[PGO] Shorten profile symbol prefixes

(test case update)
Profile symbols have long prefixes which waste space and creating pressure for linker.
This patch shortens the prefixes to minimal length without losing verbosity.

Differential Revision: http://reviews.llvm.org/D15503

llvm-svn: 255576
diff --git a/clang/test/Profile/cxx-rangefor.cpp b/clang/test/Profile/cxx-rangefor.cpp
index 23be0f5..d5ac4f8 100644
--- a/clang/test/Profile/cxx-rangefor.cpp
+++ b/clang/test/Profile/cxx-rangefor.cpp
@@ -7,7 +7,7 @@
 // RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-rangefor.cpp -std=c++11 -o - -emit-llvm -fprofile-instr-use=%t.profdata > %tuse
 // RUN: FileCheck --input-file=%tuse -check-prefix=CHECK -check-prefix=PGOUSE %s
 
-// PGOGEN: @[[RFC:__llvm_profile_counters__Z9range_forv]] = private global [5 x i64] zeroinitializer
+// PGOGEN: @[[RFC:__prf_cn__Z9range_forv]] = private global [5 x i64] zeroinitializer
 
 // CHECK-LABEL: define {{.*}}void @_Z9range_forv()
 // PGOGEN: store {{.*}} @[[RFC]], i64 0, i64 0