[llvm] [MoveAutoInit] Fix for miscompilation for #150120 (PR #173961)
Nimit Sachdeva via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 23 12:50:49 PST 2026
https://github.com/nimit25 updated https://github.com/llvm/llvm-project/pull/173961
>From a621c0890a9bc2cd16e69403293cdf48d79231f7 Mon Sep 17 00:00:00 2001
From: Nimit Sachdeva <nimsach at amazon.com>
Date: Tue, 30 Dec 2025 01:24:06 -0500
Subject: [PATCH 1/3] fix for miscompilation for #150120
---
llvm/lib/Transforms/Utils/MoveAutoInit.cpp | 3 +-
.../Transforms/MoveAutoInit/loop-store.ll | 57 +++++++++++++++++++
2 files changed, 59 insertions(+), 1 deletion(-)
create mode 100644 llvm/test/Transforms/MoveAutoInit/loop-store.ll
diff --git a/llvm/lib/Transforms/Utils/MoveAutoInit.cpp b/llvm/lib/Transforms/Utils/MoveAutoInit.cpp
index ad105f5a57b49..9302d5e284fd3 100644
--- a/llvm/lib/Transforms/Utils/MoveAutoInit.cpp
+++ b/llvm/lib/Transforms/Utils/MoveAutoInit.cpp
@@ -164,7 +164,8 @@ static bool runMoveAutoInit(Function &F, DominatorTree &DT, MemorySSA &MSSA) {
if (!DT.isReachableFromEntry(Pred))
continue;
-
+ if (!DT.dominates(Pred, UsersDominatorHead))
+ continue;
DominatingPredecessor =
DominatingPredecessor
? DT.findNearestCommonDominator(DominatingPredecessor, Pred)
diff --git a/llvm/test/Transforms/MoveAutoInit/loop-store.ll b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
new file mode 100644
index 0000000000000..8bd0913728db8
--- /dev/null
+++ b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes='move-auto-init' -verify-memoryssa -S < %s | FileCheck %s
+
+
+define i8 @test_no_update(i32 %a, i32 %b) {
+; CHECK-LABEL: define i8 @test_no_update
+; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT: lbl_653:
+; CHECK-NEXT: [[L_580:%.*]] = alloca i32, align 4
+; CHECK-NEXT: store i32 1, ptr [[L_580]], align 4
+; CHECK-NEXT: br i1 true, label [[LBL_629:%.*]], label [[IF_THEN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: br label [[IF_END:%.*]]
+; CHECK: lbl_629:
+; CHECK-NEXT: br label [[IF_END]]
+; CHECK: if.end:
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[L_580]], align 4
+; CHECK-NEXT: [[TOBOOL223_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[TOBOOL223_NOT]], label [[LOR_RHS224:%.*]], label [[LOR_END230:%.*]]
+; CHECK: lor.rhs224:
+; CHECK-NEXT: store i8 0, ptr null, align 1
+; CHECK-NEXT: br label [[LOR_END230]]
+; CHECK: lor.end230:
+; CHECK-NEXT: br i1 true, label [[FOR_INC456_1:%.*]], label [[LBL_629]]
+; CHECK: for.inc456.1:
+; CHECK-NEXT: ret i8 0
+;
+
+lbl_653:
+ %l_580 = alloca i32, align 4
+ store i32 1, ptr %l_580, align 4, !annotation !0
+ br i1 true, label %lbl_629, label %if.then
+
+if.then: ; preds = %lbl_653
+ br label %if.end
+
+lbl_629: ; preds = %lor.end230, %lbl_653
+ br label %if.end
+
+if.end: ; preds = %lbl_629, %if.then
+ %0 = load i32, ptr %l_580, align 4
+ %tobool223.not = icmp eq i32 %0, 0
+ br i1 %tobool223.not, label %lor.rhs224, label %lor.end230
+
+lor.rhs224: ; preds = %if.end
+ store i8 0, ptr null, align 1
+ br label %lor.end230
+
+lor.end230: ; preds = %lor.rhs224, %if.end
+ br i1 true, label %for.inc456.1, label %lbl_629
+
+for.inc456.1: ; preds = %lor.end230
+ ret i8 0
+}
+
+
+!0 = !{!"auto-init"}
\ No newline at end of file
>From 7d6acc66bab3394385370771f577ac0a352ac167 Mon Sep 17 00:00:00 2001
From: Nimit Sachdeva <nimsach at amazon.com>
Date: Fri, 9 Jan 2026 00:30:04 -0500
Subject: [PATCH 2/3] update test
---
llvm/test/Transforms/MoveAutoInit/loop-store.ll | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/llvm/test/Transforms/MoveAutoInit/loop-store.ll b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
index 8bd0913728db8..87aecad214cca 100644
--- a/llvm/test/Transforms/MoveAutoInit/loop-store.ll
+++ b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
@@ -18,7 +18,8 @@ define i8 @test_no_update(i32 %a, i32 %b) {
; CHECK-NEXT: [[TOBOOL223_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
; CHECK-NEXT: br i1 [[TOBOOL223_NOT]], label [[LOR_RHS224:%.*]], label [[LOR_END230:%.*]]
; CHECK: lor.rhs224:
-; CHECK-NEXT: store i8 0, ptr null, align 1
+; CHECK-NEXT: [[TMP:%.*]] = alloca i8, align 1
+; CHECK-NEXT: store i8 0, ptr [[TMP]], align 1
; CHECK-NEXT: br label [[LOR_END230]]
; CHECK: lor.end230:
; CHECK-NEXT: br i1 true, label [[FOR_INC456_1:%.*]], label [[LBL_629]]
@@ -43,7 +44,8 @@ if.end: ; preds = %lbl_629, %if.then
br i1 %tobool223.not, label %lor.rhs224, label %lor.end230
lor.rhs224: ; preds = %if.end
- store i8 0, ptr null, align 1
+ %tmp = alloca i8, align 1
+ store i8 0, ptr %tmp, align 1
br label %lor.end230
lor.end230: ; preds = %lor.rhs224, %if.end
@@ -54,4 +56,4 @@ for.inc456.1: ; preds = %lor.end230
}
-!0 = !{!"auto-init"}
\ No newline at end of file
+!0 = !{!"auto-init"}
>From 9eb5b6d7a4722e611e09b2c92ceb1ca0d21c4627 Mon Sep 17 00:00:00 2001
From: Nimit Sachdeva <nimsach at amazon.com>
Date: Thu, 22 Jan 2026 23:29:39 -0500
Subject: [PATCH 3/3] fix test
---
llvm/test/Transforms/MoveAutoInit/loop-store.ll | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/test/Transforms/MoveAutoInit/loop-store.ll b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
index 87aecad214cca..11c02120a92aa 100644
--- a/llvm/test/Transforms/MoveAutoInit/loop-store.ll
+++ b/llvm/test/Transforms/MoveAutoInit/loop-store.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
-; RUN: opt -passes='move-auto-init' -verify-memoryssa -S < %s | FileCheck %s
+; RUN: opt -passes=move-auto-init -S < %s | FileCheck %s
define i8 @test_no_update(i32 %a, i32 %b) {
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