[llvm] [libcxxabi] [clang] [lld] [compiler-rt] [libcxx] [flang] [libc] [clang-tools-extra] [CSSPGO] Compute and report post-match profile staleness (PR #79090)

[via cfe-commits]

================
@@ -2460,63 +2528,108 @@ void SampleProfileMatcher::runOnFunction(const Function &F) {
       !ProbeManager->profileIsValid(F, *FSFlattened)) {
     // The matching result will be saved to IRToProfileLocationMap, create a new
     // map for each function.
+    auto &IRToProfileLocationMap = getIRToProfileLocationMap(F);
     runStaleProfileMatching(F, IRAnchors, ProfileAnchors,
-                            getIRToProfileLocationMap(F));
+                            IRToProfileLocationMap);
+    PostMatchStats.countMismatchedCallsites(F, IRAnchors, ProfileAnchors,
+                                            IRToProfileLocationMap);
   }
 }
 
-void SampleProfileMatcher::runOnModule() {
-  ProfileConverter::flattenProfile(Reader.getProfiles(), FlattenedProfiles,
-                                   FunctionSamples::ProfileIsCS);
-  for (auto &F : M) {
-    if (F.isDeclaration() || !F.hasFnAttribute("use-sample-profile"))
-      continue;
-    runOnFunction(F);
-  }
-  if (SalvageStaleProfile)
-    distributeIRToProfileLocationMap();
-
+void SampleProfileMatcher::reportOrPersistProfileStats() {
   if (ReportProfileStaleness) {
     if (FunctionSamples::ProfileIsProbeBased) {
-      errs() << "(" << NumMismatchedFuncHash << "/" << TotalProfiledFunc << ")"
+      errs() << "(" << PreMatchStats.NumMismatchedFuncHash << "/"
+             << PreMatchStats.TotalProfiledFunc << ")"
              << " of functions' profile are invalid and "
-             << " (" << MismatchedFuncHashSamples << "/" << TotalFuncHashSamples
-             << ")"
+             << " (" << PreMatchStats.MismatchedFuncHashSamples << "/"
+             << PreMatchStats.TotalFunctionSamples << ")"
              << " of samples are discarded due to function hash mismatch.\n";
     }
-    errs() << "(" << NumMismatchedCallsites << "/" << TotalProfiledCallsites
-           << ")"
+    errs() << "(" << PreMatchStats.NumMismatchedCallsites << "/"
+           << PreMatchStats.TotalProfiledCallsites << ")"
            << " of callsites' profile are invalid and "
-           << "(" << MismatchedCallsiteSamples << "/" << TotalCallsiteSamples
-           << ")"
+           << "(" << PreMatchStats.MismatchedCallsiteSamples << "/"
+           << PreMatchStats.TotalFunctionSamples << ")"
            << " of samples are discarded due to callsite location mismatch.\n";
+    if (SalvageStaleProfile) {
+      uint64_t NumRecoveredCallsites = PostMatchStats.TotalProfiledCallsites -
+                                       PostMatchStats.NumMismatchedCallsites;
+      uint64_t NumMismatchedCallsites =
+          PreMatchStats.NumMismatchedCallsites - NumRecoveredCallsites;
+      errs() << "Out of " << PostMatchStats.TotalProfiledCallsites
+             << " callsites used for profile matching, "
+             << NumRecoveredCallsites
+             << " callsites have been recovered. After the matching, ("
+             << NumMismatchedCallsites << "/"
+             << PreMatchStats.TotalProfiledCallsites
+             << ") of callsites are still invalid ("
+             << PostMatchStats.MismatchedCallsiteSamples << "/"
+             << PreMatchStats.TotalFunctionSamples << ")"
+             << " of samples are still discarded.\n";
+    }
   }
 
   if (PersistProfileStaleness) {
     LLVMContext &Ctx = M.getContext();
     MDBuilder MDB(Ctx);
 
     SmallVector<std::pair<StringRef, uint64_t>> ProfStatsVec;
+    ProfStatsVec.emplace_back("NumMismatchedCallsites",
+                              PreMatchStats.NumMismatchedCallsites);
+    ProfStatsVec.emplace_back("TotalProfiledCallsites",
+                              PreMatchStats.TotalProfiledCallsites);
+    ProfStatsVec.emplace_back("MismatchedCallsiteSamples",
+                              PreMatchStats.MismatchedCallsiteSamples);
+    ProfStatsVec.emplace_back("TotalProfiledFunc",
+                              PreMatchStats.TotalProfiledFunc);
+    ProfStatsVec.emplace_back("TotalFunctionSamples",
+                              PreMatchStats.TotalFunctionSamples);
     if (FunctionSamples::ProfileIsProbeBased) {
-      ProfStatsVec.emplace_back("NumMismatchedFuncHash", NumMismatchedFuncHash);
-      ProfStatsVec.emplace_back("TotalProfiledFunc", TotalProfiledFunc);
+      ProfStatsVec.emplace_back("NumMismatchedFuncHash",
+                                PreMatchStats.NumMismatchedFuncHash);
       ProfStatsVec.emplace_back("MismatchedFuncHashSamples",
-                                MismatchedFuncHashSamples);
-      ProfStatsVec.emplace_back("TotalFuncHashSamples", TotalFuncHashSamples);
+                                PreMatchStats.MismatchedFuncHashSamples);
+    }
+    if (SalvageStaleProfile) {
+      ProfStatsVec.emplace_back("PostMatchNumMismatchedCallsites",
+                                PostMatchStats.NumMismatchedCallsites);
+      ProfStatsVec.emplace_back("NumCallsitesForMatching",
+                                PostMatchStats.TotalProfiledCallsites);
+      ProfStatsVec.emplace_back("PostMatchMismatchedCallsiteSamples",
+                                PostMatchStats.MismatchedCallsiteSamples);
     }
-
-    ProfStatsVec.emplace_back("NumMismatchedCallsites", NumMismatchedCallsites);
-    ProfStatsVec.emplace_back("TotalProfiledCallsites", TotalProfiledCallsites);
-    ProfStatsVec.emplace_back("MismatchedCallsiteSamples",
-                              MismatchedCallsiteSamples);
-    ProfStatsVec.emplace_back("TotalCallsiteSamples", TotalCallsiteSamples);
 
     auto *MD = MDB.createLLVMStats(ProfStatsVec);
     auto *NMD = M.getOrInsertNamedMetadata("llvm.stats");
     NMD->addOperand(MD);
   }
 }
 
+void SampleProfileMatcher::runOnModule() {
+  ProfileConverter::flattenProfile(Reader.getProfiles(), FlattenedProfiles,
+                                   FunctionSamples::ProfileIsCS);
+  for (auto &F : M) {
+    if (ShouldSkipProfileLoading(F))
+      continue;
+    runOnFunction(F);
+  }
+
+  if (SalvageStaleProfile)
+    distributeIRToProfileLocationMap();
+
+  PreMatchStats.countMismatchedCallsiteSamples();
+  if (SalvageStaleProfile) {
+    // If a function doesn't run the matching but has mismatched callsites, this
+    // won't be any data for that function in post-match stats, so just reuse
+    // the pre-match stats.
+    PostMatchStats.copyUnchangedCallsiteMismatches(
+        PreMatchStats.FuncMismatchedCallsites);
+    PostMatchStats.countMismatchedCallsiteSamples();
----------------
WenleiHe wrote:

I see two problems: 
1. We could end up just copying the same mismatched call sites and creating duplicates.
2. The *counting* is somewhat spread out and tangled with matching -- there is `countProfileMismatches` and `countMismatchedCallsites` in function level `runStaleProfileMatching`; then there is counting again here at module level. 

How about we make these changes:
1. Move FuncMismatchedCallsites out of stat class
2. Make FuncMismatchedCallsites `StringMap<std::unordered_map<LineLocation,bool>>` with the boolean indicating whether the input mismatch was recovered by fuzzy matching. 
3. During function level `runStaleProfileMatching`, we only populate and update `FuncMismatchedCallsites`, but not doing any stats. We do stats all at the end on module level.

This is try to create clearer separation between matching and stats, and also be consistent as to at which level stats are done (function or module).

https://github.com/llvm/llvm-project/pull/79090