[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)

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->FromSymtab)
+      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/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)
+    populateSymbolsFromBinary(Obj);
+
   // Disassemble the text sections.
   disassemble(Obj);
 
@@ -604,13 +614,13 @@ 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 +830,63 @@ void ProfiledBinary::populateSymbolAddressList(const ObjectFile *Obj) {
   }
 }
 
+void ProfiledBinary::populateSymbolsFromBinary(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, 6> Suffixes(
+      {
+        // Internal suffixes from CoroSplit pass
+        ".cleanup", ".destroy", ".resume",
+        // Internal suffixes from Bolt
+        ".cold", ".warm",
+        // Compiler internal
+        ".llvm.",
+      });
+  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 StringRef SymName =
+        FunctionSamples::getCanonicalFnName(Name, Suffixes);
+
+    auto Ret = BinaryFunctions.emplace(SymName, BinaryFunction());
+    auto &Func = Ret.first->second;
+    if (Ret.second) {
+      Func.FuncName = Ret.first->first;
+      Func.FromSymtab = true;
+      HashBinaryFunctions[MD5Hash(StringRef(SymName))] = &Func;
+    }
+
+    if (auto Range = findFuncRange(StartAddr)) {
+      if (Ret.second && Range->getFuncName() != SymName && ShowDetailedWarning)
+        WithColor::warning()
+            << "Conflicting symbol " << Name << " already exists in DWARF as "
+            << Range->getFuncName() << " at address " << format("%8" PRIx64, StartAddr)
+            << ". The DWARF indicates a range from " << format("%8" PRIx64, Range->StartAddress) << " to "
+            << format("%8" PRIx64, Range->EndAddress) << "\n";
+    } else {
+      // Store/Update Function Range from SymTab
+      Func.Ranges.emplace_back(StartAddr, StartAddr + Size);
+
+      auto R = StartAddrToFuncRangeMap.emplace(StartAddr, FuncRange());
+      FuncRange &FRange = R.first->second;
+      FRange.Func = &Func;
+      FRange.StartAddress = StartAddr;
+      FRange.EndAddress = StartAddr + Size;
+    }
+  }
+}
+
 void ProfiledBinary::loadSymbolsFromDWARFUnit(DWARFUnit &CompilationUnit) {
   for (const auto &DieInfo : CompilationUnit.dies()) {
     llvm::DWARFDie Die(&CompilationUnit, &DieInfo);
@@ -844,8 +911,10 @@ void ProfiledBinary::loadSymbolsFromDWARFUnit(DWARFUnit &CompilationUnit) {
     // BinaryFunction indexed by the name.
     auto Ret = BinaryFunctions.emplace(Name, BinaryFunction());
     auto &Func = Ret.first->second;
-    if (Ret.second)
+    if (Ret.second) {
       Func.FuncName = Ret.first->first;
+      Func.FromSymtab = false;
+    }
 
     for (const auto &Range : Ranges) {
       uint64_t StartAddress = Range.LowPC;

llvm/tools/llvm-profgen/ProfiledBinary.h

@@ -76,6 +76,7 @@ struct BinaryFunction {
   StringRef FuncName;
   // End of range is an exclusive bound.
   RangesTy Ranges;
+  bool FromSymtab;
 
   uint64_t getFuncSize() {
     uint64_t Sum = 0;
@@ -356,6 +357,9 @@ 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 populateSymbolsFromBinary(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.