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, 6 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 619ea9cc231..1536738c926 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -839,6 +839,12 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     NeedLocTracking = true;
   }
 
+  Opts.DiagnosticsWithHotness =
+      Args.hasArg(options::OPT_fdiagnostics_show_hotness);
+  if (Opts.DiagnosticsWithHotness &&
+      Opts.getProfileUse() == CodeGenOptions::ProfileNone)
+    Diags.Report(diag::warn_drv_fdiagnostics_show_hotness_requires_pgo);
+
   // If the user requested to use a sample profile for PGO, then the
   // backend will need to track source location information so the profile
   // can be incorporated into the IR.