[PGO] Add flags to control IRPGO warnings.

[JakeVanAdrighem]

Summary

Currently there is no reasonable way to control the warnings in the 'use' phase of the IRPGO pass. This is problematic because the output can be somewhat spammy. This patch adds some flags which allow us to optionally disable these warnings. The current upstream behavior will remain the default.

[davidxl]

lgtm.

Question : do you get warnings when there is no source change? This indicates some potential bugs in compiler. If you see them, can you help file bugs?

[JakeVanAdrighem]

Great, if possible Sean or David could you commit this for me? I don't have
commit access.

As for your question. Sean and I have actually experienced warnings
resulting from a difference in inlining choices in different TU's but we
will definitely be bringing this up very soon as a separate discussion.
These flags were mostly to deal with instrprof_error::unknown_function
which for our use case tends to be pretty spammy but not very helpful.

[xur]

It's good to add options to control the warning -- sometime there are just too many warnings.
But I would suggest to separate this from the stats collection. This patch disables it altogether with the message.

[JakeVanAdrighem]

The meaning/name of the flags have been changed so that we only pass them to disable the warnings. The flags also no longer interfere with the statistics.

[JakeVanAdrighem]

clang-format.

[xur]

Looks good to me.
I will submit this patch for you.

Thanks for improving this.

llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

 
 // Command line option to set the maximum number of VP annotations to write to
 // the metadata for a single indirect call callsite.
 static cl::opt<unsigned> MaxNumAnnotations(
     "icp-max-annotations", cl::init(3), cl::Hidden, cl::ZeroOrMore,
     cl::desc("Max number of annotations for a single indirect "
              "call callsite"));
 
+// Command line option to enable/disable the warning about missing profile
+// information.
+static cl::opt<bool> NoPGOWarnMissing("no-pgo-warn-missing", cl::init(false),
+                                      cl::Hidden);
+
+// Command line option to enable/disable the warning about a hash mismatch in
+// the profile data.
+static cl::opt<bool> NoPGOWarnMismatch("no-pgo-warn-mismatch", cl::init(false),
+                                       cl::Hidden);
+
 namespace {
 class PGOInstrumentationGenLegacyPass : public ModulePass {
 public:
   static char ID;
 
   PGOInstrumentationGenLegacyPass() : ModulePass(ID) {
     initializePGOInstrumentationGenLegacyPassPass(
         *PassRegistry::getPassRegistry());

 // Read the profile from ProfileFileName and assign the value to the
 // instrumented BB and the edges. This function also updates ProgramMaxCount.
 // Return true if the profile are successfully read, and false on errors.
 bool PGOUseFunc::readCounters(IndexedInstrProfReader *PGOReader) {
   auto &Ctx = M->getContext();
   ErrorOr<InstrProfRecord> Result =
       PGOReader->getInstrProfRecord(FuncInfo.FuncName, FuncInfo.FunctionHash);
   if (std::error_code EC = Result.getError()) {
-    if (EC == instrprof_error::unknown_function)
+    if (EC == instrprof_error::unknown_function) {
       NumOfPGOMissing++;
-    else if (EC == instrprof_error::hash_mismatch ||
-             EC == llvm::instrprof_error::malformed)
+      if (NoPGOWarnMissing)
+        return false;
+    } else if (EC == instrprof_error::hash_mismatch ||
+               EC == llvm::instrprof_error::malformed) {
       NumOfPGOMismatch++;
+      if (NoPGOWarnMismatch)
+        return false;
+    }
 
     std::string Msg = EC.message() + std::string(" ") + F.getName().str();
     Ctx.diagnose(
         DiagnosticInfoPGOProfile(M->getName().data(), Msg, DS_Warning));
     return false;
   }
   ProfileRecord = std::move(Result.get());
   std::vector<uint64_t> &CountFromProfile = ProfileRecord.Counts;