Vendor import of llvm release_32 branch r168974 (effectively, 3.2 RC2):vendor/llvm/llvm-release_32-r168974

http://llvm.org/svn/llvm-project/llvm/branches/release_32@168974

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/Transforms/IPO/BarrierNoopPass.cpp b/lib/Transforms/IPO/BarrierNoopPass.cpp
new file mode 100644
index 000000000000..2e32240621f9
--- /dev/null
+++ b/lib/Transforms/IPO/BarrierNoopPass.cpp
@@ -0,0 +1,47 @@
+//===- BarrierNoopPass.cpp - A barrier pass for the pass manager ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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 {
+/// \brief 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) { return false; }
+};
+}
+
+ModulePass *llvm::createBarrierNoopPass() { return new BarrierNoop(); }
+
+char BarrierNoop::ID = 0;
+INITIALIZE_PASS(BarrierNoop, "barrier", "A No-Op Barrier Pass",
+                false, false)