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/InitializePasses.h" 21#include "llvm/Pass.h" 22#include "llvm/Transforms/IPO.h" 23using namespace llvm; 24 25namespace { 26/// A nonce module pass used to place a barrier in a pass manager. 27/// 28/// There is no mechanism for ending a CGSCC pass manager once one is started. 29/// This prevents extension points from having clear deterministic ordering 30/// when they are phrased as non-module passes. 31class BarrierNoop : public ModulePass { 32public: 33 static char ID; // Pass identification. 34 35 BarrierNoop() : ModulePass(ID) { 36 initializeBarrierNoopPass(*PassRegistry::getPassRegistry()); 37 } 38 39 bool runOnModule(Module &M) override { return false; } 40}; 41} 42 43ModulePass *llvm::createBarrierNoopPass() { return new BarrierNoop(); } 44 45char BarrierNoop::ID = 0; 46INITIALIZE_PASS(BarrierNoop, "barrier", "A No-Op Barrier Pass", 47 false, false) 48