[clang] [clang codegen][regression] Add dso_local/hidden/etc. markings to VTT definitions and declarations (PR #72452)

[via cfe-commits]

https://github.com/bd1976bris updated https://github.com/llvm/llvm-project/pull/72452

>From f6e400224b3a90b4ec47bce2212a8e760b0fe9d8 Mon Sep 17 00:00:00 2001
From: Ben Dunbobbin <Ben.Dunbobbin at sony.com>
Date: Wed, 15 Nov 2023 23:09:41 +0000
Subject: [PATCH 1/2] [clang codegen] Add dso_local/hidden/etc. markings to VTT
 definitions and declarations

https://reviews.llvm.org/D128482 regressed certain cases of VTT
emission which are no longer hidden with -fvisibility=hidden.

Fix this regression by marking both declarations and definitions.
---
 clang/lib/CodeGen/CGVTT.cpp          | 3 +++
 clang/test/CodeGenCXX/visibility.cpp | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/clang/lib/CodeGen/CGVTT.cpp b/clang/lib/CodeGen/CGVTT.cpp
index 22790147c6f5a9f..0eab677ca68a85a 100644
--- a/clang/lib/CodeGen/CGVTT.cpp
+++ b/clang/lib/CodeGen/CGVTT.cpp
@@ -93,6 +93,9 @@ CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
 
   if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
     VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
+
+  // Set the right visibility.
+  CGM.setGVProperties(VTT, RD);
 }
 
 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
diff --git a/clang/test/CodeGenCXX/visibility.cpp b/clang/test/CodeGenCXX/visibility.cpp
index b017bc8b52d5a5d..e307b8747c84779 100644
--- a/clang/test/CodeGenCXX/visibility.cpp
+++ b/clang/test/CodeGenCXX/visibility.cpp
@@ -206,6 +206,9 @@ namespace test27 {
 // CHECK: @_ZGVZN6test681fC1EvE4test = linkonce_odr global
 // CHECK-HIDDEN: @_ZGVZN6test681fC1EvE4test = linkonce_odr hidden global
 
+// CHECK-HIDDEN: @_ZTVN6test701DE = linkonce_odr hidden unnamed_addr constant { [3 x ptr] } { [3 x ptr] [ptr null, ptr null, ptr @_ZTIN6test701DE] }, align 8
+// CHECK-HIDDEN: @_ZTTN6test701DE = linkonce_odr hidden unnamed_addr constant [1 x ptr] [ptr getelementptr inbounds ({ [3 x ptr] }, ptr @_ZTVN6test701DE, i32 0, inrange i32 0, i32 3)], align 8
+
 // CHECK: @_ZZN6Test193fooIiEEvvE1a = linkonce_odr global
 // CHECK-HIDDEN: @_ZZN6Test193fooIiEEvvE1a = linkonce_odr hidden global
 
@@ -1422,6 +1425,12 @@ namespace test70 {
     ~B();
   };
   B::~B() {}
+
+  // Make sure both the vtable and VTT declarations are marked "hidden"
+  // when "-fvisibilty=hidden" is in use.
+  class C {};
+  class D : virtual C {};
+  D d;
   // Check lines at top of file.
 }
 

>From af47d617be5bdbd2b6cbf438a9a5c2f89fe8f3f8 Mon Sep 17 00:00:00 2001
From: Ben Dunbobbin <Ben.Dunbobbin at sony.com>
Date: Tue, 21 Nov 2023 00:55:26 +0000
Subject: [PATCH 2/2] Add comment to explain why the visibility is recomputed
 for VTT definitions

---
 clang/lib/CodeGen/CGVTT.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/clang/lib/CodeGen/CGVTT.cpp b/clang/lib/CodeGen/CGVTT.cpp
index 0eab677ca68a85a..1d3f14f1c5344d7 100644
--- a/clang/lib/CodeGen/CGVTT.cpp
+++ b/clang/lib/CodeGen/CGVTT.cpp
@@ -94,7 +94,9 @@ CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
   if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
     VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
 
-  // Set the right visibility.
+  // Set the visibility. This will already have been set on the VTT declaration.
+  // Set it again, now that we have a definition, as the implicit visibility can
+  // apply differently to definitions.
   CGM.setGVProperties(VTT, RD);
 }