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[InstCombine] Further relax one-use constraint in foldICmpBinOp #122266

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[InstCombine] Further relax one-use constraint in foldICmpBinOp #122266

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a7a5d25
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Jan 9, 2025
116df20
[InstCombine] Further relax one-use constraint in `foldICmpBinOp`
dtcxzyw Jan 9, 2025
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4 changes: 2 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5435,7 +5435,6 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
}

if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() &&
(BO0->hasOneUse() || BO1->hasOneUse()) &&
BO0->getOperand(1) == BO1->getOperand(1)) {
switch (BO0->getOpcode()) {
default:
Expand Down Expand Up @@ -5468,7 +5467,8 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
break;

const APInt *C;
if (match(BO0->getOperand(1), m_APInt(C)) && !C->isZero() &&
if (BO0->hasOneUse() && BO1->hasOneUse() &&
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@goldsteinn goldsteinn Jan 9, 2025

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Should it be ||?

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@dtcxzyw dtcxzyw Jan 10, 2025

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No. We create two and instructions and one icmp here. See the test eq_mul_constants_with_tz_extra_use1.

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@goldsteinn goldsteinn Jan 10, 2025

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Yeah fair enough, just this case is not relaxing the constraint, its tightening it.

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@dtcxzyw dtcxzyw Jan 11, 2025

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Yes. I already pointed out this in the PR description.

match(BO0->getOperand(1), m_APInt(C)) && !C->isZero() &&
!C->isOne()) {
// icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
// Mask = -1 >> count-trailing-zeros(C).
Expand Down
33 changes: 33 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-mul.ll
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Expand Up @@ -3,6 +3,7 @@

declare void @llvm.assume(i1)
declare void @use(i8)
declare void @use32(i32)
declare void @usev2xi8(<2 x i8>)


Expand Down Expand Up @@ -780,6 +781,38 @@ define i1 @eq_mul_constants_with_tz(i32 %x, i32 %y) {
ret i1 %C
}

define i1 @eq_mul_constants_with_tz_extra_use1(i32 %x, i32 %y) {
; CHECK-LABEL: @eq_mul_constants_with_tz_extra_use1(
; CHECK-NEXT: [[A:%.*]] = mul i32 [[X:%.*]], 12
; CHECK-NEXT: call void @use32(i32 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul i32 [[Y:%.*]], 12
; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[A]], [[B]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul i32 %x, 12
call void @use32(i32 %A)
%B = mul i32 %y, 12
%C = icmp ne i32 %A, %B
ret i1 %C
}

define i1 @eq_mul_constants_with_tz_extra_use2(i32 %x, i32 %y) {
; CHECK-LABEL: @eq_mul_constants_with_tz_extra_use2(
; CHECK-NEXT: [[A:%.*]] = mul i32 [[X:%.*]], 12
; CHECK-NEXT: call void @use32(i32 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul i32 [[Y:%.*]], 12
; CHECK-NEXT: call void @use32(i32 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[A]], [[B]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul i32 %x, 12
call void @use32(i32 %A)
%B = mul i32 %y, 12
call void @use32(i32 %B)
%C = icmp ne i32 %A, %B
ret i1 %C
}

define <2 x i1> @eq_mul_constants_with_tz_splat(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @eq_mul_constants_with_tz_splat(
; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i32> [[X:%.*]], [[Y:%.*]]
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/InstCombine/icmp.ll
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Expand Up @@ -849,7 +849,7 @@ define i1 @test46_multiuse3(i32 %X, i32 %Y, i32 %Z) {
; CHECK-NEXT: call void @use_i32(i32 [[A]])
; CHECK-NEXT: [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: call void @use_i32(i32 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = ashr exact i32 %X, %Z
Expand Down
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