[Driver] Add -fdiagnostics-hotness-threshold

Summary:
Depends on https://reviews.llvm.org/D34867.

Add a Clang frontend option to enable optimization remark hotness
thresholds, which were added to LLVM in https://reviews.llvm.org/D34867.
This prevents diagnostics that do not meet a minimum hotness
threshold from being output. When generating optimization remarks for large
codebases with a ton of cold code paths, this option can be used
to limit the optimization remark output at a reasonable size.
Discussion of this change can be read here:
http://lists.llvm.org/pipermail/llvm-dev/2017-June/114377.html

Reviewers: anemet, davidxl, hfinkel

Reviewed By: anemet

Subscribers: fhahn, cfe-commits

Differential Revision: https://reviews.llvm.org/D34868

llvm-svn: 306945

1 files changed, 12 insertions, 6 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index b1b10ddf965..5851595dab7 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -909,12 +909,18 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.DiagnosticsWithHotness =
       Args.hasArg(options::OPT_fdiagnostics_show_hotness);
   bool UsingSampleProfile = !Opts.SampleProfileFile.empty();
-
-  if (Opts.DiagnosticsWithHotness &&
-      Opts.getProfileUse() == CodeGenOptions::ProfileNone &&
-      !UsingSampleProfile) {
-    Diags.Report(diag::warn_drv_fdiagnostics_show_hotness_requires_pgo);
-  }
+  bool UsingProfile = UsingSampleProfile ||
+      (Opts.getProfileUse() != CodeGenOptions::ProfileNone);
+
+  if (Opts.DiagnosticsWithHotness && !UsingProfile)
+    Diags.Report(diag::warn_drv_diagnostics_hotness_requires_pgo)
+        << "-fdiagnostics-show-hotness";
+
+  Opts.DiagnosticsHotnessThreshold = getLastArgUInt64Value(
+      Args, options::OPT_fdiagnostics_hotness_threshold_EQ, 0);
+  if (Opts.DiagnosticsHotnessThreshold > 0 && !UsingProfile)
+    Diags.Report(diag::warn_drv_diagnostics_hotness_requires_pgo)
+        << "-fdiagnostics-hotness-threshold=";
 
   // If the user requested to use a sample profile for PGO, then the
   // backend will need to track source location information so the profile