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[InstCombine] Fold (icmp eq/ne (add nuw x, y), 0) -> (icmp eq/ne (or x, y), 0) #88088

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[InstCombine] Fold (icmp eq/ne (add nuw x, y), 0) -> (icmp eq/ne (or x, y), 0) #88088

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98bfa63
[InstCombine] Add tests for folding `(icmp eq/ne (add nuw x, y), 0)`;…
goldsteinn Apr 7, 2024
08ea7f3
[InstCombine] Fold `(icmp eq/ne (add nuw x, y), 0)` -> `(icmp eq/ne (…
goldsteinn Apr 7, 2024
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5 changes: 5 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3453,6 +3453,11 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
if (Value *NegVal = dyn_castNegVal(BOp0))
return new ICmpInst(Pred, NegVal, BOp1);
if (BO->hasOneUse()) {
// (add nuw A, B) != 0 -> (or A, B) != 0
if (match(BO, m_NUWAdd(m_Value(), m_Value()))) {
Value *Or = Builder.CreateOr(BOp0, BOp1);
return new ICmpInst(Pred, Or, Constant::getNullValue(BO->getType()));
}
Value *Neg = Builder.CreateNeg(BOp1);
Neg->takeName(BO);
return new ICmpInst(Pred, BOp0, Neg);
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36 changes: 28 additions & 8 deletions llvm/test/Transforms/InstCombine/icmp-add.ll
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Expand Up @@ -9,10 +9,8 @@ declare void @use(i32)
define i1 @cvt_icmp_0_zext_plus_zext_eq_i16(i16 %arg, i16 %arg1) {
; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i16(
; CHECK-NEXT: bb:
; CHECK-NEXT: [[I:%.*]] = zext i16 [[ARG:%.*]] to i32
; CHECK-NEXT: [[I2:%.*]] = zext i16 [[ARG1:%.*]] to i32
; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]]
; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]]
; CHECK-NEXT: [[TMP0:%.*]] = or i16 [[ARG1:%.*]], [[ARG:%.*]]
; CHECK-NEXT: [[I4:%.*]] = icmp eq i16 [[TMP0]], 0
; CHECK-NEXT: ret i1 [[I4]]
;
bb:
Expand All @@ -27,10 +25,8 @@ bb:
define i1 @cvt_icmp_0_zext_plus_zext_eq_i8(i8 %arg, i8 %arg1) {
; CHECK-LABEL: @cvt_icmp_0_zext_plus_zext_eq_i8(
; CHECK-NEXT: bb:
; CHECK-NEXT: [[I:%.*]] = zext i8 [[ARG:%.*]] to i32
; CHECK-NEXT: [[I2:%.*]] = zext i8 [[ARG1:%.*]] to i32
; CHECK-NEXT: [[I3:%.*]] = sub nsw i32 0, [[I]]
; CHECK-NEXT: [[I4:%.*]] = icmp eq i32 [[I2]], [[I3]]
; CHECK-NEXT: [[TMP0:%.*]] = or i8 [[ARG1:%.*]], [[ARG:%.*]]
; CHECK-NEXT: [[I4:%.*]] = icmp eq i8 [[TMP0]], 0
; CHECK-NEXT: ret i1 [[I4]]
;
bb:
Expand Down Expand Up @@ -3003,4 +2999,28 @@ define i1 @icmp_dec_notnonzero(i8 %x) {
ret i1 %c
}

define i1 @icmp_addnuw_nonzero(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_addnuw_nonzero(
; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[TMP1]], 0
; CHECK-NEXT: ret i1 [[C]]
;
%i = add nuw i8 %x, %y
%c = icmp eq i8 %i, 0
ret i1 %c
}

define i1 @icmp_addnuw_nonzero_fail_multiuse(i32 %x, i32 %y) {
; CHECK-LABEL: @icmp_addnuw_nonzero_fail_multiuse(
; CHECK-NEXT: [[I:%.*]] = add nuw i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[I]], 0
; CHECK-NEXT: call void @use(i32 [[I]])
; CHECK-NEXT: ret i1 [[C]]
;
%i = add nuw i32 %x, %y
%c = icmp eq i32 %i, 0
call void @use(i32 %i)
ret i1 %c
}

declare void @llvm.assume(i1)
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