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[InstCombine] Relax one-use requirement for add iN (sext i1 X), (sext i1 Y) --> sext (X | Y) to iN #90509

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Merged
merged 2 commits into from
Jun 28, 2024
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[InstCombine] Relax one-use requirement for add iN (sext i1 X), (sext i1 Y) --> sext (X | Y) to iN #90509

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d60bb01
[InstCombine] Pre-commit tests (NFC)
AZero13 May 2, 2024
03c8939
[InstCombine] Remove one-use requirement for add iN (sext i1 X), (sex…
AZero13 May 6, 2024
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8 changes: 4 additions & 4 deletions llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -499,10 +499,10 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
}

// add iN (sext i1 X), (sext i1 Y) --> sext (X | Y) to iN
// TODO: Relax the one-use checks because we are removing an instruction?
if (match(I, m_Add(m_OneUse(m_SExt(m_Value(X))),
m_OneUse(m_SExt(m_Value(Y))))) &&
X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType()) {
if (match(I, m_Add(m_SExt(m_Value(X)), m_SExt(m_Value(Y)))) &&
X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType() &&
(I->getOperand(0)->hasOneUse() || I->getOperand(1)->hasOneUse())) {

// Truth table for inputs and output signbits:
// X:0 | X:1
// -----------
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33 changes: 24 additions & 9 deletions llvm/test/Transforms/InstCombine/add.ll
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Expand Up @@ -1435,15 +1435,28 @@ define i32 @and31_add_sexts(i1 %x, i1 %y) {
ret i32 %r
}

; Negative test - extra use

define i32 @lshr_add_use_sexts(i1 %x, i1 %y, ptr %p) {
; CHECK-LABEL: @lshr_add_use_sexts(
; CHECK-NEXT: [[YS:%.*]] = sext i1 [[Y:%.*]] to i32
; CHECK-NEXT: store i32 [[YS]], ptr [[P:%.*]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = or i1 [[X:%.*]], [[Y]]
; CHECK-NEXT: [[R:%.*]] = zext i1 [[TMP1]] to i32
; CHECK-NEXT: ret i32 [[R]]
;
%xs = sext i1 %x to i32
%ys = sext i1 %y to i32
store i32 %ys, ptr %p
%sub = add i32 %xs, %ys
%r = lshr i32 %sub, 31
ret i32 %r
}

define i32 @lshr_add_use_sexts_2(i1 %x, i1 %y, ptr %p) {
; CHECK-LABEL: @lshr_add_use_sexts_2(
; CHECK-NEXT: [[XS:%.*]] = sext i1 [[X:%.*]] to i32
; CHECK-NEXT: store i32 [[XS]], ptr [[P:%.*]], align 4
; CHECK-NEXT: [[YS:%.*]] = sext i1 [[Y:%.*]] to i32
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[XS]], [[YS]]
; CHECK-NEXT: [[R:%.*]] = lshr i32 [[SUB]], 31
; CHECK-NEXT: [[TMP1:%.*]] = or i1 [[X]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = zext i1 [[TMP1]] to i32
; CHECK-NEXT: ret i32 [[R]]
;
%xs = sext i1 %x to i32
Expand All @@ -1456,18 +1469,20 @@ define i32 @lshr_add_use_sexts(i1 %x, i1 %y, ptr %p) {

; Negative test - extra use

define i32 @lshr_add_use2_sexts(i1 %x, i1 %y, ptr %p) {
; CHECK-LABEL: @lshr_add_use2_sexts(
declare void @use_sexts(i32, i32)

define i32 @lshr_add_use_sexts_both(i1 %x, i1 %y) {
; CHECK-LABEL: @lshr_add_use_sexts_both(
; CHECK-NEXT: [[XS:%.*]] = sext i1 [[X:%.*]] to i32
; CHECK-NEXT: [[YS:%.*]] = sext i1 [[Y:%.*]] to i32
; CHECK-NEXT: store i32 [[YS]], ptr [[P:%.*]], align 4
; CHECK-NEXT: call void @use_sexts(i32 [[XS]], i32 [[YS]])
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[XS]], [[YS]]
; CHECK-NEXT: [[R:%.*]] = lshr i32 [[SUB]], 31
; CHECK-NEXT: ret i32 [[R]]
;
%xs = sext i1 %x to i32
%ys = sext i1 %y to i32
store i32 %ys, ptr %p
call void @use_sexts(i32 %xs, i32 %ys)
%sub = add i32 %xs, %ys
%r = lshr i32 %sub, 31
ret i32 %r
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