[PGO] Stop using invalid char in instr variable names.

Before the patch, -fprofile-instr-generate compile will fail
if no integrated-as is specified when the file contains
any static functions (the -S output is also invalid).

This patch fixed the issue. With the change, the index format
version will be bumped up by 1. Backward compatibility is 
preserved with this change.

Differential Revision: http://reviews.llvm.org/D15243

llvm-svn: 255365
diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
index a965a12..2608847 100644
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -74,14 +74,15 @@
 
 std::string getPGOFuncName(StringRef RawFuncName,
                            GlobalValue::LinkageTypes Linkage,
-                           StringRef FileName,
-                           uint64_t Version LLVM_ATTRIBUTE_UNUSED) {
+                           StringRef FileName, uint64_t Version) {
 
   // Function names may be prefixed with a binary '1' to indicate
   // that the backend should not modify the symbols due to any platform
   // naming convention. Do not include that '1' in the PGO profile name.
   if (RawFuncName[0] == '\1')
     RawFuncName = RawFuncName.substr(1);
+  const char *Unknown = (Version <= 3 ? "<unknown>:" : "__unknown__");
+  const char *Sep = (Version <= 3 ? ":" : "__");
 
   std::string FuncName = RawFuncName;
   if (llvm::GlobalValue::isLocalLinkage(Linkage)) {
@@ -90,9 +91,9 @@
     // that it will stay the same, e.g., if the files are checked out from
     // version control in different locations.
     if (FileName.empty())
-      FuncName = FuncName.insert(0, "<unknown>:");
+      FuncName = FuncName.insert(0, Unknown);
     else
-      FuncName = FuncName.insert(0, FileName.str() + ":");
+      FuncName = FuncName.insert(0, FileName.str() + Sep);
   }
   return FuncName;
 }