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[InstCombine] Negator: freeze is freely negatible if it's operand is negatible

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This commit is contained in:
Roman Lebedev 2020-08-23 22:53:05 +03:00
parent 324948b801
commit 6072801a3e
2 changed files with 10 additions and 3 deletions
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7
lib/Transforms/InstCombine/InstCombineNegator.cpp
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@ -244,6 +244,13 @@ LLVM_NODISCARD Value *Negator::visitImpl(Value *V, unsigned Depth) {
}
switch (I->getOpcode()) {
case Instruction::Freeze: {
// `freeze` is negatible if its operand is negatible.
Value *NegOp = negate(I->getOperand(0), Depth + 1);
if (!NegOp) // Early return.
return nullptr;
return Builder.CreateFreeze(NegOp, I->getName() + ".neg");
}
case Instruction::PHI: {
// `phi` is negatible if all the incoming values are negatible.
auto *PHI = cast<PHINode>(I);

6
test/Transforms/InstCombine/sub-of-negatible.ll
View File

@ -1214,9 +1214,9 @@ define i8 @dont_negate_ordinary_select(i8 %x, i8 %y, i8 %z, i1 %c) {
; Freeze is transparent as far as negation is concerned
define i4 @negate_freeze(i4 %x, i4 %y, i4 %z) {
; CHECK-LABEL: @negate_freeze(
; CHECK-NEXT: [[T0:%.*]] = sub i4 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[T1:%.*]] = freeze i4 [[T0]]
; CHECK-NEXT: [[T2:%.*]] = sub i4 [[Z:%.*]], [[T1]]
; CHECK-NEXT: [[T0_NEG:%.*]] = sub i4 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[T1_NEG:%.*]] = freeze i4 [[T0_NEG]]
; CHECK-NEXT: [[T2:%.*]] = add i4 [[T1_NEG]], [[Z:%.*]]
; CHECK-NEXT: ret i4 [[T2]]
;
%t0 = sub i4 %x, %y