[llvm-branch-commits] [llvm] release/18.x: [GlobalOpt] Don't replace aliasee with alias that has weak linkage (#91483) (PR #92468)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/92468

Backport c79690040acf5bb3d857558b0878db47f7f23dc3

Requested by: @DianQK

>From 012e13b1594ba19058294d793993ad8da14c9159 Mon Sep 17 00:00:00 2001
From: DianQK <dianqk at dianqk.net>
Date: Fri, 17 May 2024 05:51:49 +0800
Subject: [PATCH] [GlobalOpt] Don't replace aliasee with alias that has weak
 linkage (#91483)

Fixes #91312.

Don't perform the transform if the alias may be replaced at link time.

(cherry picked from commit c79690040acf5bb3d857558b0878db47f7f23dc3)
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp        |  3 ++
 llvm/test/Transforms/GlobalOpt/alias-weak.ll | 57 ++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 llvm/test/Transforms/GlobalOpt/alias-weak.ll

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 951372adcfa93..619b3f612f25f 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2212,6 +2212,9 @@ static bool mayHaveOtherReferences(GlobalValue &GV, const LLVMUsed &U) {
 
 static bool hasUsesToReplace(GlobalAlias &GA, const LLVMUsed &U,
                              bool &RenameTarget) {
+  if (GA.isWeakForLinker())
+    return false;
+
   RenameTarget = false;
   bool Ret = false;
   if (hasUseOtherThanLLVMUsed(GA, U))
diff --git a/llvm/test/Transforms/GlobalOpt/alias-weak.ll b/llvm/test/Transforms/GlobalOpt/alias-weak.ll
new file mode 100644
index 0000000000000..aec2a56313b12
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/alias-weak.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --include-generated-funcs --version 4
+; RUN: opt < %s -passes=globalopt -S | FileCheck %s
+
+ at f1_alias = linkonce_odr hidden alias void (), ptr @f1
+ at f2_alias = linkonce_odr hidden alias void (), ptr @f2
+
+define void @foo() {
+  call void @f1_alias()
+  ret void
+}
+
+define void @bar() {
+  call void @f1()
+  ret void
+}
+
+define void @baz() {
+  call void @f2_alias()
+  ret void
+}
+
+; We cannot use `f1_alias` to replace `f1` because they are both in use
+; and `f1_alias` could be replaced at link time.
+define internal void @f1() {
+  ret void
+}
+
+; FIXME: We can use `f2_alias` to replace `f2` because `b2` is not in use.
+define internal void @f2() {
+  ret void
+}
+;.
+; CHECK: @f1_alias = linkonce_odr hidden alias void (), ptr @f1
+; CHECK: @f2_alias = linkonce_odr hidden alias void (), ptr @f2
+;.
+; CHECK-LABEL: define void @foo() local_unnamed_addr {
+; CHECK-NEXT:    call void @f1_alias()
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define void @bar() local_unnamed_addr {
+; CHECK-NEXT:    call void @f1()
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define void @baz() local_unnamed_addr {
+; CHECK-NEXT:    call void @f2_alias()
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define internal void @f1() {
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define internal void @f2() {
+; CHECK-NEXT:    ret void
+;