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[ConstraintElim] Apply add with neg constant first during decomp. #164791

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Merged
fhahn merged 1 commit into from
Oct 23, 2025
Merged

[ConstraintElim] Apply add with neg constant first during decomp. #164791

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20 changes: 10 additions & 10 deletions llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -614,6 +614,16 @@ static Decomposition decompose(Value *V,
return {V, IsKnownNonNegative};
}

if (match(V, m_Add(m_Value(Op0), m_ConstantInt(CI))) && CI->isNegative() &&
canUseSExt(CI)) {
Preconditions.emplace_back(
CmpInst::ICMP_UGE, Op0,
ConstantInt::get(Op0->getType(), CI->getSExtValue() * -1));
if (auto Decomp = MergeResults(Op0, CI, true))
return *Decomp;
return {V, IsKnownNonNegative};
}

if (match(V, m_NSWAdd(m_Value(Op0), m_Value(Op1)))) {
if (!isKnownNonNegative(Op0, DL))
Preconditions.emplace_back(CmpInst::ICMP_SGE, Op0,
Expand All @@ -627,16 +637,6 @@ static Decomposition decompose(Value *V,
return {V, IsKnownNonNegative};
}

if (match(V, m_Add(m_Value(Op0), m_ConstantInt(CI))) && CI->isNegative() &&
canUseSExt(CI)) {
Preconditions.emplace_back(
CmpInst::ICMP_UGE, Op0,
ConstantInt::get(Op0->getType(), CI->getSExtValue() * -1));
if (auto Decomp = MergeResults(Op0, CI, true))
return *Decomp;
return {V, IsKnownNonNegative};
}

// Decompose or as an add if there are no common bits between the operands.
if (match(V, m_DisjointOr(m_Value(Op0), m_ConstantInt(CI)))) {
if (auto Decomp = MergeResults(Op0, CI, IsSigned))
Expand Down
6 changes: 2 additions & 4 deletions llvm/test/Transforms/ConstraintElimination/add-nsw.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -757,8 +757,7 @@ define i1 @add_neg_1_known_sge_ult_1(i32 %a) {
; CHECK-NEXT: [[A_SGE:%.*]] = icmp sge i32 [[A:%.*]], 1
; CHECK-NEXT: call void @llvm.assume(i1 [[A_SGE]])
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[A]], -1
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[SUB]], [[A]]
; CHECK-NEXT: ret i1 [[C]]
; CHECK-NEXT: ret i1 true
;
entry:
%a.sge = icmp sge i32 %a, 1
Expand Down Expand Up @@ -823,8 +822,7 @@ define i1 @add_neg_3_known_sge_ult_1(i32 %a) {
; CHECK-NEXT: [[A_SGE:%.*]] = icmp sge i32 [[A:%.*]], 3
; CHECK-NEXT: call void @llvm.assume(i1 [[A_SGE]])
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[A]], -3
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[SUB]], [[A]]
; CHECK-NEXT: ret i1 [[C]]
; CHECK-NEXT: ret i1 true
;
entry:
%a.sge = icmp sge i32 %a, 3
Expand Down
6 changes: 2 additions & 4 deletions llvm/test/Transforms/ConstraintElimination/gep-arithmetic-add.ll
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Expand Up @@ -389,8 +389,7 @@ define i1 @gep_count_add_1_sge_known_ult_1(i32 %count, ptr %p) {
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[COUNT]], -1
; CHECK-NEXT: [[SUB_EXT:%.*]] = zext i32 [[SUB]] to i64
; CHECK-NEXT: [[GEP_SUB:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 [[SUB_EXT]]
; CHECK-NEXT: [[C:%.*]] = icmp ult ptr [[GEP_SUB]], [[GEP_COUNT]]
; CHECK-NEXT: ret i1 [[C]]
; CHECK-NEXT: ret i1 true
;
entry:
%sge = icmp sge i32 %count, 1
Expand All @@ -415,8 +414,7 @@ define i1 @gep_count_add_1_sge_known_uge_1(i32 %count, ptr %p) {
; CHECK-NEXT: [[SUB:%.*]] = add nsw i32 [[COUNT]], -1
; CHECK-NEXT: [[SUB_EXT:%.*]] = zext i32 [[SUB]] to i64
; CHECK-NEXT: [[GEP_SUB:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 [[SUB_EXT]]
; CHECK-NEXT: [[C:%.*]] = icmp uge ptr [[GEP_SUB]], [[P]]
; CHECK-NEXT: ret i1 [[C]]
; CHECK-NEXT: ret i1 true
;
entry:
%sge = icmp sge i32 %count, 1
Expand Down