LLVM  10.0.0svn
BarrierNoopPass.cpp
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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) {
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)
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents lattice values for constants.
Definition: AllocatorList.h:23
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:66
ModulePass * createBarrierNoopPass()
createBarrierNoopPass - This pass is purely a module pass barrier in a pass manager.
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:33
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:224
void initializeBarrierNoopPass(PassRegistry &)