[InstrProf][LWI] Allow entries with duplicate probe addresses

[ellis]

Summary

It turns out that storing CounterOffsets to prevent two data entries from pointing to the same probe is not useful. This negatively impacts memory and speed without much benefit. Also, this prevent the possibility of enabling ICF for instrumented functions.

[kyulee]

LGTM

[ellis]

Oops, this actually breaks a test and I need to think about this more. Closing.

llvm/include/llvm/ProfileData/InstrProfCorrelator.h

protected:
 
   void addProbe(StringRef FunctionName, uint64_t CFGHash, IntPtrT CounterOffset,
                 IntPtrT FunctionPtr, uint32_t NumCounters);
 
 private:
   InstrProfCorrelatorImpl(InstrProfCorrelatorKind Kind,
                           std::unique_ptr<InstrProfCorrelator::Context> Ctx)
       : InstrProfCorrelator(Kind, std::move(Ctx)){};
-  llvm::DenseSet<IntPtrT> CounterOffsets;
-
   // Byte-swap the value if necessary.
   template <class T> T maybeSwap(T Value) const {
     return Ctx->ShouldSwapBytes ? sys::getSwappedBytes(Value) : Value;
   }
 };
 
 /// DwarfInstrProfCorrelator - A child of InstrProfCorrelatorImpl that takes
 /// DWARF debug info as input to correlate profiles.

llvm/lib/ProfileData/InstrProfCorrelator.cpp

Error InstrProfCorrelatorImpl<IntPtrT>::correlateProfileData() {
   assert(Data.empty() && Names.empty() && NamesVec.empty());
   correlateProfileDataImpl();
   if (Data.empty() || NamesVec.empty())
     return make_error<InstrProfError>(
         instrprof_error::unable_to_correlate_profile,
         "could not find any profile metadata in debug info");
   auto Result =
       collectPGOFuncNameStrings(NamesVec, /*doCompression=*/false, Names);
-  CounterOffsets.clear();
   NamesVec.clear();
   return Result;
 }
 
 template <class IntPtrT>
 void InstrProfCorrelatorImpl<IntPtrT>::addProbe(StringRef FunctionName,
                                                 uint64_t CFGHash,
                                                 IntPtrT CounterOffset,
                                                 IntPtrT FunctionPtr,
                                                 uint32_t NumCounters) {
-  // Check if a probe was already added for this counter offset.
-  if (!CounterOffsets.insert(CounterOffset).second)
-    return;
   Data.push_back({
       maybeSwap<uint64_t>(IndexedInstrProf::ComputeHash(FunctionName)),
       maybeSwap<uint64_t>(CFGHash),
       // In this mode, CounterPtr actually stores the section relative address
       // of the counter.
       maybeSwap<IntPtrT>(CounterOffset),
       maybeSwap<IntPtrT>(FunctionPtr),
       // TODO: Value profiling is not yet supported.