[CodeGen][NPM] Update BranchFolderLegacy make tail merge configurable via flag

llvm/include/llvm/CodeGen/BranchFoldingPass.h

@@ -24,6 +24,9 @@ class BranchFolderPass : public PassInfoMixin<BranchFolderPass> {
     return MachineFunctionProperties().set(
         MachineFunctionProperties::Property::NoPHIs);
   }
+
+  void printPipeline(raw_ostream &OS,
+                     function_ref<StringRef(StringRef)> MapClassName2PassName);
 };
 
 } // namespace llvm

llvm/include/llvm/CodeGen/Passes.h

@@ -257,6 +257,8 @@ namespace llvm {
   /// branches.
   extern char &BranchFolderPassID;
 
+  MachineFunctionPass *createBranchFolderPass(bool EnableTailMerge);
+
   /// BranchRelaxation - This pass replaces branches that need to jump further
   /// than is supported by a branch instruction.
   extern char &BranchRelaxationPassID;

llvm/lib/CodeGen/BranchFolding.cpp

@@ -39,7 +39,6 @@
 #include "llvm/CodeGen/MachineSizeOpts.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetOpcodes.h"
-#include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/IR/DebugInfoMetadata.h"
@@ -90,18 +89,20 @@ namespace {
 
   /// BranchFolderPass - Wrap branch folder in a machine function pass.
 class BranchFolderLegacy : public MachineFunctionPass {
+  bool EnableTailMerge;
+
 public:
   static char ID;
 
-  explicit BranchFolderLegacy() : MachineFunctionPass(ID) {}
+  explicit BranchFolderLegacy(bool EnableTailMerge = true)
+      : MachineFunctionPass(ID), EnableTailMerge(EnableTailMerge) {}
 
   bool runOnMachineFunction(MachineFunction &MF) override;
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<MachineBlockFrequencyInfoWrapperPass>();
     AU.addRequired<MachineBranchProbabilityInfoWrapperPass>();
     AU.addRequired<ProfileSummaryInfoWrapperPass>();
-    AU.addRequired<TargetPassConfig>();
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 
@@ -144,15 +145,21 @@ PreservedAnalyses BranchFolderPass::run(MachineFunction &MF,
   return getMachineFunctionPassPreservedAnalyses();
 }
 
+void BranchFolderPass::printPipeline(
+    raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
+  OS << MapClassName2PassName(name());
+  if (EnableTailMerge)
+    OS << "<enable-tail-merge>";
+}
+
 bool BranchFolderLegacy::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(MF.getFunction()))
     return false;
 
-  TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
   // TailMerge can create jump into if branches that make CFG irreducible for
   // HW that requires structurized CFG.
-  bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
-                         PassConfig->getEnableTailMerge();
+  bool EnableTailMerge =
+      !MF.getTarget().requiresStructuredCFG() && this->EnableTailMerge;
   MBFIWrapper MBBFreqInfo(
       getAnalysis<MachineBlockFrequencyInfoWrapperPass>().getMBFI());
   BranchFolder Folder(
@@ -2080,3 +2087,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   ++NumHoist;
   return true;
 }
+
+MachineFunctionPass *llvm::createBranchFolderPass(bool EnableTailMerge = true) {
+  return new BranchFolderLegacy(EnableTailMerge);
+}

llvm/lib/CodeGen/TargetPassConfig.cpp

@@ -707,6 +707,10 @@ void TargetPassConfig::addPass(Pass *P) {
   // and shouldn't reference it.
   AnalysisID PassID = P->getPassID();
 
+  IdentifyingPassPtr TargetID = getPassSubstitution(PassID);
+  if (!overridePass(PassID, TargetID).isValid())
+    return;
+
   if (StartBefore == PassID && StartBeforeCount++ == StartBeforeInstanceNum)
     Started = true;
   if (StopBefore == PassID && StopBeforeCount++ == StopBeforeInstanceNum)
@@ -1514,7 +1518,7 @@ void TargetPassConfig::addMachineLateOptimization() {
   addPass(&MachineLateInstrsCleanupID);
 
   // Branch folding must be run after regalloc and prolog/epilog insertion.
-  addPass(&BranchFolderPassID);
+  addPass(createBranchFolderPass(getEnableTailMerge()));
 
   // Tail duplication.
   // Note that duplicating tail just increases code size and degrades