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

[via cfe-commits]

================
@@ -433,6 +433,44 @@ using CandidateQueue =
     PriorityQueue<InlineCandidate, std::vector<InlineCandidate>,
                   CandidateComparer>;
 
+// Profile matching statstics.
+class ProfileMatchStats {
+  const Module &M;
+  SampleProfileReader &Reader;
+  const PseudoProbeManager *ProbeManager;
+
+public:
+  ProfileMatchStats(const Module &M, SampleProfileReader &Reader,
+                    const PseudoProbeManager *ProbeManager)
+      : M(M), Reader(Reader), ProbeManager(ProbeManager) {}
+
+  uint64_t NumMismatchedCallsites = 0;
+  uint64_t TotalProfiledCallsites = 0;
+  uint64_t MismatchedCallsiteSamples = 0;
+  uint64_t NumMismatchedFuncHash = 0;
+  uint64_t TotalProfiledFunc = 0;
+  uint64_t MismatchedFuncHashSamples = 0;
+  uint64_t TotalFunctionSamples = 0;
+
+  // A map from function name to a set of mismatched callsite locations.
+  StringMap<std::set<LineLocation>> FuncMismatchedCallsites;
+
+  void countMismatchedSamples(const FunctionSamples &FS);
+  void countProfileMismatches(
+      const Function &F, const std::map<LineLocation, StringRef> &IRAnchors,
+      const std::map<LineLocation, std::unordered_set<FunctionId>>
+          &ProfileAnchors);
+  void countMismatchedCallsites(
+      const Function &F, const std::map<LineLocation, StringRef> &IRAnchors,
+      const std::map<LineLocation, std::unordered_set<FunctionId>>
+          &ProfileAnchors,
+      const LocToLocMap &IRToProfileLocationMap);
+  void countMismatchedCallsiteSamples(const FunctionSamples &FS);
+  void countMismatchedCallsiteSamples();
+  void copyUnchangedCallsiteMismatches(
+      const StringMap<std::set<LineLocation>> &InputMismatchedCallsites);
+};
----------------
WenleiHe wrote:

These functions needs some comments as they are somewhat similar but with subtle differences. 

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