Add -fdiagnostics-show-hotness

Summary:
I've recently added the ability for optimization remarks to include the
hotness of the corresponding code region.  This uses PGO and allows
filtering of the optimization remarks by relevance.  The idea was first
discussed here:
http://thread.gmane.org/gmane.comp.compilers.llvm.devel/98334

The general goal is to produce a YAML file with the remarks.  Then, an
external tool could dynamically filter these by hotness and perhaps by
other things.

That said it makes sense to also expose this at the more basic level
where we just include the hotness info with each optimization remark.
For example, in D22694, the clang flag was pretty useful to measure the
overhead of the additional analyses required to include hotness.
(Without the flag we don't even run the analyses.)

For the record, Hal has already expressed support for the idea of this
patch on IRC.

Differential Revision: https://reviews.llvm.org/D23284

llvm-svn: 281276

1 files changed, 9 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index dd803909f03..6a3b9c6efbd 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -179,6 +179,7 @@ namespace clang {
           Ctx.getDiagnosticHandler();
       void *OldDiagnosticContext = Ctx.getDiagnosticContext();
       Ctx.setDiagnosticHandler(DiagnosticHandler, this);
+      Ctx.setDiagnosticHotnessRequested(CodeGenOpts.DiagnosticsWithHotness);
 
       // Link LinkModule into this module if present, preserving its validity.
       for (auto &I : LinkModules) {
@@ -511,9 +512,16 @@ void BackendConsumer::EmitOptimizationMessage(
   FullSourceLoc Loc = getBestLocationFromDebugLoc(D, BadDebugInfo, Filename,
       Line, Column);
 
+  std::string Msg;
+  raw_string_ostream MsgStream(Msg);
+  MsgStream << D.getMsg().str();
+
+  if (D.getHotness())
+    MsgStream << " (hotness: " << *D.getHotness() << ")";
+
   Diags.Report(Loc, DiagID)
       << AddFlagValue(D.getPassName() ? D.getPassName() : "")
-      << D.getMsg().str();
+      << MsgStream.str();
 
   if (BadDebugInfo)
     // If we were not able to translate the file:line:col information