[llvm] [InstCombine] Preserve nuw in canonicalizeGEPOfConstGEPI8() (PR #151533)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 31 08:12:58 PDT 2025
https://github.com/nikic updated https://github.com/llvm/llvm-project/pull/151533
>From d1497fee26038be968094b19c143c3fd10ee9065 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Thu, 31 Jul 2025 16:59:41 +0200
Subject: [PATCH 1/2] [InstCombine] Preserve nuw in
canonicalizeGEPOfConstGEPI8()
Proof: https://alive2.llvm.org/ce/z/vC239S
---
.../InstCombine/InstructionCombining.cpp | 10 ++-
.../Transforms/InstCombine/gepofconstgepi8.ll | 75 +++++++++++++++++++
2 files changed, 83 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 9e333202fb2e7..d5896a3041ff6 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2652,9 +2652,15 @@ static Instruction *canonicalizeGEPOfConstGEPI8(GetElementPtrInst &GEP,
APInt NewOffset = TypeSize * *C2 + *C1;
if (NewOffset.isZero() ||
(Src->hasOneUse() && GEP.getOperand(1)->hasOneUse())) {
+ GEPNoWrapFlags Flags = GEPNoWrapFlags::none();
+ if (GEP.hasNoUnsignedWrap() &&
+ cast<GEPOperator>(Src)->hasNoUnsignedWrap() &&
+ match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value())))
+ Flags |= GEPNoWrapFlags::noUnsignedWrap();
+
Value *GEPConst =
- IC.Builder.CreatePtrAdd(Base, IC.Builder.getInt(NewOffset));
- return GetElementPtrInst::Create(BaseType, GEPConst, VarIndex);
+ IC.Builder.CreatePtrAdd(Base, IC.Builder.getInt(NewOffset), "", Flags);
+ return GetElementPtrInst::Create(BaseType, GEPConst, VarIndex, Flags);
}
return nullptr;
diff --git a/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll b/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
index a92e0c263d357..63553189cca11 100644
--- a/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
+++ b/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
@@ -293,3 +293,78 @@ entry:
%p2 = getelementptr <vscale x 4 x i32>, ptr %p1, i64 %index
ret ptr %p2
}
+
+define ptr @test_all_nuw(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_nuw(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_partial_nuw1(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_partial_nuw1(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_partial_nuw2(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_partial_nuw2(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nuw i8, ptr %base, i64 1
+ %index = add i64 %a, 2
+ %p2 = getelementptr nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_partial_nuw3(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_partial_nuw3(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_nuw_disjoint(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_nuw_disjoint(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nuw i8, ptr %base, i64 1
+ %index = or disjoint i64 %a, 2
+ %p2 = getelementptr nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
>From 6a5906dae2cd7170d8928c4725c53116d126b7fd Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Thu, 31 Jul 2025 17:12:37 +0200
Subject: [PATCH 2/2] handle inbounds
---
.../InstCombine/InstructionCombining.cpp | 5 +-
.../Transforms/InstCombine/gepofconstgepi8.ll | 105 ++++++++++++++++++
2 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index d5896a3041ff6..0258f0a90ea76 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2655,8 +2655,11 @@ static Instruction *canonicalizeGEPOfConstGEPI8(GetElementPtrInst &GEP,
GEPNoWrapFlags Flags = GEPNoWrapFlags::none();
if (GEP.hasNoUnsignedWrap() &&
cast<GEPOperator>(Src)->hasNoUnsignedWrap() &&
- match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value())))
+ match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value()))) {
Flags |= GEPNoWrapFlags::noUnsignedWrap();
+ if (GEP.isInBounds() && cast<GEPOperator>(Src)->isInBounds())
+ Flags |= GEPNoWrapFlags::inBounds();
+ }
Value *GEPConst =
IC.Builder.CreatePtrAdd(Base, IC.Builder.getInt(NewOffset), "", Flags);
diff --git a/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll b/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
index 63553189cca11..e2f22b8322d2b 100644
--- a/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
+++ b/llvm/test/Transforms/InstCombine/gepofconstgepi8.ll
@@ -368,3 +368,108 @@ entry:
%p2 = getelementptr nuw i32, ptr %p1, i64 %index
ret ptr %p2
}
+
+define ptr @test_all_inbounds_nuw(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_inbounds_nuw(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr inbounds nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr inbounds nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr inbounds nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_partial_inbounds1(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_partial_inbounds1(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr inbounds nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_partial_inbounds2(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_partial_inbounds2(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr inbounds nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_inbounds_partial_nuw1(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_inbounds_partial_nuw1(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 7
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr inbounds i8, ptr %base, i64 -1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr inbounds nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_inbounds_partial_nuw2(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_inbounds_partial_nuw2(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr inbounds nuw i8, ptr %base, i64 1
+ %index = add nuw i64 %a, 2
+ %p2 = getelementptr inbounds i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_inbounds_partial_nuw3(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_inbounds_partial_nuw3(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr inbounds nuw i8, ptr %base, i64 1
+ %index = add i64 %a, 2
+ %p2 = getelementptr inbounds nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
+
+define ptr @test_all_nusw_nuw(ptr %base, i64 %a) {
+; CHECK-LABEL: define ptr @test_all_nusw_nuw(
+; CHECK-SAME: ptr [[BASE:%.*]], i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = getelementptr nuw i8, ptr [[BASE]], i64 9
+; CHECK-NEXT: [[P2:%.*]] = getelementptr nuw i32, ptr [[TMP0]], i64 [[A]]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+entry:
+ %p1 = getelementptr nusw nuw i8, ptr %base, i64 1
+ %index = add nsw nuw i64 %a, 2
+ %p2 = getelementptr nusw nuw i32, ptr %p1, i64 %index
+ ret ptr %p2
+}
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