Improve merging of function declarations. Specifically:

  - When we are declaring a function in local scope, we can merge with
    a visible declaration from an outer scope if that declaration
    refers to an entity with linkage. This behavior now works in C++
    and properly ignores entities without linkage.
  - Diagnose the use of "static" on a function declaration in local
    scope.
  - Diagnose the declaration of a static function after a non-static
    declaration of the same function.
  - Propagate the storage specifier to a function declaration from a
    prior declaration (PR3425)
  - Don't name-mangle "main"



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@65360 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/Mangle.cpp b/lib/CodeGen/Mangle.cpp
index f310e98..c802966 100644
--- a/lib/CodeGen/Mangle.cpp
+++ b/lib/CodeGen/Mangle.cpp
@@ -70,7 +70,7 @@
     else if (Context.getSourceManager().getFileCharacteristic(FD->getLocation())
           == SrcMgr::C_ExternCSystem)
       RequiresMangling = false;
-    else if (Context.getLangOptions().CPlusPlus) {
+    else if (Context.getLangOptions().CPlusPlus && !FD->isMain()) {
       // C++ requires name mangling, unless we're in a C linkage
       // specification.
       RequiresMangling = true;