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[InstCombine] Generalize sub of selects optimization to all BinaryOperators 

This exposes further optimization opportunities if the selects are
correlated.

llvm-svn: 242235
This commit is contained in:
David Majnemer 2015-07-14 22:39:23 +00:00
parent a97ad16538
commit 33b6f82e72
3 changed files with 37 additions and 26 deletions
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26
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -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)

27
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -623,6 +623,33 @@ Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) {
}
}
// (op (select (a, c, b)), (select (a, d, b))) -> (select (a, (op c, d), 0))
// (op (select (a, b, c)), (select (a, b, d))) -> (select (a, 0, (op c, d)))
if (auto *SI0 = dyn_cast<SelectInst>(LHS)) {
if (auto *SI1 = dyn_cast<SelectInst>(RHS)) {
if (SI0->getCondition() == SI1->getCondition()) {
Value *SI = nullptr;
if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getFalseValue(),
SI1->getFalseValue(), DL, TLI, DT, AC))
SI = Builder->CreateSelect(SI0->getCondition(),
Builder->CreateBinOp(TopLevelOpcode,
SI0->getTrueValue(),
SI1->getTrueValue()),
V);
if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getTrueValue(),
SI1->getTrueValue(), DL, TLI, DT, AC))
SI = Builder->CreateSelect(
SI0->getCondition(), V,
Builder->CreateBinOp(TopLevelOpcode, SI0->getFalseValue(),
SI1->getFalseValue()));
if (SI) {
SI->takeName(&I);
return SI;
}
}
}
}
return nullptr;
}

10
llvm/test/Transforms/InstCombine/add2.ll
View File

@ -395,3 +395,13 @@ define i8 @add_of_mul(i8 %x, i8 %y, i8 %z) {
%sum = add nsw i8 %mA, %mB
ret i8 %sum
}
define i32 @add_of_selects(i1 %A, i32 %B) {
%sel0 = select i1 %A, i32 0, i32 -2
%sel1 = select i1 %A, i32 %B, i32 2
%add = add i32 %sel0, %sel1
ret i32 %add
; CHECK-LABEL: @add_of_selects(
; CHECK-NEXT: %[[sel:.*]] = select i1 %A, i32 %B, i32 0
; CHECK-NEXT: ret i32 %[[sel]]
}