[llvm] [InstCombine] Check no wrap flags before folding icmp of GEPs with same indices (PR #121628)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 3 23:57:05 PST 2025
https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/121628
Alive2: https://alive2.llvm.org/ce/z/Dr3Sbe
Closes https://github.com/llvm/llvm-project/issues/121581.
>From 7460133d4ac20f1312b5f329b9042067b1d75678 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 4 Jan 2025 15:27:40 +0800
Subject: [PATCH 1/2] [InstCombine] Add pre-commit tests. NFC.
---
llvm/test/Transforms/InstCombine/icmp-gep.ll | 44 ++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/icmp-gep.ll b/llvm/test/Transforms/InstCombine/icmp-gep.ll
index f9b90c224d8327..3dfd0eddb1bdec 100644
--- a/llvm/test/Transforms/InstCombine/icmp-gep.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-gep.ll
@@ -709,3 +709,47 @@ 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: [[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: [[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
+}
>From b9c6d692bb43c8ad6f1f12ce6b2a09cf32d4e07f Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 4 Jan 2025 15:55:41 +0800
Subject: [PATCH 2/2] [InstCombine] Check no wrap flags before folding icmp of
GEPs with same indices
---
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 6 ++++--
llvm/test/Transforms/InstCombine/icmp-gep.ll | 8 ++++++--
2 files changed, 10 insertions(+), 4 deletions(-)
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 3dfd0eddb1bdec..7f8f1ae73948d1 100644
--- a/llvm/test/Transforms/InstCombine/icmp-gep.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-gep.ll
@@ -712,7 +712,9 @@ define i1 @pointer_icmp_aligned_with_offset_negative(ptr align 8 %a, ptr align 8
define i1 @gep_diff_base_same_indices(ptr %x, ptr %y, i64 %z) {
; CHECK-LABEL: @gep_diff_base_same_indices(
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[X:%.*]], [[Y:%.*]]
+; 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
@@ -745,7 +747,9 @@ define i1 @gep_diff_base_same_indices_nusw(ptr %x, ptr %y, i64 %z) {
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: [[CMP:%.*]] = icmp ult ptr [[X:%.*]], [[Y:%.*]]
+; 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
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