[CodeGen] Treat auto-generated __dso_handle symbol as HiddenVisibility

[mcgrathr]

Summary

Fixes https://llvm.org/bugs/show_bug.cgi?id=31932

[mcgrathr]

This is for clang, not llvm. Should it be cfe-commits instead of llvm-commits?

[phosek]

In D29843#674111, @mcgrathr wrote:

This is for clang, not llvm. Should it be cfe-commits instead of llvm-commits?

Right, my mistake.

[phosek]

Did you run all tests? I'd suspect that this might break test/OpenMP/threadprivate_codegen.cpp which is expecting @__dso_handle = external global i8 which will now be hidden global?

[mcgrathr]

This was just the first crack, my first attempt at any change in LLVMland. I don't know how to run the tests yet.

[phosek]

You can use ninja check-clang to run Clang tests, if those pass you can use ninja check-all to run all tests. Testing guide has details about testing in LLVM.

[mcgrathr]

This now passes check-clang.

[phosek]

LGTM

[joerg]

lib/CodeGen/CodeGenModule.cpp

2402

Can't this use the VarDecl argument of GetOrCreateLLVMGlobal to set the visibility? I'd prefer to keep reundant arguments to a minimum.

[rnk]

I committed a modified patch that set the visibility on the global after creating it to avoid adding an optional boolean parameter. Thanks for the report and patch!

lib/CodeGen/CodeGenModule.h

                                           llvm::AttributeSet());
   /// Create a new runtime global variable with the specified type and name.
   llvm::Constant *CreateRuntimeVariable(llvm::Type *Ty,
-                                        StringRef Name);
+                                        StringRef Name,
+                                        bool Hidden = false);
 
   ///@name Custom Blocks Runtime Interfaces
   ///@{

                                         llvm::PointerType *PTy,
                                         const VarDecl *D,
                                         ForDefinition_t IsForDefinition
-                                          = NotForDefinition);
+                                          = NotForDefinition,
+                                        bool Hidden = false);
 
   void setNonAliasAttributes(const Decl *D, llvm::GlobalObject *GO);
 

lib/CodeGen/CodeGenModule.cpp

 CodeGenModule::GetOrCreateLLVMGlobal(StringRef MangledName,
                                      llvm::PointerType *Ty,
                                      const VarDecl *D,
-                                     ForDefinition_t IsForDefinition) {
+                                     ForDefinition_t IsForDefinition,
+                                     bool Hidden) {
   // Lookup the entry, lazily creating it if necessary.
   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
   if (Entry) {

         D->getType().isConstant(Context) &&
         isExternallyVisible(D->getLinkageAndVisibility().getLinkage()))
       GV->setSection(".cp.rodata");
+  } else if (Hidden) {
+    GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
   }
 
   if (AddrSpace != Ty->getAddressSpace())

 /// specified type and name.
 llvm::Constant *
 CodeGenModule::CreateRuntimeVariable(llvm::Type *Ty,
-                                     StringRef Name) {
-  return GetOrCreateLLVMGlobal(Name, llvm::PointerType::getUnqual(Ty), nullptr);
+                                     StringRef Name,
+                                     bool Hidden) {
+  return GetOrCreateLLVMGlobal(Name, llvm::PointerType::getUnqual(Ty), nullptr,
+                               NotForDefinition, Hidden);
 }
 
 void CodeGenModule::EmitTentativeDefinition(const VarDecl *D) {

lib/CodeGen/ItaniumCXXABI.cpp

 
   // Create a variable that binds the atexit to this shared object.
   llvm::Constant *handle =
-    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
+    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle", true);
 
   llvm::Value *args[] = {
     llvm::ConstantExpr::getBitCast(dtor, dtorTy),