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release/20.x: [InstCombine] Check nowrap flags when folding comparison of GEPs with the same base pointer (#121892) #125858

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Merged
merged 1 commit into from
Feb 11, 2025
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release/20.x: [InstCombine] Check nowrap flags when folding comparison of GEPs with the same base pointer (#121892) #125858

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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -834,7 +834,7 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
return replaceInstUsesWith(I, // No comparison is needed here.
ConstantInt::get(I.getType(), ICmpInst::isTrueWhenEqual(Cond)));

else if (NumDifferences == 1 && CanFold(NW)) {
else if (NumDifferences == 1 && NW != GEPNoWrapFlags::none()) {
Value *LHSV = GEPLHS->getOperand(DiffOperand);
Value *RHSV = GEPRHS->getOperand(DiffOperand);
return NewICmp(NW, LHSV, RHSV);
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35 changes: 35 additions & 0 deletions llvm/test/Transforms/InstCombine/opaque-ptr.ll
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Expand Up @@ -467,6 +467,41 @@ define i1 @cmp_gep_same_base_same_type(ptr %ptr, i64 %idx1, i64 %idx2) {
ret i1 %cmp
}

define i1 @cmp_gep_same_base_same_type_maywrap(ptr %ptr, i64 %idx1, i64 %idx2) {
; CHECK-LABEL: @cmp_gep_same_base_same_type_maywrap(
; CHECK-NEXT: [[CMP_UNSHIFTED:%.*]] = xor i64 [[IDX1:%.*]], [[IDX2:%.*]]
; CHECK-NEXT: [[CMP_MASK:%.*]] = and i64 [[CMP_UNSHIFTED]], 4611686018427387903
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[CMP_MASK]], 0
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep1 = getelementptr i32, ptr %ptr, i64 %idx1
%gep2 = getelementptr i32, ptr %ptr, i64 %idx2
%cmp = icmp eq ptr %gep1, %gep2
ret i1 %cmp
}

define i1 @cmp_gep_same_base_same_type_nuw(ptr %ptr, i64 %idx1, i64 %idx2) {
; CHECK-LABEL: @cmp_gep_same_base_same_type_nuw(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[IDX1:%.*]], [[IDX2:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep1 = getelementptr nuw i32, ptr %ptr, i64 %idx1
%gep2 = getelementptr nuw i32, ptr %ptr, i64 %idx2
%cmp = icmp eq ptr %gep1, %gep2
ret i1 %cmp
}

define i1 @cmp_gep_same_base_same_type_nusw(ptr %ptr, i64 %idx1, i64 %idx2) {
; CHECK-LABEL: @cmp_gep_same_base_same_type_nusw(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[IDX1:%.*]], [[IDX2:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep1 = getelementptr nusw i32, ptr %ptr, i64 %idx1
%gep2 = getelementptr nusw i32, ptr %ptr, i64 %idx2
%cmp = icmp eq ptr %gep1, %gep2
ret i1 %cmp
}

define i1 @cmp_gep_same_base_different_type(ptr %ptr, i64 %idx1, i64 %idx2) {
; CHECK-LABEL: @cmp_gep_same_base_different_type(
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[IDX1:%.*]], 2
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