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llvm-mirror/lib/Transforms/IPO/BarrierNoopPass.cpp
Chandler Carruth ae65e281f3 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00

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1.6 KiB
C++

//===- BarrierNoopPass.cpp - A barrier pass for the pass manager ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// NOTE: DO NOT USE THIS IF AVOIDABLE
//
// This pass is a nonce pass intended to allow manipulation of the implicitly
// nesting pass manager. For example, it can be used to cause a CGSCC pass
// manager to be closed prior to running a new collection of function passes.
//
// FIXME: This is a huge HACK. This should be removed when the pass manager's
// nesting is made explicit instead of implicit.
//
//===----------------------------------------------------------------------===//
#include "llvm/Pass.h"
#include "llvm/Transforms/IPO.h"
using namespace llvm;
namespace {
/// A nonce module pass used to place a barrier in a pass manager.
///
/// There is no mechanism for ending a CGSCC pass manager once one is started.
/// This prevents extension points from having clear deterministic ordering
/// when they are phrased as non-module passes.
class BarrierNoop : public ModulePass {
public:
static char ID; // Pass identification.
BarrierNoop() : ModulePass(ID) {
initializeBarrierNoopPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override { return false; }
};
}
ModulePass *llvm::createBarrierNoopPass() { return new BarrierNoop(); }
char BarrierNoop::ID = 0;
INITIALIZE_PASS(BarrierNoop, "barrier", "A No-Op Barrier Pass",
false, false)