1 //===- BarrierNoopPass.cpp - A barrier pass for the pass manager ----------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // NOTE: DO NOT USE THIS IF AVOIDABLE 10 // 11 // This pass is a nonce pass intended to allow manipulation of the implicitly 12 // nesting pass manager. For example, it can be used to cause a CGSCC pass 13 // manager to be closed prior to running a new collection of function passes. 14 // 15 // FIXME: This is a huge HACK. This should be removed when the pass manager's 16 // nesting is made explicit instead of implicit. 17 // 18 //===----------------------------------------------------------------------===// 19 20 #include "llvm/Pass.h" 21 #include "llvm/Transforms/IPO.h" 22 using namespace llvm; 23 24 namespace { 25 /// A nonce module pass used to place a barrier in a pass manager. 26 /// 27 /// There is no mechanism for ending a CGSCC pass manager once one is started. 28 /// This prevents extension points from having clear deterministic ordering 29 /// when they are phrased as non-module passes. 30 class BarrierNoop : public ModulePass { 31 public: 32 static char ID; // Pass identification. 33 34 BarrierNoop() : ModulePass(ID) { 35 initializeBarrierNoopPass(*PassRegistry::getPassRegistry()); 36 } 37 38 bool runOnModule(Module &M) override { return false; } 39 }; 40 } 41 42 ModulePass *llvm::createBarrierNoopPass() { return new BarrierNoop(); } 43 44 char BarrierNoop::ID = 0; 45 INITIALIZE_PASS(BarrierNoop, "barrier", "A No-Op Barrier Pass", 46 false, false) 47