[InstrProf] Emit warnings when correlating lightweight profiles

[ellis]

Summary

Emit warnings when InstrProfCorrelator finds problems with debug info for lightweight instrumentation profile correlation. To prevent excessive printing, only emit the first 5 warnings.

In addition, remove a diagnostic about missing debug info in InstrProfiling.cpp. Some compiler-generated functions, e.g., __clang_call_terminate, does not emit debug info and will fail a build if -Werror is used. This warning is not actionable by the user and I have not seen non-compiler-generated functions fail this test.

[smeenai]

Is it possible to add a test case?

[phosek]

llvm/lib/ProfileData/InstrProfCorrelator.cpp

267

Could this be controlled by an option, with default value being 5, rather than hardcoding the value here?

[ellis]

Add flag ---max-debug-info-correlation-warnings and a test

[smeenai]

LGTM ... this seems like a straightforward enough improvement.

llvm/tools/llvm-profdata/llvm-profdata.cpp

3002 ↗

(On Diff #548002)

For these sorts of flags, 0 usually means unlimited, and it might be good to follow that pattern here. E.g. see --error-limit in LLD (and I'm pretty sure Clang works the same way).

[ellis]

Use 0 to mean unlimited warnings

llvm/lib/ProfileData/InstrProfCorrelator.cpp

 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
 #include "llvm/DebugInfo/DWARF/DWARFExpression.h"
 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
 #include "llvm/DebugInfo/DWARF/DWARFLocationExpression.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/WithColor.h"
 #include <optional>
 
 #define DEBUG_TYPE "correlator"
 
 using namespace llvm;
 
 /// Get the __llvm_prf_cnts section.
 Expected<object::SectionRef> getCountersSection(const object::ObjectFile &Obj) {
bool DwarfInstrProfCorrelator<IntPtrT>::isDIEOfProbe(const DWARFDie &Die) {
   if (const char *Name = Die.getName(DINameKind::ShortName))
     return StringRef(Name).startswith(getInstrProfCountersVarPrefix());
   return false;
 }
 
 template <class IntPtrT>
 void DwarfInstrProfCorrelator<IntPtrT>::correlateProfileDataImpl(
     InstrProfCorrelator::CorrelationData *Data) {
+  // The negation of the maximum number of warnings we would like to emit
+  int NumSuppressedWarnings = -5;
   auto maybeAddProbe = [&](DWARFDie Die) {
     if (!isDIEOfProbe(Die))
       return;
     std::optional<const char *> FunctionName;
     std::optional<uint64_t> CFGHash;
     std::optional<uint64_t> CounterPtr = getLocation(Die);
     auto FnDie = Die.getParent();
     auto FunctionPtr = dwarf::toAddress(FnDie.find(dwarf::DW_AT_low_pc));
for (const DWARFDie &Child : Die.children()) {
                      InstrProfCorrelator::CFGHashAttributeName) == 0) {
         CFGHash = AnnotationFormValue->getAsUnsignedConstant();
       } else if (AnnotationName.compare(
                      InstrProfCorrelator::NumCountersAttributeName) == 0) {
         NumCounters = AnnotationFormValue->getAsUnsignedConstant();
       }
     }
     if (!FunctionName || !CFGHash || !CounterPtr || !NumCounters) {
-      LLVM_DEBUG(dbgs() << "Incomplete DIE for probe\n\tFunctionName: "
-                        << FunctionName << "\n\tCFGHash: " << CFGHash
-                        << "\n\tCounterPtr: " << CounterPtr
-                        << "\n\tNumCounters: " << NumCounters);
+      if (++NumSuppressedWarnings < 1) {
+        WithColor::warning()
+            << "Incomplete DIE for function " << FunctionName
+            << ": CFGHash=" << CFGHash << "  CounterPtr=" << CounterPtr
+            << "  NumCounters=" << NumCounters << "\n";
         LLVM_DEBUG(Die.dump(dbgs()));
+      }
       return;
     }
     uint64_t CountersStart = this->Ctx->CountersSectionStart;
     uint64_t CountersEnd = this->Ctx->CountersSectionEnd;
     if (*CounterPtr < CountersStart || *CounterPtr >= CountersEnd) {
-      LLVM_DEBUG(
-          dbgs() << "CounterPtr out of range for probe\n\tFunction Name: "
-                 << FunctionName << "\n\tExpected: [0x"
-                 << Twine::utohexstr(CountersStart) << ", 0x"
-                 << Twine::utohexstr(CountersEnd) << ")\n\tActual: 0x"
-                 << Twine::utohexstr(*CounterPtr));
+      if (++NumSuppressedWarnings < 1) {
+        WithColor::warning()
+            << format("CounterPtr out of range for function %s: Actual=0x%x "
+                      "Expected=[0x%x, 0x%x)\n",
+                      *FunctionName, *CounterPtr, CountersStart, CountersEnd);
         LLVM_DEBUG(Die.dump(dbgs()));
+      }
       return;
     }
-    if (!FunctionPtr) {
-      LLVM_DEBUG(dbgs() << "Could not find address of " << *FunctionName
-                        << "\n");
+    if (!FunctionPtr && ++NumSuppressedWarnings < 1) {
+      WithColor::warning() << format("Could not find address of function %s\n",
+                                     *FunctionName);
       LLVM_DEBUG(Die.dump(dbgs()));
     }
     IntPtrT CounterOffset = *CounterPtr - CountersStart;
     if (Data) {
       InstrProfCorrelator::Probe P;
       P.FunctionName = *FunctionName;
       if (auto Name = FnDie.getName(DINameKind::LinkageName))
         P.LinkageName = Name;
auto maybeAddProbe = [&](DWARFDie Die) {
     }
   };
   for (auto &CU : DICtx->normal_units())
     for (const auto &Entry : CU->dies())
       maybeAddProbe(DWARFDie(CU.get(), &Entry));
   for (auto &CU : DICtx->dwo_units())
     for (const auto &Entry : CU->dies())
       maybeAddProbe(DWARFDie(CU.get(), &Entry));
+
+  if (NumSuppressedWarnings > 0)
+    WithColor::warning() << format("Suppressed %d additional warnings\n",
+                                   NumSuppressedWarnings);
 }

llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp

if (auto *SP = Fn->getSubprogram()) {
       auto *DICounter = DB.createGlobalVariableExpression(
           SP, CounterPtr->getName(), /*LinkageName=*/StringRef(), SP->getFile(),
           /*LineNo=*/0, DB.createUnspecifiedType("Profile Data Type"),
           CounterPtr->hasLocalLinkage(), /*IsDefined=*/true, /*Expr=*/nullptr,
           /*Decl=*/nullptr, /*TemplateParams=*/nullptr, /*AlignInBits=*/0,
           Annotations);
       CounterPtr->addDebugInfo(DICounter);
       DB.finalize();
-    } else {
-      std::string Msg = ("Missing debug info for function " + Fn->getName() +
-                         "; required for profile correlation.")
-                            .str();
-      Ctx.diagnose(
-          DiagnosticInfoPGOProfile(M->getName().data(), Msg, DS_Warning));
     }
   }
 
   auto *Int8PtrTy = Type::getInt8PtrTy(Ctx);
   // Allocate statically the array of pointers to value profile nodes for
   // the current function.
   Constant *ValuesPtrExpr = ConstantPointerNull::get(Int8PtrTy);
   uint64_t NS = 0;