Extracted ObjCARCContract from ObjCARCOpts into its own file.

This also required adding 2x headers Dependency Analysis.h/Provenance Analysis.h
and a .cpp file DependencyAnalysis.cpp to unentangle the dependencies inbetween
ObjCARCContract and ObjCARCOpts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173760 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/ObjCARC/DependencyAnalysis.h

@@ -0,0 +1,79 @@
+//===- DependencyAnalysis.h - ObjC ARC Optimization ---*- mode: c++ -*-----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file declares special dependency analysis routines used in Objective C
+/// ARC Optimizations.
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H
+#define LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H
+
+#include "llvm/ADT/SmallPtrSet.h"
+
+namespace llvm {
+  class BasicBlock;
+  class Instruction;
+  class Value;
+}
+
+namespace llvm {
+namespace objcarc {
+
+class ProvenanceAnalysis;
+
+/// \enum DependenceKind
+/// \brief Defines different dependence kinds among various ARC constructs.
+///
+/// There are several kinds of dependence-like concepts in use here.
+///
+enum DependenceKind {
+  NeedsPositiveRetainCount,
+  AutoreleasePoolBoundary,
+  CanChangeRetainCount,
+  RetainAutoreleaseDep,       ///< Blocks objc_retainAutorelease.
+  RetainAutoreleaseRVDep,     ///< Blocks objc_retainAutoreleaseReturnValue.
+  RetainRVDep                 ///< Blocks objc_retainAutoreleasedReturnValue.
+};
+
+void FindDependencies(DependenceKind Flavor,
+                      const Value *Arg,
+                      BasicBlock *StartBB, Instruction *StartInst,
+                      SmallPtrSet<Instruction *, 4> &DependingInstructions,
+                      SmallPtrSet<const BasicBlock *, 4> &Visited,
+                      ProvenanceAnalysis &PA);
+
+bool
+Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
+        ProvenanceAnalysis &PA);
+
+/// Test whether the given instruction can "use" the given pointer's object in a
+/// way that requires the reference count to be positive.
+bool
+CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
+       InstructionClass Class);
+
+/// Test whether the given instruction can result in a reference count
+/// modification (positive or negative) for the pointer's object.
+bool
+CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
+                 ProvenanceAnalysis &PA, InstructionClass Class);
+
+} // namespace objcarc
+} // namespace llvm
+
+#endif // LLVM_TRANSFORMS_OBJCARC_DEPEDENCYANALYSIS_H