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[InstCombine] Generalize sub of selects optimization to all BinaryOperators

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This exposes further optimization opportunities if the selects are
correlated.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242235 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2015-07-14 22:39:23 +00:00
parent d640af829c
commit 137ad1ded9
3 changed files with 37 additions and 26 deletions
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26
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@@ -1611,32 +1611,6 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
return BinaryOperator::CreateAnd(A, B);
}
// (sub (select (a, c, b)), (select (a, d, b))) -> (select (a, (sub c, d), 0))
// (sub (select (a, b, c)), (select (a, b, d))) -> (select (a, 0, (sub c, d)))
if (auto *SI0 = dyn_cast<SelectInst>(Op0)) {
if (auto *SI1 = dyn_cast<SelectInst>(Op1)) {
if (SI0->getCondition() == SI1->getCondition()) {
if (Value *V = SimplifySubInst(
SI0->getFalseValue(), SI1->getFalseValue(), I.hasNoSignedWrap(),
I.hasNoUnsignedWrap(), DL, TLI, DT, AC))
return SelectInst::Create(
SI0->getCondition(),
Builder->CreateSub(SI0->getTrueValue(), SI1->getTrueValue(), "",
/*HasNUW=*/I.hasNoUnsignedWrap(),
/*HasNSW=*/I.hasNoSignedWrap()),
V);
if (Value *V = SimplifySubInst(SI0->getTrueValue(), SI1->getTrueValue(),
I.hasNoSignedWrap(),
I.hasNoUnsignedWrap(), DL, TLI, DT, AC))
return SelectInst::Create(
SI0->getCondition(), V,
Builder->CreateSub(SI0->getFalseValue(), SI1->getFalseValue(), "",
/*HasNUW=*/I.hasNoUnsignedWrap(),
/*HasNSW=*/I.hasNoSignedWrap()));
}
}
}
if (Op0->hasOneUse()) {
Value *Y = nullptr;
// ((X | Y) - X) --> (~X & Y)