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

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.

Fixes [clang codegen][regression] VTT definitions missing
dso_local/hidden/etc markings #72451

Author: bd1976bris

clang/lib/CodeGen/CGVTT.cpp

@@ -93,6 +93,11 @@ CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
 
   if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
     VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
+
+  // 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);
 }
 
 llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {

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.
 }