Mangle predefined string constants names to merge them at link-time

[samsonov]

Summary

This change generalizes the code used to create global LLVM
variables referencing predefined strings (e.g. FUNCTION): now it
just calls GetAddrOfConstantStringFromLiteral method. As a result,
global variables for these predefined strings may get mangled names
and linkonce_odr linkage. Fix the test accordingly.

[majnemer]

This is compatible with MSVC, LGTM.

lib/CodeGen/CGExpr.cpp

return MakeAddrLValue(CGM.GetAddrOfConstantStringFromLiteral(E),
                         E->getType());
 }
 
 LValue CodeGenFunction::EmitObjCEncodeExprLValue(const ObjCEncodeExpr *E) {
   return MakeAddrLValue(CGM.GetAddrOfConstantStringFromObjCEncode(E),
                         E->getType());
 }
 
-static llvm::Constant*
-GetAddrOfConstantWideString(StringRef Str,
-                            const char *GlobalName,
-                            ASTContext &Context,
-                            QualType Ty, SourceLocation Loc,
-                            CodeGenModule &CGM) {
-
-  StringLiteral *SL = StringLiteral::Create(Context,
-                                            Str,
-                                            StringLiteral::Wide,
-                                            /*Pascal = */false,
-                                            Ty, Loc);
-  llvm::Constant *C = CGM.GetConstantArrayFromStringLiteral(SL);
-  auto *GV = new llvm::GlobalVariable(
-      CGM.getModule(), C->getType(), !CGM.getLangOpts().WritableStrings,
-      llvm::GlobalValue::PrivateLinkage, C, GlobalName);
-  const unsigned WideAlignment =
-    Context.getTypeAlignInChars(Ty).getQuantity();
-  GV->setAlignment(WideAlignment);
-  return GV;
-}
-
 static void ConvertUTF8ToWideString(unsigned CharByteWidth, StringRef Source,
                                     SmallString<32>& Target) {
   Target.resize(CharByteWidth * (Source.size() + 1));
   char *ResultPtr = &Target[0];
   const UTF8 *ErrorPtr;
   bool success = ConvertUTF8toWide(CharByteWidth, Source, ResultPtr, ErrorPtr);
   (void)success;
   assert(success);
if (isa<BlockDecl>(CurDecl)) {
                  FunctionName.size() &&
              "Computed __func__ length differs from type!");
     }
 
     llvm::Constant *C;
     if (ElemType->isWideCharType()) {
       SmallString<32> RawChars;
       ConvertUTF8ToWideString(
-          getContext().getTypeSizeInChars(ElemType).getQuantity(),
-          FunctionName, RawChars);
-      C = GetAddrOfConstantWideString(RawChars,
-                                      GVName.c_str(),
-                                      getContext(),
-                                      E->getType(),
-                                      E->getLocation(),
-                                      CGM);
+          getContext().getTypeSizeInChars(ElemType).getQuantity(), FunctionName,
+          RawChars);
+      StringLiteral *SL = StringLiteral::Create(
+          getContext(), RawChars, StringLiteral::Wide,
+          /*Pascal = */ false, E->getType(), E->getLocation());
+      C = CGM.GetAddrOfConstantStringFromLiteral(SL);
     } else {
       C = CGM.GetAddrOfConstantCString(FunctionName, GVName.c_str(), 1);
     }
     return MakeAddrLValue(C, E->getType());
   }
   }
 }
 

test/CodeGenCXX/ms_wide_predefined_expr.cpp

 // RUN: %clang_cc1 %s -fms-extensions -triple i686-pc-win32 -emit-llvm -o - | FileCheck %s
 
-// CHECK: @"L__FUNCTION__.?func@@YAXXZ" = private constant [5 x i16] [i16 102, i16 117, i16 110, i16 99, i16 0], align 2
+// CHECK: @"\01??_C@_19DPFBEKIN@?$AAf?$AAu?$AAn?$AAc?$AA?$AA@" = linkonce_odr unnamed_addr constant [5 x i16] [i16 102, i16 117, i16 110, i16 99, i16 0], align 2
 
 void wprint(const wchar_t*);
 
 #define __STR2WSTR(str) L##str
 #define _STR2WSTR(str) __STR2WSTR(str)
 #define STR2WSTR(str) _STR2WSTR(str)
 
 void func() {