[llvm-profgen] Loading binary functions from .symtab when DWARF info is incomplete

llvm/include/llvm/ProfileData/SampleProf.h

@@ -1214,13 +1214,19 @@ class FunctionSamples {
     // Note the sequence of the suffixes in the knownSuffixes array matters.
     // If suffix "A" is appended after the suffix "B", "A" should be in front
     // of "B" in knownSuffixes.
-    const char *KnownSuffixes[] = {LLVMSuffix, PartSuffix, UniqSuffix};
+    const SmallVector<StringRef> KnownSuffixes{LLVMSuffix, PartSuffix,
+                                               UniqSuffix};
+    return getCanonicalFnName(FnName, KnownSuffixes, Attr);
+  }
+
+  static StringRef getCanonicalFnName(StringRef FnName,
+                                      ArrayRef<StringRef> Suffixes,
+                                      StringRef Attr = "selected") {
     if (Attr == "" || Attr == "all")
       return FnName.split('.').first;
     if (Attr == "selected") {
       StringRef Cand(FnName);
-      for (const auto &Suf : KnownSuffixes) {
-        StringRef Suffix(Suf);
+      for (const auto Suffix : Suffixes) {
         // If the profile contains ".__uniq." suffix, don't strip the
         // suffix for names in the IR.
         if (Suffix == UniqSuffix && FunctionSamples::HasUniqSuffix)
@@ -1229,7 +1235,7 @@ class FunctionSamples {
         if (It == StringRef::npos)
           continue;
         auto Dit = Cand.rfind('.');
-        if (Dit == It + Suffix.size() - 1)
+        if (Dit == It || Dit == It + Suffix.size() - 1)
           Cand = Cand.substr(0, It);
       }
       return Cand;

llvm/test/tools/llvm-profgen/missing-dwarf.test

@@ -0,0 +1,37 @@
+; RUN: rm -rf %t
+; RUN: mkdir -p %t
+; RUN: cd %t
+
+; RUN: echo -e "1\n401120-40113b:1\n1\n40112f->401110:1" > %t.prof
+
+; Test --load-function-from-symbol=0
+; RUN: llvm-profgen --format=text --unsymbolized-profile=%t.prof --binary=%S/Inputs/missing-dwarf.exe --output=%t1 --fill-zero-for-all-funcs --show-detailed-warning --use-offset=0 --load-function-from-symbol=0 2>&1 | FileCheck %s --check-prefix=CHECK-NO-LOAD-SYMTAB
+
+; CHECK-NO-LOAD-SYMTAB:      warning: Loading of DWARF info completed, but no binary functions have been retrieved.
+
+; Test --load-function-from-symbol=1
+; RUN: llvm-profgen --format=text --unsymbolized-profile=%t.prof --binary=%S/Inputs/missing-dwarf.exe --output=%t2 --fill-zero-for-all-funcs --show-detailed-warning --use-offset=0 --load-function-from-symbol=1
+; RUN: FileCheck %s --input-file %t2 --check-prefix=CHECK-LOAD-SYMTAB
+
+; CHECK-LOAD-SYMTAB:      main:2:1
+; CHECK-LOAD-SYMTAB-NEXT:  1: 1
+; CHECK-LOAD-SYMTAB-NEXT:  2: 1 foo:1
+; CHECK-LOAD-SYMTAB-NEXT:  !CFGChecksum: 281479271677951
+; CHECK-LOAD-SYMTAB-NEXT: foo:0:0
+; CHECK-LOAD-SYMTAB-NEXT:  1: 0
+; CHECK-LOAD-SYMTAB-NEXT:  !CFGChecksum: 4294967295
+
+; Build instructions:
+; missing-dwarf.o:       clang -gsplit-dwarf=split -fdebug-compilation-dir=.  test.c   -fdebug-info-for-profiling  -fpseudo-probe-for-profiling  -O0 -g -o missing-dwarf.o -c
+; missing-dwarf.exe:     clang -fdebug-compilation-dir=.  missing-dwarf.o -o missing-dwarf.exe  -fdebug-info-for-profiling  -fpseudo-probe-for-profiling  -O0 -g
+
+; Source code:
+
+int foo() {
+  return 1;
+}
+
+int main() {
+  foo();
+  return 0;
+}

llvm/tools/llvm-profgen/PerfReader.cpp

@@ -1284,6 +1284,7 @@ void PerfScriptReader::warnInvalidRange() {
   uint64_t TotalRangeNum = 0;
   uint64_t InstNotBoundary = 0;
   uint64_t UnmatchedRange = 0;
+  uint64_t RecoveredRange = 0;
   uint64_t RangeCrossFunc = 0;
   uint64_t BogusRange = 0;
 
@@ -1309,6 +1310,9 @@ void PerfScriptReader::warnInvalidRange() {
       continue;
     }
 
+    if (FRange->Func->HasSymtabName)
+      RecoveredRange += I.second;
+
     if (EndAddress >= FRange->EndAddress) {
       RangeCrossFunc += I.second;
       WarnInvalidRange(StartAddress, EndAddress, RangeCrossFuncMsg);
@@ -1328,6 +1332,9 @@ void PerfScriptReader::warnInvalidRange() {
   emitWarningSummary(
       UnmatchedRange, TotalRangeNum,
       "of samples are from ranges that do not belong to any functions.");
+  emitWarningSummary(RecoveredRange, TotalRangeNum,
+                     "of samples are from ranges that belong to functions "
+                     "recovered from symbol table.");
   emitWarningSummary(
       RangeCrossFunc, TotalRangeNum,
       "of samples are from ranges that do cross function boundaries.");

llvm/tools/llvm-profgen/ProfileGenerator.cpp

@@ -723,7 +723,8 @@ void ProfileGenerator::populateBodySamplesForAllFunctions(
 }
 
 StringRef
-ProfileGeneratorBase::getCalleeNameForAddress(uint64_t TargetAddress) {
+ProfileGeneratorBase::getCalleeNameForAddress(uint64_t TargetAddress,
+                                              bool RestoreSymbolName) {
   // Get the function range by branch target if it's a call branch.
   auto *FRange = Binary->findFuncRangeForStartAddr(TargetAddress);
 
@@ -732,6 +733,15 @@ ProfileGeneratorBase::getCalleeNameForAddress(uint64_t TargetAddress) {
   if (!FRange || !FRange->IsFuncEntry)
     return StringRef();
 
+  if (RestoreSymbolName && FRange->Func->HasSymtabName) {
+    const AddressProbesMap &Address2ProbesMap = Binary->getAddress2ProbesMap();
+    for (const MCDecodedPseudoProbe &Probe :
+         Address2ProbesMap.find(TargetAddress)) {
+      if (const auto *ProbeDesc = Binary->getFuncDescForGUID(Probe.getGuid()))
+        return FunctionSamples::getCanonicalFnName(ProbeDesc->FuncName);
+    }
+  }
+
   return FunctionSamples::getCanonicalFnName(FRange->getFuncName());
 }
 
@@ -1352,7 +1362,7 @@ void CSProfileGenerator::populateBoundarySamplesWithProbes(
         getFunctionProfileForLeafProbe(CtxKey, CallProbe);
     FunctionProfile.addBodySamples(CallProbe->getIndex(), 0, Count);
     FunctionProfile.addTotalSamples(Count);
-    StringRef CalleeName = getCalleeNameForAddress(TargetAddress);
+    StringRef CalleeName = getCalleeNameForAddress(TargetAddress, true);
     if (CalleeName.size() == 0)
       continue;
     FunctionProfile.addCalledTargetSamples(CallProbe->getIndex(),

llvm/tools/llvm-profgen/ProfileGenerator.h

@@ -109,7 +109,8 @@ class ProfileGeneratorBase {
 
   bool filterAmbiguousProfile(FunctionSamples &FS);
 
-  StringRef getCalleeNameForAddress(uint64_t TargetAddress);
+  StringRef getCalleeNameForAddress(uint64_t TargetAddress,
+                                    bool RestoreSymbolName = false);
 
   void computeSummaryAndThreshold(SampleProfileMap &ProfileMap);
 

llvm/tools/llvm-profgen/ProfiledBinary.cpp

@@ -65,6 +65,13 @@ static cl::list<std::string> DisassembleFunctions(
              "names only. Only work with show-disassembly-only"),
     cl::cat(ProfGenCategory));
 
+static cl::opt<bool>
+    LoadFunctionFromSymbol("load-function-from-symbol", cl::init(true),
+                           cl::desc("Gather additional binary function info "
+                                    "from symbols (e.g. .symtab) in case "
+                                    "dwarf info is incomplete."),
+                           cl::cat(ProfGenCategory));
+
 static cl::opt<bool>
     KernelBinary("kernel",
                  cl::desc("Generate the profile for Linux kernel binary."),
@@ -257,6 +264,9 @@ void ProfiledBinary::load() {
   if (ShowDisassemblyOnly)
     decodePseudoProbe(Obj);
 
+  if (LoadFunctionFromSymbol && UsePseudoProbes)
+    loadSymbolsFromSymtab(Obj);
+
   // Disassemble the text sections.
   disassemble(Obj);
 
@@ -461,6 +471,11 @@ void ProfiledBinary::decodePseudoProbe(const ObjectFile *Obj) {
   } else {
     for (auto *F : ProfiledFunctions) {
       GuidFilter.insert(Function::getGUIDAssumingExternalLinkage(F->FuncName));
+      // Function may have different names in symbol table. Adding
+      // back all the GUIDs if possible
+      auto AltGUIDs = AlternativeFunctionGUIDs.equal_range(F);
+      for (const auto &[_, Func] : make_range(AltGUIDs))
+        GuidFilter.insert(Func);
       for (auto &Range : F->Ranges) {
         auto GUIDs = StartAddrToSymMap.equal_range(Range.first);
         for (const auto &[StartAddr, Func] : make_range(GUIDs))
@@ -604,13 +619,13 @@ bool ProfiledBinary::dissassembleSymbol(std::size_t SI, ArrayRef<uint8_t> Bytes,
       // Record potential call targets for tail frame inference later-on.
       if (InferMissingFrames && FRange) {
         uint64_t Target = 0;
-        MIA->evaluateBranch(Inst, Address, Size, Target);
+        bool Err = MIA->evaluateBranch(Inst, Address, Size, Target);
         if (MCDesc.isCall()) {
           // Indirect call targets are unknown at this point. Recording the
           // unknown target (zero) for further LBR-based refinement.
           MissingContextInferrer->CallEdges[Address].insert(Target);
         } else if (MCDesc.isUnconditionalBranch()) {
-          assert(Target &&
+          assert(Err &&
                  "target should be known for unconditional direct branch");
           // Any inter-function unconditional jump is considered tail call at
           // this point. This is not 100% accurate and could further be
@@ -820,6 +835,93 @@ void ProfiledBinary::populateSymbolAddressList(const ObjectFile *Obj) {
   }
 }
 
+void ProfiledBinary::loadSymbolsFromSymtab(const ObjectFile *Obj) {
+  // Load binary functions from symbol table when Debug info is incomplete.
+  // Strip the internal suffixes which are not reflected in the DWARF info.
+  const SmallVector<StringRef, 10> Suffixes(
+      {// Internal suffixes from CoroSplit pass
+       ".cleanup", ".destroy", ".resume",
+       // Internal suffixes from Bolt
+       ".cold", ".warm",
+       // Compiler/LTO internal
+       ".llvm.", ".part.", ".isra.", ".constprop.", ".lto_priv."});
+  StringRef FileName = Obj->getFileName();
+  for (const SymbolRef &Symbol : Obj->symbols()) {
+    const SymbolRef::Type Type = unwrapOrError(Symbol.getType(), FileName);
+    const uint64_t StartAddr = unwrapOrError(Symbol.getAddress(), FileName);
+    const StringRef Name = unwrapOrError(Symbol.getName(), FileName);
+    uint64_t Size = 0;
+    if (isa<ELFObjectFileBase>(Symbol.getObject())) {
+      ELFSymbolRef ElfSymbol(Symbol);
+      Size = ElfSymbol.getSize();
+    }
+
+    if (Size == 0 || Type != SymbolRef::ST_Function)
+      continue;
+
+    const uint64_t EndAddr = StartAddr + Size;
+    const StringRef SymName =
+        FunctionSamples::getCanonicalFnName(Name, Suffixes);
+    assert(StartAddr < EndAddr && StartAddr >= getPreferredBaseAddress());
+
+    auto Range = findFuncRange(StartAddr);
+    if (!Range) {
+      assert(findFuncRange(EndAddr - 1) == nullptr);
+      // Function from symbol table not found previously in DWARF, store ranges.
+      auto Ret = BinaryFunctions.emplace(SymName, BinaryFunction());
+      auto &Func = Ret.first->second;
+      if (Ret.second) {
+        Func.FuncName = Ret.first->first;
+        HashBinaryFunctions[MD5Hash(StringRef(SymName))] = &Func;
+      }
+
+      Func.HasSymtabName = true;
+      Func.Ranges.emplace_back(StartAddr, EndAddr);
+
+      auto R = StartAddrToFuncRangeMap.emplace(StartAddr, FuncRange());
+      FuncRange &FRange = R.first->second;
+
+      FRange.Func = &Func;
+      FRange.StartAddress = StartAddr;
+      FRange.EndAddress = EndAddr;
+
+    } else if (SymName != Range->getFuncName()) {
+      // Function range already found from DWARF, but the symbol name from
+      // symbol table is inconsistent with debug info. Log this discrepaency and
+      // the alternative function GUID.
+      if (ShowDetailedWarning)
+        WithColor::warning()
+            << "Conflicting name for symbol " << Name << " with range ("
+            << format("%8" PRIx64, StartAddr) << ", "
+            << format("%8" PRIx64, EndAddr) << ")"
+            << ", but the DWARF symbol " << Range->getFuncName()
+            << " indicates an overlapping range ("
+            << format("%8" PRIx64, Range->StartAddress) << ", "
+            << format("%8" PRIx64, Range->EndAddress) << ")\n";
+
+      assert(StartAddr == Range->StartAddress && EndAddr == Range->EndAddress &&
+             "Mismatched function range");
+
+      Range->Func->HasSymtabName = true;
+      AlternativeFunctionGUIDs.emplace(Range->Func,
+                                       MD5Hash(StringRef(SymName)));
+
+    } else if (StartAddr != Range->StartAddress &&
+               EndAddr != Range->EndAddress) {
+      // Function already found in DWARF, but the address range from symbol
+      // table conflicts/overlaps with the debug info.
+      WithColor::warning() << "Conflicting range for symbol " << Name
+                           << " with range (" << format("%8" PRIx64, StartAddr)
+                           << ", " << format("%8" PRIx64, EndAddr) << ")"
+                           << ", but the DWARF symbol " << Range->getFuncName()
+                           << " indicates another range ("
+                           << format("%8" PRIx64, Range->StartAddress) << ", "
+                           << format("%8" PRIx64, Range->EndAddress) << ")\n";
+      llvm_unreachable("invalid function range");
+    }
+  }
+}
+
 void ProfiledBinary::loadSymbolsFromDWARFUnit(DWARFUnit &CompilationUnit) {
   for (const auto &DieInfo : CompilationUnit.dies()) {
     llvm::DWARFDie Die(&CompilationUnit, &DieInfo);

llvm/tools/llvm-profgen/ProfiledBinary.h

@@ -76,6 +76,7 @@ struct BinaryFunction {
   StringRef FuncName;
   // End of range is an exclusive bound.
   RangesTy Ranges;
+  bool HasSymtabName = false;
 
   uint64_t getFuncSize() {
     uint64_t Sum = 0;
@@ -231,6 +232,11 @@ class ProfiledBinary {
   // GUID to symbol start address map
   DenseMap<uint64_t, uint64_t> SymbolStartAddrs;
 
+  // Binary function to GUID mapping that stores the alternative names in symbol
+  // table, despite the original name from DWARF info
+  std::unordered_multimap<const BinaryFunction *, uint64_t>
+      AlternativeFunctionGUIDs;
+
   // These maps are for temporary use of warning diagnosis.
   DenseSet<int64_t> AddrsWithMultipleSymbols;
   DenseSet<std::pair<uint64_t, uint64_t>> AddrsWithInvalidInstruction;
@@ -356,6 +362,9 @@ class ProfiledBinary {
   // Create symbol to its start address mapping.
   void populateSymbolAddressList(const object::ObjectFile *O);
 
+  // Load functions from its symbol table (when DWARF info is missing).
+  void loadSymbolsFromSymtab(const object::ObjectFile *O);
+
   // A function may be spilt into multiple non-continuous address ranges. We use
   // this to set whether start a function range is the real entry of the
   // function and also set false to the non-function label.