[opt][profiling] Add -strip-profile option to opt tool, to remove profile information from IR

[nilanjana_basu]

Summary

Adding option to strip profile from IR output which can be useful for debugging PGO issues by comparing against non-PGO cases

llvm/include/llvm/IR/Instruction.h

public:
   void dropPoisonGeneratingFlags();
 
   /// Return true if this instruction has poison-generating metadata.
   bool hasPoisonGeneratingMetadata() const LLVM_READONLY;
 
   /// Drops metadata that may generate poison.
   void dropPoisonGeneratingMetadata();
 
+  /// Drops profile metadata
+  void dropProfMetadata();
+
   /// Return true if this instruction has poison-generating flags or metadata.
   bool hasPoisonGeneratingFlagsOrMetadata() const {
     return hasPoisonGeneratingFlags() || hasPoisonGeneratingMetadata();
   }
 
   /// Drops flags and metadata that may generate poison.
   void dropPoisonGeneratingFlagsAndMetadata() {
     dropPoisonGeneratingFlags();

llvm/include/llvm/IR/ProfDataUtils.h

 /// Retrieve the total of all weights from an instruction.
 ///
 /// \param I The instruction to extract the total weight from
 /// \param [out] TotalWeights input variable to fill with total weights
 /// \returns True on success with profile total weights filled in. False if no
 /// metadata was found.
 bool extractProfTotalWeight(const Instruction &I, uint64_t &TotalWeights);
 
+void StripProfileInfo(Module &M);
+
 } // namespace llvm
 #endif

llvm/lib/IR/Instruction.cpp

for (unsigned Idx = 0, NumSuccessors = Instruction::getNumSuccessors();
     if (getSuccessor(Idx) == OldBB)
       setSuccessor(Idx, NewBB);
 }
 
 Instruction *Instruction::cloneImpl() const {
   llvm_unreachable("Subclass of Instruction failed to implement cloneImpl");
 }
 
+void Instruction::dropProfMetadata() { eraseMetadata(LLVMContext::MD_prof); }
+
 void Instruction::swapProfMetadata() {
   MDNode *ProfileData = getBranchWeightMDNode(*this);
   if (!ProfileData || ProfileData->getNumOperands() != 3)
     return;
 
   // The first operand is the name. Fetch them backwards and build a new one.
   Metadata *Ops[] = {ProfileData->getOperand(0), ProfileData->getOperand(2),
                      ProfileData->getOperand(1)};

llvm/lib/IR/ProfDataUtils.cpp

 #include "llvm/IR/ProfDataUtils.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
 #include "llvm/Support/BranchProbability.h"
 #include "llvm/Support/CommandLine.h"
 
 using namespace llvm;
 
 namespace {
 
 // MD_prof nodes have the following layout
bool extractProfTotalWeight(const MDNode *ProfileData, uint64_t &TotalVal) {
   }
   return false;
 }
 
 bool extractProfTotalWeight(const Instruction &I, uint64_t &TotalVal) {
   return extractProfTotalWeight(I.getMetadata(LLVMContext::MD_prof), TotalVal);
 }
 
+void StripProfileInfo(Module &M) {
+  for (auto &GV : M.globals()) {
+    GV.eraseMetadata(LLVMContext::MD_prof);
+  }
+  for (Function &F : M) {
+    for (BasicBlock &BB : F) {
+      for (Instruction &I : llvm::make_early_inc_range(BB)) {
+        if (hasProfMD(I)) {
+          I.dropProfMetadata();
+        }
+      }
+    }
+    F.eraseMetadata(LLVMContext::MD_prof);
+  }
+}
+
 } // namespace llvm

llvm/tools/opt/opt.cpp

 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/LLVMRemarkStreamer.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/LegacyPassNameParser.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
+#include "llvm/IR/ProfDataUtils.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/IRReader/IRReader.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/LinkAllIR.h"
 #include "llvm/LinkAllPasses.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Passes/PassPlugin.h"
static cl::opt<bool>
     DisableDITypeMap("disable-debug-info-type-map",
                      cl::desc("Don't use a uniquing type map for debug info"));
 
 static cl::opt<bool>
 StripDebug("strip-debug",
            cl::desc("Strip debugger symbol info from translation unit"));
 
 static cl::opt<bool>
+    StripProfile("strip-profile",
+                 cl::desc("Strip profiler info from translation unit"));
+
+static cl::opt<bool>
     StripNamedMetadata("strip-named-metadata",
                        cl::desc("Strip module-level named metadata"));
 
 
 
 static cl::opt<bool>
     OptLevelO0("O0", cl::desc("Optimization level 0. Similar to clang -O0. "
                               "Use -passes='default<O0>' for the new PM"));
if (!M) {
     Err.print(argv[0], errs());
     return 1;
   }
 
   // Strip debug info before running the verifier.
   if (StripDebug)
     StripDebugInfo(*M);
 
+  // Strip profile info before running the verifier.
+  if (StripProfile)
+    StripProfileInfo(*M);
+
   // Erase module-level named metadata, if requested.
   if (StripNamedMetadata) {
     while (!M->named_metadata_empty()) {
       NamedMDNode *NMD = &*M->named_metadata_begin();
       M->eraseNamedMetadata(NMD);
     }
   }