[InstCombine] Check no wrap flags before folding icmp of GEPs with same indices #121628
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@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesAlive2: https://alive2.llvm.org/ce/z/Dr3Sbe Full diff: https://github.com/llvm/llvm-project/pull/121628.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index d6fdade25559fe..8b23583c510637 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -747,6 +747,8 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
ConstantExpr::getPointerBitCastOrAddrSpaceCast(
cast<Constant>(RHS), Base->getType()));
} else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
+ GEPNoWrapFlags NW = GEPLHS->getNoWrapFlags() & GEPRHS->getNoWrapFlags();
+
// If the base pointers are different, but the indices are the same, just
// compare the base pointer.
if (PtrBase != GEPRHS->getOperand(0)) {
@@ -764,7 +766,8 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
// If all indices are the same, just compare the base pointers.
Type *BaseType = GEPLHS->getOperand(0)->getType();
- if (IndicesTheSame && CmpInst::makeCmpResultType(BaseType) == I.getType())
+ if (IndicesTheSame &&
+ CmpInst::makeCmpResultType(BaseType) == I.getType() && CanFold(NW))
return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
// If we're comparing GEPs with two base pointers that only differ in type
@@ -804,7 +807,6 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
return transformToIndexedCompare(GEPLHS, RHS, Cond, DL, *this);
}
- GEPNoWrapFlags NW = GEPLHS->getNoWrapFlags() & GEPRHS->getNoWrapFlags();
if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands() &&
GEPLHS->getSourceElementType() == GEPRHS->getSourceElementType()) {
// If the GEPs only differ by one index, compare it.
diff --git a/llvm/test/Transforms/InstCombine/icmp-gep.ll b/llvm/test/Transforms/InstCombine/icmp-gep.ll
index f9b90c224d8327..7f8f1ae73948d1 100644
--- a/llvm/test/Transforms/InstCombine/icmp-gep.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-gep.ll
@@ -709,3 +709,51 @@ define i1 @pointer_icmp_aligned_with_offset_negative(ptr align 8 %a, ptr align 8
%cmp = icmp eq ptr %gep, %a2
ret i1 %cmp
}
+
+define i1 @gep_diff_base_same_indices(ptr %x, ptr %y, i64 %z) {
+; CHECK-LABEL: @gep_diff_base_same_indices(
+; CHECK-NEXT: [[X:%.*]] = getelementptr i8, ptr [[X1:%.*]], i64 [[Z:%.*]]
+; CHECK-NEXT: [[Y:%.*]] = getelementptr i8, ptr [[Y1:%.*]], i64 [[Z]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[X]], [[Y]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %gep1 = getelementptr i8, ptr %x, i64 %z
+ %gep2 = getelementptr i8, ptr %y, i64 %z
+ %cmp = icmp ult ptr %gep1, %gep2
+ ret i1 %cmp
+}
+
+define i1 @gep_diff_base_same_indices_nuw(ptr %x, ptr %y, i64 %z) {
+; CHECK-LABEL: @gep_diff_base_same_indices_nuw(
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %gep1 = getelementptr nuw i8, ptr %x, i64 %z
+ %gep2 = getelementptr nuw i8, ptr %y, i64 %z
+ %cmp = icmp ult ptr %gep1, %gep2
+ ret i1 %cmp
+}
+
+define i1 @gep_diff_base_same_indices_nusw(ptr %x, ptr %y, i64 %z) {
+; CHECK-LABEL: @gep_diff_base_same_indices_nusw(
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %gep1 = getelementptr nusw i8, ptr %x, i64 %z
+ %gep2 = getelementptr nusw i8, ptr %y, i64 %z
+ %cmp = icmp ult ptr %gep1, %gep2
+ ret i1 %cmp
+}
+
+define i1 @gep_diff_base_same_indices_nuw_nusw(ptr %x, ptr %y, i64 %z) {
+; CHECK-LABEL: @gep_diff_base_same_indices_nuw_nusw(
+; CHECK-NEXT: [[X:%.*]] = getelementptr nuw i8, ptr [[X1:%.*]], i64 [[Z:%.*]]
+; CHECK-NEXT: [[Y:%.*]] = getelementptr nusw i8, ptr [[Y1:%.*]], i64 [[Z]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[X]], [[Y]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %gep1 = getelementptr nuw i8, ptr %x, i64 %z
+ %gep2 = getelementptr nusw i8, ptr %y, i64 %z
+ %cmp = icmp ult ptr %gep1, %gep2
+ ret i1 %cmp
+}
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Collaborator
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/198/builds/812 Here is the relevant piece of the build log for the reference |
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Alive2: https://alive2.llvm.org/ce/z/Dr3Sbe
Closes #121581.