[Profile] Add off-by-default -Wprofile-instr-missing warning

Clang warns that a profile is out-of-date if it can't find a profile
record for any function in a TU. This warning became noisy after llvm
started allowing dead-stripping of instrumented functions.

To fix this, this patch changes the existing profile out-of-date warning
(-Wprofile-instr-out-of-date) so that it only complains about mismatched
data. Further, it introduces a new, off-by-default warning about missing
function data (-Wprofile-instr-missing).

Differential Revision: https://reviews.llvm.org/D28867

llvm-svn: 301570

clang/include/clang/Basic/DiagnosticGroups.td

@@ -890,6 +890,7 @@ def BackendOptimizationRemarkAnalysis : DiagGroup<"pass-analysis">;
 def BackendOptimizationFailure : DiagGroup<"pass-failed">;
 
 // Instrumentation based profiling warnings.
+def ProfileInstrMissing : DiagGroup<"profile-instr-missing">;
 def ProfileInstrOutOfDate : DiagGroup<"profile-instr-out-of-date">;
 def ProfileInstrUnprofiled : DiagGroup<"profile-instr-unprofiled">;
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -8938,8 +8938,13 @@ def warn_not_a_doxygen_trailing_member_comment : Warning<
 let CategoryName = "Instrumentation Issue" in {
 def warn_profile_data_out_of_date : Warning<
   "profile data may be out of date: of %0 function%s0, %1 %plural{1:has|:have}1"
-  " no data and %2 %plural{1:has|:have}2 mismatched data that will be ignored">,
+  " mismatched data that will be ignored">,
   InGroup<ProfileInstrOutOfDate>;
+def warn_profile_data_missing : Warning<
+  "profile data may be incomplete: of %0 function%s0, %1 %plural{1:has|:have}1"
+  " no data">,
+  InGroup<ProfileInstrMissing>,
+  DefaultIgnore;
 def warn_profile_data_unprofiled : Warning<
   "no profile data available for file \"%0\"">,
   InGroup<ProfileInstrUnprofiled>;

clang/lib/CodeGen/CodeGenModule.cpp

@@ -369,9 +369,13 @@ void InstrProfStats::reportDiagnostics(DiagnosticsEngine &Diags,
     if (MainFile.empty())
       MainFile = "<stdin>";
     Diags.Report(diag::warn_profile_data_unprofiled) << MainFile;
-  } else
-    Diags.Report(diag::warn_profile_data_out_of_date) << Visited << Missing
-                                                      << Mismatched;
+  } else {
+    if (Mismatched > 0)
+      Diags.Report(diag::warn_profile_data_out_of_date) << Visited << Mismatched;
+
+    if (Missing > 0)
+      Diags.Report(diag::warn_profile_data_missing) << Visited << Missing;
+  }
 }
 
 void CodeGenModule::Release() {

clang/test/Profile/c-outdated-data.c

@@ -4,23 +4,23 @@
 // doesn't play well with warnings that have no line number.
 
 // RUN: llvm-profdata merge %S/Inputs/c-outdated-data.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%t.profdata -Wprofile-instr-dropped 2>&1 | FileCheck %s
-// CHECK: warning: profile data may be out of date: of 3 functions, 1 has no data and 1 has mismatched data that will be ignored
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=NO_MISSING
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -Wprofile-instr-missing -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=WITH_MISSING
+
+// NO_MISSING: warning: profile data may be out of date: of 3 functions, 1 has mismatched data that will be ignored
+// NO_MISSING-NOT: 1 has no data
+
+// WITH_MISSING: warning: profile data may be out of date: of 3 functions, 1 has mismatched data that will be ignored
+// WITH_MISSING: warning: profile data may be incomplete: of 3 functions, 1 has no data
 
 void no_usable_data() {
   int i = 0;
 
   if (i) {}
-
-#ifdef GENERATE_OUTDATED_DATA
-  if (i) {}
-#endif
 }
 
-#ifndef GENERATE_OUTDATED_DATA
 void no_data() {
 }
-#endif
 
 int main(int argc, const char *argv[]) {
   no_usable_data();