[llvm] c796900 - [GlobalOpt] Don't replace aliasee with alias that has weak linkage (#91483)

[via llvm-commits]

Author: DianQK
Date: 2024-05-17T05:51:49+08:00
New Revision: c79690040acf5bb3d857558b0878db47f7f23dc3

URL: https://github.com/llvm/llvm-project/commit/c79690040acf5bb3d857558b0878db47f7f23dc3
DIFF: https://github.com/llvm/llvm-project/commit/c79690040acf5bb3d857558b0878db47f7f23dc3.diff

LOG: [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.

Added: 
    llvm/test/Transforms/GlobalOpt/alias-weak.ll

Modified: 
    llvm/lib/Transforms/IPO/GlobalOpt.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index c8c835115a992..b7c6d25657bc0 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2224,6 +2224,9 @@ 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
+;