1 //===- BarrierNoopPass.cpp - A barrier pass for the pass manager ----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // NOTE: DO NOT USE THIS IF AVOIDABLE 11 // 12 // This pass is a nonce pass intended to allow manipulation of the implicitly 13 // nesting pass manager. For example, it can be used to cause a CGSCC pass 14 // manager to be closed prior to running a new collection of function passes. 15 // 16 // FIXME: This is a huge HACK. This should be removed when the pass manager's 17 // nesting is made explicit instead of implicit. 18 // 19 //===----------------------------------------------------------------------===// 20 21 #include "llvm/Pass.h" 22 #include "llvm/Transforms/IPO.h" 23 using namespace llvm; 24 25 namespace { 26 /// \brief 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. 31 class BarrierNoop : public ModulePass { 32 public: 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 43 ModulePass *llvm::createBarrierNoopPass() { return new BarrierNoop(); } 44 45 char BarrierNoop::ID = 0; 46 INITIALIZE_PASS(BarrierNoop, "barrier", "A No-Op Barrier Pass", 47 false, false) 48
