[llvm-profdata] Improve error messaging when merging mismatched profile data

Summary:
This change tries to make the root cause of instrumented profile data merge failures clearer.

Previous:

$ llvm-profdata merge test_0.profraw test_1.profraw -o test_merged.profdata
test_1.profraw: foo: Function count mismatch
test_1.profraw: bar: Function count mismatch
test_1.profraw: baz: Function count mismatch
...

Changed:

$ llvm-profdata merge test_0.profraw test_1.profraw -o test_merged.profdata
test_1.profraw: foo: Function basic block count change detected (counter mismatch)
Make sure that all profile data to be merged is generated from the same binary.
test_1.profraw: bar: Function basic block count change detected (counter mismatch)
test_1.profraw: baz: Function basic block count change detected (counter mismatch)
...

Reviewers: dnovillo, davidxl, bogner

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14739

llvm-svn: 253384

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/ProfileData/InstrProf.cpp b/llvm/lib/ProfileData/InstrProf.cpp
index ef7b19b2882..2dd0f916c6d 100644
--- a/llvm/lib/ProfileData/InstrProf.cpp
+++ b/llvm/lib/ProfileData/InstrProf.cpp
@@ -51,13 +51,13 @@ class InstrProfErrorCategoryType : public std::error_category {
     case instrprof_error::unknown_function:
       return "No profile data available for function";
     case instrprof_error::hash_mismatch:
-      return "Function hash mismatch";
+      return "Function control flow change detected (hash mismatch)";
     case instrprof_error::count_mismatch:
-      return "Function count mismatch";
+      return "Function basic block count change detected (counter mismatch)";
     case instrprof_error::counter_overflow:
       return "Counter overflow";
     case instrprof_error::value_site_count_mismatch:
-      return "Function's value site counts mismatch";
+      return "Function value site count change detected (counter mismatch)";
     }
     llvm_unreachable("A value of instrprof_error has no message.");
   }