[llvm] [SampleFDO] Stale profile renaming matching (PR #92151)

[Lei Wang via llvm-commits]

================
@@ -590,13 +609,260 @@ void SampleProfileMatcher::computeAndReportProfileStaleness() {
   }
 }
 
-void SampleProfileMatcher::runOnModule() {
+// Find functions that don't show in the profile or profile symbol list, which
+// are supposed to be new functions. We use them as the targets for renaming
+// matching.
+void SampleProfileMatcher::findIRNewFunctions(
+    StringMap<Function *> &IRNewFunctions) {
+  // TODO: Support MD5 profile.
+  if (FunctionSamples::UseMD5)
+    return;
+  StringSet<> NamesInProfile;
+  if (auto NameTable = Reader.getNameTable()) {
+    for (auto Name : *NameTable)
+      NamesInProfile.insert(Name.stringRef());
+  }
+
+  for (auto &F : M) {
+    // Skip declarations, as even if the function can be recognized renamed, we
+    // have nothing to do with it.
+    if (F.isDeclaration())
+      continue;
+
+    StringRef CanonFName = FunctionSamples::getCanonicalFnName(F.getName());
+    const auto *FS = getFlattenedSamplesFor(F);
+    if (FS)
+      continue;
+
+    // For extended binary, the full function name symbols exits in the profile
+    // symbol list table.
+    if (NamesInProfile.count(CanonFName))
+      continue;
+
+    if (PSL && PSL->contains(CanonFName))
+      continue;
+
+    LLVM_DEBUG(dbgs() << "Function " << CanonFName
+                      << " is not in profile or symbol list table.\n");
+    IRNewFunctions[CanonFName] = &F;
+  }
+}
+
+void SampleProfileMatcher::findIRNewCallees(
+    Function &Caller, const StringMap<Function *> &IRNewFunctions,
+    std::vector<Function *> &IRNewCallees) {
+  for (auto &BB : Caller) {
+    for (auto &I : BB) {
+      const auto *CB = dyn_cast<CallBase>(&I);
+      if (!CB || isa<IntrinsicInst>(&I))
+        continue;
+      Function *Callee = CB->getCalledFunction();
+      if (!Callee || Callee->isDeclaration())
+        continue;
+      StringRef CalleeName =
+          FunctionSamples::getCanonicalFnName(Callee->getName());
+      if (IRNewFunctions.count(CalleeName))
+        IRNewCallees.push_back(Callee);
+    }
+  }
+}
+
+// Use function similarity to determine if the function is renamed. Compute a
+// similarity ratio between two sequences which are  the function callsite
+// anchors. The returned value is in the range [0, 1]. The bigger the value is,
+// the more similar two sequences are.
+float SampleProfileMatcher::checkFunctionSimilarity(
+    const Function &IRFunc, const FunctionId &ProfFName) {
+  AnchorMap IRAnchors;
+  findIRAnchors(IRFunc, IRAnchors);
+
+  AnchorMap ProfileAnchors;
+  const auto *FSFlattened = getFlattenedSamplesFor(ProfFName);
+  assert(FSFlattened && "Flattened profile sample is null");
+  findProfileAnchors(*FSFlattened, ProfileAnchors);
+
+  AnchorList FilteredProfileAnchorList;
+  AnchorList FilteredIRAnchorsList;
+  getFilteredAnchorList(IRAnchors, ProfileAnchors, FilteredIRAnchorsList,
+                        FilteredProfileAnchorList);
+
+  // If the function is probe based, we trust the checksum info to check the
+  // similarity. Otherwise, if the checksum is mismatched, continue computing
+  // the similarity.
+  if (FunctionSamples::ProfileIsProbeBased) {
+    const auto *FuncDesc = ProbeManager->getDesc(IRFunc);
+    // Make sure function is complex enough.
+    if (IRAnchors.size() - FilteredIRAnchorsList.size() > 5 && FuncDesc &&
+        !ProbeManager->profileIsHashMismatched(*FuncDesc, *FSFlattened)) {
----------------
wlei-llvm wrote:

It's the same reason as the above comment, here it needs the num of block(IRAnchors.size() - FilteredIRAnchorsList.size()) which needs to be after the `findIR/Profile anchor` to check if the function is complex enough.

https://github.com/llvm/llvm-project/pull/92151