[AsmPrinter] Remove mbb-profile-dump flag (#76595)

Now that the work embedding PGO information in SHT_LLVM_BB_ADDR_MAP ELF
sections has landed, there is no longer a need to keep around the
mbb-profile-dump flag.

Author: boomanaiden154

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -236,10 +236,6 @@ class AsmPrinter : public MachineFunctionPass {
   /// split stack prologue.
   bool HasNoSplitStack = false;
 
-  /// Raw FDOstream for outputting machine basic block frequncies if the
-  /// --mbb-profile-dump flag is set for downstream cost modelling applications
-  std::unique_ptr<raw_fd_ostream> MBBProfileDumpFileOutput;
-
 protected:
   explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
 

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -134,13 +134,6 @@ using namespace llvm;
 
 #define DEBUG_TYPE "asm-printer"
 
-static cl::opt<std::string> BasicBlockProfileDump(
-    "mbb-profile-dump", cl::Hidden,
-    cl::desc("Basic block profile dump for external cost modelling. If "
-             "matching up BBs with afterwards, the compilation must be "
-             "performed with -basic-block-sections=labels. Enabling this "
-             "flag during in-process ThinLTO is not supported."));
-
 // This is a replication of fields of object::PGOAnalysisMap::Features. It
 // should match the order of the fields so that
 // `object::PGOAnalysisMap::Features::decode(PgoAnalysisMapFeatures.getBits())`
@@ -646,16 +639,6 @@ bool AsmPrinter::doInitialization(Module &M) {
     HI.Handler->beginModule(&M);
   }
 
-  if (!BasicBlockProfileDump.empty()) {
-    std::error_code PossibleFileError;
-    MBBProfileDumpFileOutput = std::make_unique<raw_fd_ostream>(
-        BasicBlockProfileDump, PossibleFileError);
-    if (PossibleFileError) {
-      M.getContext().emitError("Failed to open file for MBB Profile Dump: " +
-                               PossibleFileError.message() + "\n");
-    }
-  }
-
   return false;
 }
 
@@ -2026,40 +2009,6 @@ void AsmPrinter::emitFunctionBody() {
     OutStreamer->getCommentOS() << "-- End function\n";
 
   OutStreamer->addBlankLine();
-
-  // Output MBB ids, function names, and frequencies if the flag to dump
-  // MBB profile information has been set
-  if (MBBProfileDumpFileOutput && !MF->empty() &&
-      MF->getFunction().getEntryCount()) {
-    if (!MF->hasBBLabels()) {
-      MF->getContext().reportError(
-          SMLoc(),
-          "Unable to find BB labels for MBB profile dump. -mbb-profile-dump "
-          "must be called with -basic-block-sections=labels");
-    } else {
-      MachineBlockFrequencyInfo &MBFI =
-          getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI();
-      // The entry count and the entry basic block frequency aren't the same. We
-      // want to capture "absolute" frequencies, i.e. the frequency with which a
-      // MBB is executed when the program is executed. From there, we can derive
-      // Function-relative frequencies (divide by the value for the first MBB).
-      // We also have the information about frequency with which functions
-      // were called. This helps, for example, in a type of integration tests
-      // where we want to cross-validate the compiler's profile with a real
-      // profile.
-      // Using double precision because uint64 values used to encode mbb
-      // "frequencies" may be quite large.
-      const double EntryCount =
-          static_cast<double>(MF->getFunction().getEntryCount()->getCount());
-      for (const auto &MBB : *MF) {
-        const double MBBRelFreq = MBFI.getBlockFreqRelativeToEntryBlock(&MBB);
-        const double AbsMBBFreq = MBBRelFreq * EntryCount;
-        *MBBProfileDumpFileOutput.get()
-            << MF->getName() << "," << MBB.getBBID()->BaseID << ","
-            << AbsMBBFreq << "\n";
-      }
-    }
-  }
 }
 
 /// Compute the number of Global Variables that uses a Constant.