) -> X-13 >u 1
// An 'add' is the canonical IR form, so favor that over a 'sub'.
Value *Add = Builder->CreateAdd(LHS0, ConstantExpr::getNeg(LHSC));
return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1));
}
break; // (X != 13 & X != 15) -> no change
}
@ -1786,11 +1786,10 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
}
if (LHSC == SubOne(RHSC)) {
// (X == 13 | X == 14) -> X-13 <u 2
Constant *AddC = ConstantExpr::getNeg(LHSC);
Value *Add = Builder->CreateAdd(LHS0, AddC, LHS0->getName() + ".off");
AddC = ConstantExpr::getSub(AddOne(RHSC), LHSC);
return Builder->CreateICmpULT(Add, AddC);
// (X == 13 | X == 14) -> X-13 <=u 1
// An 'add' is the canonical IR form, so favor that over a 'sub'.
Value *Add = Builder->CreateAdd(LHS0, ConstantExpr::getNeg(LHSC));
return Builder->CreateICmpULE(Add, ConstantInt::get(Add->getType(), 1));
}
break; // (X == 13 | X == 15) -> no change