[llvm] Make legacy FPPassManager more inheritable (PR #169475)

[Diana Picus via llvm-commits]

https://github.com/rovka updated https://github.com/llvm/llvm-project/pull/169475

>From 4731a1c6a0b6cac4bb2ae0bc8056d29f5a725976 Mon Sep 17 00:00:00 2001
From: Diana Picus <diana-magda.picus at amd.com>
Date: Fri, 3 Oct 2025 14:10:14 +0200
Subject: [PATCH] Make legacy FPPassManager more inheritable

Make it possible to inherit from the `FPPassManager` and override the
`runOnFunction` method. Also use the already virtual `getPassName` when
dumping the pass structure, so we get the correct name for subclasses.
---
 llvm/include/llvm/IR/LegacyPassManagers.h | 8 ++++++--
 llvm/lib/IR/LegacyPassManager.cpp         | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/IR/LegacyPassManagers.h b/llvm/include/llvm/IR/LegacyPassManagers.h
index d25bcafc9cc05..b1a2148f08894 100644
--- a/llvm/include/llvm/IR/LegacyPassManagers.h
+++ b/llvm/include/llvm/IR/LegacyPassManagers.h
@@ -461,7 +461,7 @@ class LLVM_ABI FPPassManager : public ModulePass, public PMDataManager {
 
   /// run - Execute all of the passes scheduled for execution.  Keep track of
   /// whether any of the passes modifies the module, and if so, return true.
-  bool runOnFunction(Function &F);
+  virtual bool runOnFunction(Function &F);
   bool runOnModule(Module &M) override;
 
   /// cleanup - After running all passes, clean up pass manager cache.
@@ -496,7 +496,7 @@ class LLVM_ABI FPPassManager : public ModulePass, public PMDataManager {
   // Print passes managed by this manager
   void dumpPassStructure(unsigned Offset) override;
 
-  StringRef getPassName() const override { return "Function Pass Manager"; }
+  StringRef getPassName() const override { return "FunctionPass Manager"; }
 
   FunctionPass *getContainedPass(unsigned N) {
     assert ( N < PassVector.size() && "Pass number out of range!");
@@ -507,6 +507,10 @@ class LLVM_ABI FPPassManager : public ModulePass, public PMDataManager {
   PassManagerType getPassManagerType() const override {
     return PMT_FunctionPassManager;
   }
+
+protected:
+  // So subclasses can pass their own ID.
+  explicit FPPassManager(char &ID) : ModulePass(ID) {}
 };
 }
 
diff --git a/llvm/lib/IR/LegacyPassManager.cpp b/llvm/lib/IR/LegacyPassManager.cpp
index 47a828842b481..00b8c68b28a92 100644
--- a/llvm/lib/IR/LegacyPassManager.cpp
+++ b/llvm/lib/IR/LegacyPassManager.cpp
@@ -1342,7 +1342,7 @@ void FPPassManager::cleanup() {
 char FPPassManager::ID = 0;
 /// Print passes managed by this manager
 void FPPassManager::dumpPassStructure(unsigned Offset) {
-  dbgs().indent(Offset*2) << "FunctionPass Manager\n";
+  dbgs().indent(Offset * 2) << getPassName() << '\n';
   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     FunctionPass *FP = getContainedPass(Index);
     FP->dumpPassStructure(Offset + 1);