[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 c796900)

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))

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
+
+@f1_alias = linkonce_odr hidden alias void (), ptr @f1
+@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
+;