[llvm] [MergeFuncs] Don't introduce calls to weak_odr functions. (PR #125050)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 30 08:06:40 PST 2025
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/125050
>From 9418e749892df8cd4fa98f795b2bc09d5b101378 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 30 Jan 2025 11:32:06 +0000
Subject: [PATCH 1/3] [MergeFunc] Add tests for merging weak_odr functions.
---
.../Transforms/MergeFunc/merge-weak-odr.ll | 100 ++++++++++++++++++
1 file changed, 100 insertions(+)
create mode 100644 llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
diff --git a/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll b/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
new file mode 100644
index 000000000000000..6afa14c7ec439fa
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
@@ -0,0 +1,100 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs --version 5
+; RUN: opt -p mergefunc -S %s | FileCheck %s
+
+define weak_odr hidden void @weak_odr_caller_of_foo_1(ptr %p) {
+entry:
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ ret void
+}
+
+define weak_odr hidden void @weak_odr_caller_of_foo_2(ptr %p) {
+entry:
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ ret void
+}
+
+declare void @foo(ptr)
+
+define hidden void @weak_odr_caller_of_bar_1(ptr %p) {
+entry:
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ ret void
+}
+
+define weak_odr hidden void @non_weak_caller_of_bar_2(ptr %p) {
+entry:
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ ret void
+}
+
+declare void @bar(ptr)
+
+define hidden void @non_weak_caller_of_zar_1(ptr %p) {
+entry:
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ ret void
+}
+
+define weak_odr hidden void @weak_odr_caller_of_zar_2(ptr %p) {
+entry:
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ ret void
+}
+
+declare void @zar(ptr)
+; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_foo_1(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define weak_odr hidden void @non_weak_caller_of_bar_2(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define hidden void @non_weak_caller_of_zar_1(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_foo_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @weak_odr_caller_of_foo_1(ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define hidden void @weak_odr_caller_of_bar_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @non_weak_caller_of_bar_2(ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_zar_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @non_weak_caller_of_zar_1(ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
>From c20f3dd679d8d04d92b318c2a3df1d230a226ff2 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 30 Jan 2025 11:33:12 +0000
Subject: [PATCH 2/3] [MergeFuncs] Don't introduce calls to weak_odr functions.
Avoid creating new calls to weak_odr functions when merging 2 functions.
Consider 2 functions below, both present in 2 modules. Without this
patch, MergeFuncs in the first module may optimize A to call B and in
the second module B to call A.
Note that the 2 optimizations are vaild in isolation, but the linker then
could pick A from module 1 (which calls B) and B from module 2 which
calls A, introducing an infinte call cycle.
There may be other linkage types we need to be more careful about as
well.
define weak_odr hidden void @"A"(ptr %p) {
entry:
tail call void @"foo"(ptr %p)
ret void
}
define weak_odr hidden void @"B"(ptr %p) {
entry:
tail call void @"foo"(ptr %p)
ret void
}
---
llvm/lib/Transforms/IPO/MergeFunctions.cpp | 4 ++--
.../Transforms/MergeFunc/merge-weak-odr.ll | 20 +++++++++++++++----
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Transforms/IPO/MergeFunctions.cpp b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
index e8508416f542754..d991ec64445ee99 100644
--- a/llvm/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
@@ -891,8 +891,8 @@ bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
// Merge two equivalent functions. Upon completion, Function G is deleted.
void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
- if (F->isInterposable()) {
- assert(G->isInterposable());
+ if (F->isInterposable() || G->hasWeakODRLinkage()) {
+ assert(G->isInterposable() || G->hasWeakODRLinkage());
// Both writeThunkOrAlias() calls below must succeed, either because we can
// create aliases for G and NewF, or because a thunk for F is profitable.
diff --git a/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll b/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
index 6afa14c7ec439fa..d2e89092b9a8266 100644
--- a/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
+++ b/llvm/test/Transforms/MergeFunc/merge-weak-odr.ll
@@ -54,7 +54,7 @@ entry:
}
declare void @zar(ptr)
-; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_foo_1(
+; CHECK-LABEL: define private void @0(
; CHECK-SAME: ptr [[P:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: tail call void @foo(ptr [[P]])
@@ -72,7 +72,7 @@ declare void @zar(ptr)
; CHECK-NEXT: ret void
;
;
-; CHECK-LABEL: define hidden void @non_weak_caller_of_zar_1(
+; CHECK-LABEL: define private void @1(
; CHECK-SAME: ptr [[P:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: tail call void @zar(ptr [[P]])
@@ -83,7 +83,13 @@ declare void @zar(ptr)
;
; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_foo_2(
; CHECK-SAME: ptr [[TMP0:%.*]]) {
-; CHECK-NEXT: tail call void @weak_odr_caller_of_foo_1(ptr [[TMP0]])
+; CHECK-NEXT: tail call void @[[GLOB0:[0-9]+]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_foo_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB0]](ptr [[TMP0]])
; CHECK-NEXT: ret void
;
;
@@ -95,6 +101,12 @@ declare void @zar(ptr)
;
; CHECK-LABEL: define weak_odr hidden void @weak_odr_caller_of_zar_2(
; CHECK-SAME: ptr [[TMP0:%.*]]) {
-; CHECK-NEXT: tail call void @non_weak_caller_of_zar_1(ptr [[TMP0]])
+; CHECK-NEXT: tail call void @[[GLOB1:[0-9]+]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define hidden void @non_weak_caller_of_zar_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB1]](ptr [[TMP0]])
; CHECK-NEXT: ret void
;
>From ad402537682a67e74bf508c8032b653a6d9579ca Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 30 Jan 2025 16:06:02 +0000
Subject: [PATCH 3/3] !fixup also include linkonce_odr
---
llvm/lib/Transforms/IPO/MergeFunctions.cpp | 4 +-
llvm/test/Transforms/MergeFunc/comdat.ll | 5 +-
.../test/Transforms/MergeFunc/linkonce_odr.ll | 9 ++
.../MergeFunc/merge-linkonce-odr.ll | 112 ++++++++++++++++++
4 files changed, 126 insertions(+), 4 deletions(-)
create mode 100644 llvm/test/Transforms/MergeFunc/merge-linkonce-odr.ll
diff --git a/llvm/lib/Transforms/IPO/MergeFunctions.cpp b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
index d991ec64445ee99..ea5e102156ff766 100644
--- a/llvm/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
@@ -891,8 +891,8 @@ bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
// Merge two equivalent functions. Upon completion, Function G is deleted.
void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
- if (F->isInterposable() || G->hasWeakODRLinkage()) {
- assert(G->isInterposable() || G->hasWeakODRLinkage());
+ if (F->isInterposable() || G->hasWeakODRLinkage() || G->hasLinkOnceODRLinkage()) {
+ assert(G->isInterposable() || G->hasWeakODRLinkage()|| G->hasLinkOnceODRLinkage());
// Both writeThunkOrAlias() calls below must succeed, either because we can
// create aliases for G and NewF, or because a thunk for F is profitable.
diff --git a/llvm/test/Transforms/MergeFunc/comdat.ll b/llvm/test/Transforms/MergeFunc/comdat.ll
index f6e104625bc414c..3770c772b3f88e2 100644
--- a/llvm/test/Transforms/MergeFunc/comdat.ll
+++ b/llvm/test/Transforms/MergeFunc/comdat.ll
@@ -19,6 +19,7 @@ define linkonce_odr hidden i32 @g(i32 %x, i32 %y) comdat {
ret i32 %sum3
}
-; CHECK-DAG: define linkonce_odr hidden i32 @f(i32 %x, i32 %y) comdat
-; CHECK-DAG: define linkonce_odr hidden i32 @g(i32 %0, i32 %1) comdat
+; CHECK-DAG: define private i32 @0(i32 %x, i32 %y) comdat($f)
+; CHECK-DAG: define linkonce_odr hidden i32 @g(i32 %0, i32 %1) comdat {
+; CHECK-DAG: define linkonce_odr hidden i32 @f(i32 %0, i32 %1) {
diff --git a/llvm/test/Transforms/MergeFunc/linkonce_odr.ll b/llvm/test/Transforms/MergeFunc/linkonce_odr.ll
index 23305c04f7b6f40..f403d914eb0f1cc 100644
--- a/llvm/test/Transforms/MergeFunc/linkonce_odr.ll
+++ b/llvm/test/Transforms/MergeFunc/linkonce_odr.ll
@@ -7,10 +7,19 @@
; The problem with this is that the linker could then choose these two stubs
; each of the two modules and we end up with two stubs calling each other.
+; Even a total order based on the names may not be enough, e.g. if @funA calls
+; @funB via function pointer in the other module. Then we could end up in
+; situations where @funB -> @funA in one module (after merging functions) and
+; @funA -> @funB via the a function pointer in the other module.
+
; CHECK-LABEL: define linkonce_odr i32 @funA
; CHECK-NEXT: add
; CHECK: ret
+; CHECK-LABEL: define linkonce_odr i32 @funC
+; CHECK-NEXT: tail call i32 @funA(i32 %0, i32 %1)
+; CHECK-NEXT: ret
+
; CHECK-LABEL: define linkonce_odr i32 @funB
; CHECK-NEXT: tail call i32 @funA(i32 %0, i32 %1)
; CHECK-NEXT: ret
diff --git a/llvm/test/Transforms/MergeFunc/merge-linkonce-odr.ll b/llvm/test/Transforms/MergeFunc/merge-linkonce-odr.ll
new file mode 100644
index 000000000000000..96711265b7f4180
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/merge-linkonce-odr.ll
@@ -0,0 +1,112 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs --version 5
+; RUN: opt -p mergefunc -S %s | FileCheck %s
+
+define linkonce_odr hidden void @linkonce_odr_caller_of_foo_1(ptr %p) {
+entry:
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ ret void
+}
+
+define linkonce_odr hidden void @linkonce_odr_caller_of_foo_2(ptr %p) {
+entry:
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ tail call void @foo(ptr %p)
+ ret void
+}
+
+declare void @foo(ptr)
+
+define hidden void @linkonce_odr_caller_of_bar_1(ptr %p) {
+entry:
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ ret void
+}
+
+define linkonce_odr hidden void @non_linkonce_caller_of_bar_2(ptr %p) {
+entry:
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ tail call void @bar(ptr %p)
+ ret void
+}
+
+declare void @bar(ptr)
+
+define hidden void @non_linkonce_caller_of_zar_1(ptr %p) {
+entry:
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ ret void
+}
+
+define linkonce_odr hidden void @linkonce_odr_caller_of_zar_2(ptr %p) {
+entry:
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ tail call void @zar(ptr %p)
+ ret void
+}
+
+declare void @zar(ptr)
+; CHECK-LABEL: define private void @0(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: tail call void @foo(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define private void @1(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: tail call void @bar(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr hidden void @linkonce_odr_caller_of_zar_2(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: tail call void @zar(ptr [[P]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr hidden void @linkonce_odr_caller_of_foo_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB0:[0-9]+]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr hidden void @linkonce_odr_caller_of_foo_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr hidden void @non_linkonce_caller_of_bar_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB1:[0-9]+]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define hidden void @linkonce_odr_caller_of_bar_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @[[GLOB1]](ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define hidden void @non_linkonce_caller_of_zar_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT: tail call void @linkonce_odr_caller_of_zar_2(ptr [[TMP0]])
+; CHECK-NEXT: ret void
+;
More information about the llvm-commits
mailing list