[PGO] Fix bogus warning for merging empty llvm profile file

Profile runtime can generate an empty raw profile (when there is no function in
the shared library). This empty profile is treated as a text format profile.  A
test format profile without the flag of "#IR" is thought to be a clang
generated profile.  So in llvm profile merging, we will get a bogus warning of
"Merge IR generated profile with Clang generated profile."

The fix here is to skip the empty profile (when the buffer size is 0) for
profile merge.

Reviewers: vsk, davidxl

Differential Revision: http://reviews.llvm.org/D25687

llvm-svn: 284659

llvm/include/llvm/ProfileData/InstrProf.h

@@ -292,7 +292,8 @@ enum class instrprof_error {
   counter_overflow,
   value_site_count_mismatch,
   compress_failed,
-  uncompress_failed
+  uncompress_failed,
+  empty_raw_profile
 };
 
 inline std::error_code make_error_code(instrprof_error E) {

llvm/lib/ProfileData/InstrProf.cpp

@@ -70,6 +70,8 @@ std::string getInstrProfErrString(instrprof_error Err) {
     return "Failed to compress data (zlib)";
   case instrprof_error::uncompress_failed:
     return "Failed to uncompress data (zlib)";
+  case instrprof_error::empty_raw_profile:
+    return "Empty raw profile file";
   }
   llvm_unreachable("A value of instrprof_error has no message.");
 }

llvm/lib/ProfileData/InstrProfReader.cpp

@@ -46,6 +46,9 @@ InstrProfReader::create(std::unique_ptr<MemoryBuffer> Buffer) {
   if (Buffer->getBufferSize() > std::numeric_limits<unsigned>::max())
     return make_error<InstrProfError>(instrprof_error::too_large);
 
+  if (Buffer->getBufferSize() == 0)
+    return make_error<InstrProfError>(instrprof_error::empty_raw_profile);
+
   std::unique_ptr<InstrProfReader> Result;
   // Create the reader.
   if (IndexedInstrProfReader::hasFormat(*Buffer))

llvm/test/tools/llvm-profdata/Inputs/IR_profile.proftext

@@ -0,0 +1,9 @@
+:ir
+main
+# Func Hash:
+12884901887
+# Num Counters:
+1
+# Counter Values:
+1
+

llvm/test/tools/llvm-profdata/Inputs/clang_profile.proftext

@@ -0,0 +1,8 @@
+main
+# Func Hash:
+0
+# Num Counters:
+1
+# Counter Values:
+1
+

llvm/test/tools/llvm-profdata/merge_empty_profile.test

@@ -0,0 +1,17 @@
+# Tests for merge of empty profile files.
+
+RUN: touch %t_empty.proftext
+RUN: llvm-profdata merge -text -o %t_clang.proftext %t_empty.proftext %p/Inputs/clang_profile.proftext
+RUN: FileCheck --input-file=%t_clang.proftext %s -check-prefix=CLANG_PROF_TEXT
+CLANG_PROF_TEXT: main
+CLANG_PROF_TEXT: 0
+CLANG_PROF_TEXT: 1
+CLANG_PROF_TEXT: 1
+
+RUN: llvm-profdata merge -text -o %t_ir.proftext %t_empty.proftext %p/Inputs/IR_profile.proftext
+RUN: FileCheck --input-file=%t_ir.proftext %s -check-prefix=IR_PROF_TEXT
+IR_PROF_TEXT: :ir
+IR_PROF_TEXT: main
+IR_PROF_TEXT: 0
+IR_PROF_TEXT: 1
+IR_PROF_TEXT: 1

llvm/tools/llvm-profdata/llvm-profdata.cpp

@@ -140,8 +140,13 @@ static void loadInput(const WeightedFile &Input, WriterContext *WC) {
   WC->ErrWhence = Input.Filename;
 
   auto ReaderOrErr = InstrProfReader::create(Input.Filename);
-  if ((WC->Err = ReaderOrErr.takeError()))
+  if (Error E = ReaderOrErr.takeError()) {
+    // Skip the empty profiles by returning sliently.
+    instrprof_error IPE = InstrProfError::take(std::move(E));
+    if (IPE != instrprof_error::empty_raw_profile)
+      WC->Err = make_error<InstrProfError>(IPE);
     return;
+  }
 
   auto Reader = std::move(ReaderOrErr.get());
   bool IsIRProfile = Reader->isIRLevelProfile();