Include translation unit filename in global ctor symbol names.

This makes it easier to see where a global ctor comes from, and it also makes
ASan's init order analyzer output easier to understand.  gcc does this too,
but only in -fPIC mode for some reason.  Don't do this for constructors with
explicit init priority.

Also prepend "sub_" before the 'I', that way regular constructors stay
lexicographically after symbols with init priority (because
ord('s') > ord('I')).  gold seems to ignore the name of constructor symbols,
and ld only looks at the symbol if it includes an init priority, which this
patch doesn't change.

Before: __GLOBAL_I_a
Now: __GLOBAL_sub_I_myfile.cc
llvm-svn: 208128
diff --git a/clang/test/CodeGenCXX/globalinit-loc.cpp b/clang/test/CodeGenCXX/globalinit-loc.cpp
index c6c27e3..eb39aec 100644
--- a/clang/test/CodeGenCXX/globalinit-loc.cpp
+++ b/clang/test/CodeGenCXX/globalinit-loc.cpp
@@ -4,9 +4,9 @@
 // Verify that the global init helper function does not get associated
 // with any source location.
 //
-// CHECK: define internal void @_GLOBAL__I_a
+// CHECK: define internal void @_GLOBAL__sub_I_globalinit_loc.cpp
 // CHECK: !dbg ![[DBG:.*]]
-// CHECK: "_GLOBAL__I_a", i32 0, {{.*}}, i32 0} ; [ DW_TAG_subprogram ] [line 0] [local] [def]
+// CHECK: "_GLOBAL__sub_I_globalinit_loc.cpp", i32 0, {{.*}}, i32 0} ; [ DW_TAG_subprogram ] [line 0] [local] [def]
 // CHECK: ![[DBG]] = metadata !{i32 0, i32 0,
 # 99 "someheader.h"
 class A {