[llvm] [SampleFDO] Stale profile renaming matching (PR #92151)
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llvm-commits at lists.llvm.org
Fri May 17 21:17:01 PDT 2024
================
@@ -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)) {
+ return 1.0;
+ }
+ }
+
+ if (FilteredIRAnchorsList.empty() || FilteredProfileAnchorList.empty())
+ return 0.0;
+
+ // Use the diff algorithm to find the LCS between IR and profile.
+ LocToLocMap MatchedAnchors =
+ longestCommonSequence(FilteredIRAnchorsList, FilteredProfileAnchorList);
+
+ return static_cast<float>(MatchedAnchors.size()) * 2 /
+ (FilteredIRAnchorsList.size() + FilteredProfileAnchorList.size());
+}
+
+bool SampleProfileMatcher::functionIsRenamedImpl(const Function &IRFunc,
+ const FunctionId &ProfFunc) {
+ float Similarity = checkFunctionSimilarity(IRFunc, ProfFunc);
+ LLVM_DEBUG(dbgs() << "The similarity between " << IRFunc.getName()
+ << "(IR) and " << ProfFunc << "(profile) is "
+ << format("%.2f", Similarity) << "\n");
+ return Similarity * 100 > FuncRenamingSimilarityThreshold;
+}
+
+bool SampleProfileMatcher::functionIsRenamed(const Function &IRFunc,
+ const FunctionId &ProfFunc) {
+ auto R = RenameDecisionCache.find({&IRFunc, ProfFunc});
+ if (R != RenameDecisionCache.end())
+ return R->second;
+
+ bool V = functionIsRenamedImpl(IRFunc, ProfFunc);
+ RenameDecisionCache[{&IRFunc, ProfFunc}] = V;
+ return V;
+}
+
+// Run function renaming matching on the profiled CFG edge to limit the matching
+// scope.
+void SampleProfileMatcher::runFuncRenamingMatchingOnProfile(
+ const StringMap<Function *> &IRNewFunctions, FunctionSamples &CallerFS,
+ FunctionMap &OldProfToNewSymbolMap) {
+ auto FindIRFunction = [&](const FunctionId &FName) {
+ // Function can be null if name has conflict, use optional to store the
+ // function pointer.
+ std::optional<Function *> F;
+
+ auto R = SymbolMap->find(FName);
+ if (R != SymbolMap->end())
+ F = R->second;
+
+ auto NewR = OldProfToNewSymbolMap.find(FName);
+ if (NewR != OldProfToNewSymbolMap.end())
+ F = NewR->second;
+
+ return F;
+ };
+
+ // Find the new callees from IR in the current caller scope.
+ std::vector<Function *> IRNewCallees;
+ auto Caller = FindIRFunction(CallerFS.getFunction());
+ if (Caller.has_value() && *Caller) {
+ // No callees for external function, skip the rename matching.
+ if ((*Caller)->isDeclaration())
+ return;
+ findIRNewCallees(**Caller, IRNewFunctions, IRNewCallees);
+ }
+
+ // Run renaming matching on CFG edge(caller-callee).
+ for (auto &CM :
+ const_cast<CallsiteSampleMap &>(CallerFS.getCallsiteSamples())) {
+ auto &CalleeMap = CM.second;
+ // Local container used to update the CallsiteSampleMap.
+ std::vector<std::pair<FunctionId, FunctionSamples *>> FSamplesToUpdate;
+ for (auto &CS : CalleeMap) {
+ auto &CalleeFS = CS.second;
+ auto ProfCallee = CalleeFS.getFunction();
+ auto ExistingIRCallee = FindIRFunction(ProfCallee);
+ // The profile callee is new, run renaming matching.
+ if (!ExistingIRCallee.has_value()) {
+ for (auto *IRCallee : IRNewCallees) {
+ if (functionIsRenamed(*IRCallee, ProfCallee)) {
+ FSamplesToUpdate.emplace_back(ProfCallee, &CalleeFS);
+ OldProfToNewSymbolMap[ProfCallee] = IRCallee;
+ // Update the profile in place so that the deeper level matching
+ // will find the IR function.
+ CalleeFS.setFunction(FunctionId(IRCallee->getName()));
+ LLVM_DEBUG(dbgs() << "Callee renaming is found in function "
+ << CallerFS.getFunction()
+ << ", changing profile name from " << ProfCallee
+ << " to " << IRCallee->getName() << "\n");
+ break;
+ }
+ }
+ } else {
+ // Apply the existing renaming result.
+ auto R = OldProfToNewSymbolMap.find(CalleeFS.getFunction());
+ if (R != OldProfToNewSymbolMap.end()) {
+ FunctionId IRNewCallee(R->second->getName());
+ assert(IRNewCallee != ProfCallee &&
+ "New callee symbol is not a new function");
+ FSamplesToUpdate.emplace_back(ProfCallee, &CalleeFS);
+ CalleeFS.setFunction(IRNewCallee);
+ LLVM_DEBUG(dbgs() << "Existing callee renaming is found in function "
+ << CallerFS.getFunction()
+ << ", changing profile name from " << ProfCallee
+ << " to " << IRNewCallee << "\n");
+ }
+ }
+ // Note that even there is no renaming in the current scope, there could
+ // be renaming in deeper callee scope, we need to traverse all the callee
+ // profiles.
+ runFuncRenamingMatchingOnProfile(IRNewFunctions, CalleeFS,
+ OldProfToNewSymbolMap);
+ }
+
+ // Update the CalleeMap using the new name and remove the old entry.
+ for (auto &P : FSamplesToUpdate) {
+ assert((P.first != P.second->getFunction()) &&
+ "Renamed function name should be different from the old map key");
+ CalleeMap[P.second->getFunction()] = *P.second;
+ CalleeMap.erase(P.first);
+ }
+ }
+}
+
+void SampleProfileMatcher::runFuncLevelMatching() {
+ if (!SalvageFunctionRenaming)
+ return;
+ assert(SymbolMap && "SymbolMap points to null");
----------------
WenleiHe wrote:
nit: SymbolMap points to null -> SymbolMap is null
https://github.com/llvm/llvm-project/pull/92151
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