[llvm] [CodeGen][NPM] Update BranchFolderLegacy make tail merge configurable via flag (PR #135277)

[Matt Arsenault via llvm-commits]

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@@ -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;
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arsenm wrote:

This should move to where the pass is added in TargetPassConfig, but I'll leave it up to you whether to do this now or later since it's already here 

https://github.com/llvm/llvm-project/pull/135277