Updating branches/google/stable to r176857

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/google/stable@177040 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 389 insertions, 0 deletions

diff --git a/lib/Transforms/ObjCARC/ObjCARC.h b/lib/Transforms/ObjCARC/ObjCARC.h
new file mode 100644
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+++ b/lib/Transforms/ObjCARC/ObjCARC.h
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+//===- ObjCARC.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 defines common definitions/declarations used by the ObjC ARC
+/// Optimizer. ARC stands for Automatic Reference Counting and is a system for
+/// managing reference counts for objects in Objective C.
+///
+/// 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_SCALAR_OBJCARC_H
+#define LLVM_TRANSFORMS_SCALAR_OBJCARC_H
+
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/InstIterator.h"
+#include "llvm/Transforms/ObjCARC.h"
+#include "llvm/Transforms/Utils/Local.h"
+
+namespace llvm {
+class raw_ostream;
+}
+
+namespace llvm {
+namespace objcarc {
+
+/// \brief A handy option to enable/disable all ARC Optimizations.
+extern bool EnableARCOpts;
+
+/// \brief Test if the given module looks interesting to run ARC optimization
+/// on.
+static inline bool ModuleHasARC(const Module &M) {
+  return
+    M.getNamedValue("objc_retain") ||
+    M.getNamedValue("objc_release") ||
+    M.getNamedValue("objc_autorelease") ||
+    M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
+    M.getNamedValue("objc_retainBlock") ||
+    M.getNamedValue("objc_autoreleaseReturnValue") ||
+    M.getNamedValue("objc_autoreleasePoolPush") ||
+    M.getNamedValue("objc_loadWeakRetained") ||
+    M.getNamedValue("objc_loadWeak") ||
+    M.getNamedValue("objc_destroyWeak") ||
+    M.getNamedValue("objc_storeWeak") ||
+    M.getNamedValue("objc_initWeak") ||
+    M.getNamedValue("objc_moveWeak") ||
+    M.getNamedValue("objc_copyWeak") ||
+    M.getNamedValue("objc_retainedObject") ||
+    M.getNamedValue("objc_unretainedObject") ||
+    M.getNamedValue("objc_unretainedPointer");
+}
+
+/// \enum InstructionClass
+/// \brief A simple classification for instructions.
+enum InstructionClass {
+  IC_Retain,              ///< objc_retain
+  IC_RetainRV,            ///< objc_retainAutoreleasedReturnValue
+  IC_RetainBlock,         ///< objc_retainBlock
+  IC_Release,             ///< objc_release
+  IC_Autorelease,         ///< objc_autorelease
+  IC_AutoreleaseRV,       ///< objc_autoreleaseReturnValue
+  IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
+  IC_AutoreleasepoolPop,  ///< objc_autoreleasePoolPop
+  IC_NoopCast,            ///< objc_retainedObject, etc.
+  IC_FusedRetainAutorelease, ///< objc_retainAutorelease
+  IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
+  IC_LoadWeakRetained,    ///< objc_loadWeakRetained (primitive)
+  IC_StoreWeak,           ///< objc_storeWeak (primitive)
+  IC_InitWeak,            ///< objc_initWeak (derived)
+  IC_LoadWeak,            ///< objc_loadWeak (derived)
+  IC_MoveWeak,            ///< objc_moveWeak (derived)
+  IC_CopyWeak,            ///< objc_copyWeak (derived)
+  IC_DestroyWeak,         ///< objc_destroyWeak (derived)
+  IC_StoreStrong,         ///< objc_storeStrong (derived)
+  IC_CallOrUser,          ///< could call objc_release and/or "use" pointers
+  IC_Call,                ///< could call objc_release
+  IC_User,                ///< could "use" a pointer
+  IC_None                 ///< anything else
+};
+
+raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class);
+
+/// \brief Test if the given class is objc_retain or equivalent.
+static inline bool IsRetain(InstructionClass Class) {
+  return Class == IC_Retain ||
+         Class == IC_RetainRV;
+}
+
+/// \brief Test if the given class is objc_autorelease or equivalent.
+static inline bool IsAutorelease(InstructionClass Class) {
+  return Class == IC_Autorelease ||
+         Class == IC_AutoreleaseRV;
+}
+
+/// \brief Test if the given class represents instructions which return their
+/// argument verbatim.
+static inline bool IsForwarding(InstructionClass Class) {
+  // objc_retainBlock technically doesn't always return its argument
+  // verbatim, but it doesn't matter for our purposes here.
+  return Class == IC_Retain ||
+         Class == IC_RetainRV ||
+         Class == IC_Autorelease ||
+         Class == IC_AutoreleaseRV ||
+         Class == IC_RetainBlock ||
+         Class == IC_NoopCast;
+}
+
+/// \brief Test if the given class represents instructions which do nothing if
+/// passed a null pointer.
+static inline bool IsNoopOnNull(InstructionClass Class) {
+  return Class == IC_Retain ||
+         Class == IC_RetainRV ||
+         Class == IC_Release ||
+         Class == IC_Autorelease ||
+         Class == IC_AutoreleaseRV ||
+         Class == IC_RetainBlock;
+}
+
+/// \brief Test if the given class represents instructions which are always safe
+/// to mark with the "tail" keyword.
+static inline bool IsAlwaysTail(InstructionClass Class) {
+  // IC_RetainBlock may be given a stack argument.
+  return Class == IC_Retain ||
+         Class == IC_RetainRV ||
+         Class == IC_AutoreleaseRV;
+}
+
+/// \brief Test if the given class represents instructions which are never safe
+/// to mark with the "tail" keyword.
+static inline bool IsNeverTail(InstructionClass Class) {
+  /// It is never safe to tail call objc_autorelease since by tail calling
+  /// objc_autorelease, we also tail call -[NSObject autorelease] which supports
+  /// fast autoreleasing causing our object to be potentially reclaimed from the
+  /// autorelease pool which violates the semantics of __autoreleasing types in
+  /// ARC.
+  return Class == IC_Autorelease;
+}
+
+/// \brief Test if the given class represents instructions which are always safe
+/// to mark with the nounwind attribute.
+static inline bool IsNoThrow(InstructionClass Class) {
+  // objc_retainBlock is not nounwind because it calls user copy constructors
+  // which could theoretically throw.
+  return Class == IC_Retain ||
+         Class == IC_RetainRV ||
+         Class == IC_Release ||
+         Class == IC_Autorelease ||
+         Class == IC_AutoreleaseRV ||
+         Class == IC_AutoreleasepoolPush ||
+         Class == IC_AutoreleasepoolPop;
+}
+
+/// Test whether the given instruction can autorelease any pointer or cause an
+/// autoreleasepool pop.
+static inline bool
+CanInterruptRV(InstructionClass Class) {
+  switch (Class) {
+  case IC_AutoreleasepoolPop:
+  case IC_CallOrUser:
+  case IC_Call:
+  case IC_Autorelease:
+  case IC_AutoreleaseRV:
+  case IC_FusedRetainAutorelease:
+  case IC_FusedRetainAutoreleaseRV:
+    return true;
+  default:
+    return false;
+  }
+}
+
+/// \brief Determine if F is one of the special known Functions.  If it isn't,
+/// return IC_CallOrUser.
+InstructionClass GetFunctionClass(const Function *F);
+
+/// \brief Determine which objc runtime call instruction class V belongs to.
+///
+/// This is similar to GetInstructionClass except that it only detects objc
+/// runtime calls. This allows it to be faster.
+///
+static inline InstructionClass GetBasicInstructionClass(const Value *V) {
+  if (const CallInst *CI = dyn_cast<CallInst>(V)) {
+    if (const Function *F = CI->getCalledFunction())
+      return GetFunctionClass(F);
+    // Otherwise, be conservative.
+    return IC_CallOrUser;
+  }
+
+  // Otherwise, be conservative.
+  return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
+}
+
+/// \brief Determine what kind of construct V is.
+InstructionClass GetInstructionClass(const Value *V);
+
+/// \brief This is a wrapper around getUnderlyingObject which also knows how to
+/// look through objc_retain and objc_autorelease calls, which we know to return
+/// their argument verbatim.
+static inline const Value *GetUnderlyingObjCPtr(const Value *V) {
+  for (;;) {
+    V = GetUnderlyingObject(V);
+    if (!IsForwarding(GetBasicInstructionClass(V)))
+      break;
+    V = cast<CallInst>(V)->getArgOperand(0);
+  }
+
+  return V;
+}
+
+/// \brief This is a wrapper around Value::stripPointerCasts which also knows
+/// how to look through objc_retain and objc_autorelease calls, which we know to
+/// return their argument verbatim.
+static inline const Value *StripPointerCastsAndObjCCalls(const Value *V) {
+  for (;;) {
+    V = V->stripPointerCasts();
+    if (!IsForwarding(GetBasicInstructionClass(V)))
+      break;
+    V = cast<CallInst>(V)->getArgOperand(0);
+  }
+  return V;
+}
+
+/// \brief This is a wrapper around Value::stripPointerCasts which also knows
+/// how to look through objc_retain and objc_autorelease calls, which we know to
+/// return their argument verbatim.
+static inline Value *StripPointerCastsAndObjCCalls(Value *V) {
+  for (;;) {
+    V = V->stripPointerCasts();
+    if (!IsForwarding(GetBasicInstructionClass(V)))
+      break;
+    V = cast<CallInst>(V)->getArgOperand(0);
+  }
+  return V;
+}
+
+/// \brief Assuming the given instruction is one of the special calls such as
+/// objc_retain or objc_release, return the argument value, stripped of no-op
+/// casts and forwarding calls.
+static inline Value *GetObjCArg(Value *Inst) {
+  return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
+}
+
+static inline bool isNullOrUndef(const Value *V) {
+  return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
+}
+
+static inline bool isNoopInstruction(const Instruction *I) {
+  return isa<BitCastInst>(I) ||
+    (isa<GetElementPtrInst>(I) &&
+     cast<GetElementPtrInst>(I)->hasAllZeroIndices());
+}
+
+
+/// \brief Erase the given instruction.
+///
+/// Many ObjC calls return their argument verbatim,
+/// so if it's such a call and the return value has users, replace them with the
+/// argument value.
+///
+static inline void EraseInstruction(Instruction *CI) {
+  Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
+
+  bool Unused = CI->use_empty();
+
+  if (!Unused) {
+    // Replace the return value with the argument.
+    assert(IsForwarding(GetBasicInstructionClass(CI)) &&
+           "Can't delete non-forwarding instruction with users!");
+    CI->replaceAllUsesWith(OldArg);
+  }
+
+  CI->eraseFromParent();
+
+  if (Unused)
+    RecursivelyDeleteTriviallyDeadInstructions(OldArg);
+}
+
+/// \brief Test whether the given value is possible a retainable object pointer.
+static inline bool IsPotentialRetainableObjPtr(const Value *Op) {
+  // Pointers to static or stack storage are not valid retainable object
+  // pointers.
+  if (isa<Constant>(Op) || isa<AllocaInst>(Op))
+    return false;
+  // Special arguments can not be a valid retainable object pointer.
+  if (const Argument *Arg = dyn_cast<Argument>(Op))
+    if (Arg->hasByValAttr() ||
+        Arg->hasNestAttr() ||
+        Arg->hasStructRetAttr())
+      return false;
+  // Only consider values with pointer types.
+  //
+  // It seemes intuitive to exclude function pointer types as well, since
+  // functions are never retainable object pointers, however clang occasionally
+  // bitcasts retainable object pointers to function-pointer type temporarily.
+  PointerType *Ty = dyn_cast<PointerType>(Op->getType());
+  if (!Ty)
+    return false;
+  // Conservatively assume anything else is a potential retainable object
+  // pointer.
+  return true;
+}
+
+static inline bool IsPotentialRetainableObjPtr(const Value *Op,
+                                               AliasAnalysis &AA) {
+  // First make the rudimentary check.
+  if (!IsPotentialRetainableObjPtr(Op))
+    return false;
+
+  // Objects in constant memory are not reference-counted.
+  if (AA.pointsToConstantMemory(Op))
+    return false;
+
+  // Pointers in constant memory are not pointing to reference-counted objects.
+  if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
+    if (AA.pointsToConstantMemory(LI->getPointerOperand()))
+      return false;
+
+  // Otherwise assume the worst.
+  return true;
+}
+
+/// \brief Helper for GetInstructionClass. Determines what kind of construct CS
+/// is.
+static inline InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
+  for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+       I != E; ++I)
+    if (IsPotentialRetainableObjPtr(*I))
+      return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
+
+  return CS.onlyReadsMemory() ? IC_None : IC_Call;
+}
+
+/// \brief Return true if this value refers to a distinct and identifiable
+/// object.
+///
+/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
+/// special knowledge of ObjC conventions.
+static inline bool IsObjCIdentifiedObject(const Value *V) {
+  // Assume that call results and arguments have their own "provenance".
+  // Constants (including GlobalVariables) and Allocas are never
+  // reference-counted.
+  if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
+      isa<Argument>(V) || isa<Constant>(V) ||
+      isa<AllocaInst>(V))
+    return true;
+
+  if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
+    const Value *Pointer =
+      StripPointerCastsAndObjCCalls(LI->getPointerOperand());
+    if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
+      // A constant pointer can't be pointing to an object on the heap. It may
+      // be reference-counted, but it won't be deleted.
+      if (GV->isConstant())
+        return true;
+      StringRef Name = GV->getName();
+      // These special variables are known to hold values which are not
+      // reference-counted pointers.
+      if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
+          Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
+          Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
+          Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
+          Name.startswith("\01l_objc_msgSend_fixup_"))
+        return true;
+    }
+  }
+
+  return false;
+}
+
+} // end namespace objcarc
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_OBJCARC_H