[UnifyFunctionExitNodes] Remove unused getters, NFC

[dstenb]

Summary

The get{Return,Unwind,Unreachable}Block functions in
UnifyFunctionExitNodes have not been used for many years,
so just remove them.

[bjope]

Just hoping that those unused functions aren't used by some OOT project. But considering that the API is totally untested (and the unwind part isn't even visible any longer) I think this cleanup is motivated.

LGTM - but please fixup the stale comments first!

llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h

9–10

Stale comments, starting at "Additionally...".

9–10

Looks like this pass doesn't care about unwind? So this should probably say unreachable instead?

llvm/lib/Transforms/Utils/UnifyFunctionExitNodes.cpp

8–9

Maybe we could say "... at most one return instruction, and at most one unreachable instruction in them."

8–10

Stale comments, starting at "Additionally...".

[dstenb]

Thanks, and sorry for overlooking the comments!

llvm/include/llvm/Transforms/Utils/UnifyFunctionExitNodes.h

 //===-- UnifyFunctionExitNodes.h - Ensure fn's have one return --*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass is used to ensure that functions have at most one return and one
-// unwind instruction in them.  Additionally, it keeps track of which node is
-// the new exit node of the CFG.  If there are no return or unwind instructions
-// in the function, the getReturnBlock/getUnwindBlock methods will return a null
-// pointer.
+// unreachable instruction in them.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TRANSFORMS_UTILS_UNIFYFUNCTIONEXITNODES_H
 #define LLVM_TRANSFORMS_UTILS_UNIFYFUNCTIONEXITNODES_H
 
 #include "llvm/Pass.h"
 
 namespace llvm {
 
 class BasicBlock;
 
 struct UnifyFunctionExitNodes : public FunctionPass {
-  BasicBlock *ReturnBlock = nullptr;
-  BasicBlock *UnwindBlock = nullptr;
-  BasicBlock *UnreachableBlock;
-
 public:
   static char ID; // Pass identification, replacement for typeid
   UnifyFunctionExitNodes();
 
   // We can preserve non-critical-edgeness when we unify function exit nodes
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
-  // getReturn|Unwind|UnreachableBlock - Return the new single (or nonexistent)
-  // return, unwind, or unreachable  basic blocks in the CFG.
-  //
-  BasicBlock *getReturnBlock() const { return ReturnBlock; }
-  BasicBlock *getUnwindBlock() const { return UnwindBlock; }
-  BasicBlock *getUnreachableBlock() const { return UnreachableBlock; }
-
   bool runOnFunction(Function &F) override;
 };
 
 Pass *createUnifyFunctionExitNodesPass();
 
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_UTILS_UNIFYFUNCTIONEXITNODES_H

llvm/lib/Transforms/Utils/UnifyFunctionExitNodes.cpp

 //===- UnifyFunctionExitNodes.cpp - Make all functions have a single exit -===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
-// This pass is used to ensure that functions have at most one return
-// instruction in them.  Additionally, it keeps track of which node is the new
-// exit node of the CFG.  If there are no exit nodes in the CFG, the getExitNode
-// method will return a null pointer.
+// This pass is used to ensure that functions have at most one return and one
+// unreachable instruction in them.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Type.h"
bool UnifyFunctionExitNodes::runOnFunction(Function &F) {
   std::vector<BasicBlock*> UnreachableBlocks;
   for (BasicBlock &I : F)
     if (isa<ReturnInst>(I.getTerminator()))
       ReturningBlocks.push_back(&I);
     else if (isa<UnreachableInst>(I.getTerminator()))
       UnreachableBlocks.push_back(&I);
 
   // Then unreachable blocks.
-  if (UnreachableBlocks.empty()) {
-    UnreachableBlock = nullptr;
-  } else if (UnreachableBlocks.size() == 1) {
-    UnreachableBlock = UnreachableBlocks.front();
-  } else {
-    UnreachableBlock = BasicBlock::Create(F.getContext(),
+  if (UnreachableBlocks.size() > 1) {
+    BasicBlock *UnreachableBlock = BasicBlock::Create(F.getContext(),
                                           "UnifiedUnreachableBlock", &F);
     new UnreachableInst(F.getContext(), UnreachableBlock);
 
     for (BasicBlock *BB : UnreachableBlocks) {
       BB->getInstList().pop_back();  // Remove the unreachable inst.
       BranchInst::Create(UnreachableBlock, BB);
     }
   }
 
-  // Now handle return blocks.
-  if (ReturningBlocks.empty()) {
-    ReturnBlock = nullptr;
-    return false;                          // No blocks return
-  } else if (ReturningBlocks.size() == 1) {
-    ReturnBlock = ReturningBlocks.front(); // Already has a single return block
+  // There is nothing more to do if we do not have multiple return blocks.
+  if (ReturningBlocks.size() <= 1)
     return false;
-  }
 
   // Otherwise, we need to insert a new basic block into the function, add a PHI
   // nodes (if the function returns values), and convert all of the return
   // instructions into unconditional branches.
   //
   BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
                                                "UnifiedReturnBlock", &F);
 
for (BasicBlock *BB : ReturningBlocks) {
     // Add an incoming element to the PHI node for every return instruction that
     // is merging into this new block...
     if (PN)
       PN->addIncoming(BB->getTerminator()->getOperand(0), BB);
 
     BB->getInstList().pop_back();  // Remove the return insn
     BranchInst::Create(NewRetBlock, BB);
   }
-  ReturnBlock = NewRetBlock;
   return true;
 }