The ARC language-specific optimizer. Credit to Dan Gohman.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133108 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index 589d0a9..b98fbed 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -303,6 +303,10 @@
if (!DisableVerify)
PM.add(createVerifierPass());
+ // Simplify ObjC ARC code. This is done late because it makes re-optimization
+ // difficult.
+ PM.add(createObjCARCContractPass());
+
// Run loop strength reduction before anything else.
if (OptLevel != CodeGenOpt::None && !DisableLSR) {
PM.add(createLoopStrengthReducePass(getTargetLowering()));
diff --git a/lib/Transforms/Scalar/CMakeLists.txt b/lib/Transforms/Scalar/CMakeLists.txt
index fcf914f..c223da6 100644
--- a/lib/Transforms/Scalar/CMakeLists.txt
+++ b/lib/Transforms/Scalar/CMakeLists.txt
@@ -20,6 +20,7 @@
LoopUnswitch.cpp
LowerAtomic.cpp
MemCpyOptimizer.cpp
+ ObjCARC.cpp
Reassociate.cpp
Reg2Mem.cpp
SCCP.cpp
diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
new file mode 100644
index 0000000..e65e285
--- /dev/null
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -0,0 +1,3520 @@
+//===- ObjCARC.cpp - ObjC ARC Optimization --------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines ObjC ARC optimizations. ARC stands for
+// Automatic Reference Counting and is a system for managing reference counts
+// for objects in Objective C.
+//
+// The optimizations performed include elimination of redundant, partially
+// redundant, and inconsequential reference count operations, elimination of
+// redundant weak pointer operations, pattern-matching and replacement of
+// low-level operations into higher-level operations, and numerous minor
+// simplifications.
+//
+// This file also defines a simple ARC-aware AliasAnalysis.
+//
+// WARNING: This file knows about certain library functions. It recognizes them
+// by name, and hardwires knowedge 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.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "objc-arc"
+#include "llvm/Function.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+using namespace llvm;
+
+// A handy option to enable/disable all optimizations in this file.
+static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
+
+//===----------------------------------------------------------------------===//
+// Misc. Utilities
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// MapVector - An associative container with fast insertion-order
+ /// (deterministic) iteration over its elements. Plus the special
+ /// blot operation.
+ template<class KeyT, class ValueT>
+ class MapVector {
+ /// Map - Map keys to indices in Vector.
+ typedef DenseMap<KeyT, size_t> MapTy;
+ MapTy Map;
+
+ /// Vector - Keys and values.
+ typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
+ VectorTy Vector;
+
+ public:
+ typedef typename VectorTy::iterator iterator;
+ typedef typename VectorTy::const_iterator const_iterator;
+ iterator begin() { return Vector.begin(); }
+ iterator end() { return Vector.end(); }
+ const_iterator begin() const { return Vector.begin(); }
+ const_iterator end() const { return Vector.end(); }
+
+#ifdef XDEBUG
+ ~MapVector() {
+ assert(Vector.size() >= Map.size()); // May differ due to blotting.
+ for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
+ I != E; ++I) {
+ assert(I->second < Vector.size());
+ assert(Vector[I->second].first == I->first);
+ }
+ for (typename VectorTy::const_iterator I = Vector.begin(),
+ E = Vector.end(); I != E; ++I)
+ assert(!I->first ||
+ (Map.count(I->first) &&
+ Map[I->first] == size_t(I - Vector.begin())));
+ }
+#endif
+
+ ValueT &operator[](KeyT Arg) {
+ std::pair<typename MapTy::iterator, bool> Pair =
+ Map.insert(std::make_pair(Arg, size_t(0)));
+ if (Pair.second) {
+ Pair.first->second = Vector.size();
+ Vector.push_back(std::make_pair(Arg, ValueT()));
+ return Vector.back().second;
+ }
+ return Vector[Pair.first->second].second;
+ }
+
+ std::pair<iterator, bool>
+ insert(const std::pair<KeyT, ValueT> &InsertPair) {
+ std::pair<typename MapTy::iterator, bool> Pair =
+ Map.insert(std::make_pair(InsertPair.first, size_t(0)));
+ if (Pair.second) {
+ Pair.first->second = Vector.size();
+ Vector.push_back(InsertPair);
+ return std::make_pair(llvm::prior(Vector.end()), true);
+ }
+ return std::make_pair(Vector.begin() + Pair.first->second, false);
+ }
+
+ const_iterator find(KeyT Key) const {
+ typename MapTy::const_iterator It = Map.find(Key);
+ if (It == Map.end()) return Vector.end();
+ return Vector.begin() + It->second;
+ }
+
+ /// blot - This is similar to erase, but instead of removing the element
+ /// from the vector, it just zeros out the key in the vector. This leaves
+ /// iterators intact, but clients must be prepared for zeroed-out keys when
+ /// iterating.
+ void blot(KeyT Key) {
+ typename MapTy::iterator It = Map.find(Key);
+ if (It == Map.end()) return;
+ Vector[It->second].first = KeyT();
+ Map.erase(It);
+ }
+
+ void clear() {
+ Map.clear();
+ Vector.clear();
+ }
+ };
+}
+
+//===----------------------------------------------------------------------===//
+// ARC Utilities.
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// InstructionClass - 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_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
+ };
+}
+
+/// IsPotentialUse - Test whether the given value is possible a
+/// reference-counted pointer.
+static bool IsPotentialUse(const Value *Op) {
+ // Pointers to static or stack storage are not reference-counted pointers.
+ if (isa<Constant>(Op) || isa<AllocaInst>(Op))
+ return false;
+ // Special arguments are not reference-counted.
+ if (const Argument *Arg = dyn_cast<Argument>(Op))
+ if (Arg->hasByValAttr() ||
+ Arg->hasNestAttr() ||
+ Arg->hasStructRetAttr())
+ return false;
+ // Only consider values with pointer types, and not function pointers.
+ const PointerType *Ty = dyn_cast<PointerType>(Op->getType());
+ if (!Ty || isa<FunctionType>(Ty->getElementType()))
+ return false;
+ // Conservatively assume anything else is a potential use.
+ return true;
+}
+
+/// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind
+/// of construct CS is.
+static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I)
+ if (IsPotentialUse(*I))
+ return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
+
+ return CS.onlyReadsMemory() ? IC_None : IC_Call;
+}
+
+/// GetFunctionClass - Determine if F is one of the special known Functions.
+/// If it isn't, return IC_CallOrUser.
+static InstructionClass GetFunctionClass(const Function *F) {
+ Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
+
+ // No arguments.
+ if (AI == AE)
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
+ .Default(IC_CallOrUser);
+
+ // One argument.
+ const Argument *A0 = AI++;
+ if (AI == AE)
+ // Argument is a pointer.
+ if (const PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
+ const Type *ETy = PTy->getElementType();
+ // Argument is i8*.
+ if (ETy->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_retain", IC_Retain)
+ .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
+ .Case("objc_retainBlock", IC_RetainBlock)
+ .Case("objc_release", IC_Release)
+ .Case("objc_autorelease", IC_Autorelease)
+ .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
+ .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
+ .Case("objc_retainedObject", IC_NoopCast)
+ .Case("objc_unretainedObject", IC_NoopCast)
+ .Case("objc_unretainedPointer", IC_NoopCast)
+ .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
+ .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
+ .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
+ .Default(IC_CallOrUser);
+
+ // Argument is i8**
+ if (const PointerType *Pte = dyn_cast<PointerType>(ETy))
+ if (Pte->getElementType()->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
+ .Case("objc_loadWeak", IC_LoadWeak)
+ .Case("objc_destroyWeak", IC_DestroyWeak)
+ .Default(IC_CallOrUser);
+ }
+
+ // Two arguments, first is i8**.
+ const Argument *A1 = AI++;
+ if (AI == AE)
+ if (const PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
+ if (const PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
+ if (Pte->getElementType()->isIntegerTy(8))
+ if (const PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
+ const Type *ETy1 = PTy1->getElementType();
+ // Second argument is i8*
+ if (ETy1->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_storeWeak", IC_StoreWeak)
+ .Case("objc_initWeak", IC_InitWeak)
+ .Default(IC_CallOrUser);
+ // Second argument is i8**.
+ if (const PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
+ if (Pte1->getElementType()->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_moveWeak", IC_MoveWeak)
+ .Case("objc_copyWeak", IC_CopyWeak)
+ .Default(IC_CallOrUser);
+ }
+
+ // Anything else.
+ return IC_CallOrUser;
+}
+
+/// GetInstructionClass - Determine what kind of construct V is.
+static InstructionClass GetInstructionClass(const Value *V) {
+ if (const Instruction *I = dyn_cast<Instruction>(V)) {
+ // Any instruction other than bitcast and gep with a pointer operand have a
+ // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
+ // to a subsequent use, rather than using it themselves, in this sense.
+ // As a short cut, several other opcodes are known to have no pointer
+ // operands of interest. And ret is never followed by a release, so it's
+ // not interesting to examine.
+ switch (I->getOpcode()) {
+ case Instruction::Call: {
+ const CallInst *CI = cast<CallInst>(I);
+ // Check for calls to special functions.
+ if (const Function *F = CI->getCalledFunction()) {
+ InstructionClass Class = GetFunctionClass(F);
+ if (Class != IC_CallOrUser)
+ return Class;
+
+ // None of the intrinsic functions do objc_release. For intrinsics, the
+ // only question is whether or not they may be users.
+ switch (F->getIntrinsicID()) {
+ case 0: break;
+ case Intrinsic::bswap: case Intrinsic::ctpop:
+ case Intrinsic::ctlz: case Intrinsic::cttz:
+ case Intrinsic::returnaddress: case Intrinsic::frameaddress:
+ case Intrinsic::stacksave: case Intrinsic::stackrestore:
+ case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
+ // Don't let dbg info affect our results.
+ case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
+ // Short cut: Some intrinsics obviously don't use ObjC pointers.
+ return IC_None;
+ default:
+ for (Function::const_arg_iterator AI = F->arg_begin(),
+ AE = F->arg_end(); AI != AE; ++AI)
+ if (IsPotentialUse(AI))
+ return IC_User;
+ return IC_None;
+ }
+ }
+ return GetCallSiteClass(CI);
+ }
+ case Instruction::Invoke:
+ return GetCallSiteClass(cast<InvokeInst>(I));
+ case Instruction::BitCast:
+ case Instruction::GetElementPtr:
+ case Instruction::Select: case Instruction::PHI:
+ case Instruction::Ret: case Instruction::Br:
+ case Instruction::Switch: case Instruction::IndirectBr:
+ case Instruction::Alloca: case Instruction::VAArg:
+ case Instruction::Add: case Instruction::FAdd:
+ case Instruction::Sub: case Instruction::FSub:
+ case Instruction::Mul: case Instruction::FMul:
+ case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
+ case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
+ case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
+ case Instruction::And: case Instruction::Or: case Instruction::Xor:
+ case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
+ case Instruction::IntToPtr: case Instruction::FCmp:
+ case Instruction::FPTrunc: case Instruction::FPExt:
+ case Instruction::FPToUI: case Instruction::FPToSI:
+ case Instruction::UIToFP: case Instruction::SIToFP:
+ case Instruction::InsertElement: case Instruction::ExtractElement:
+ case Instruction::ShuffleVector:
+ case Instruction::ExtractValue:
+ break;
+ case Instruction::ICmp:
+ // Comparing a pointer with null, or any other constant, isn't an
+ // interesting use, because we don't care what the pointer points to, or
+ // about the values of any other dynamic reference-counted pointers.
+ if (IsPotentialUse(I->getOperand(1)))
+ return IC_User;
+ break;
+ default:
+ // For anything else, check all the operands.
+ for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
+ OI != OE; ++OI)
+ if (IsPotentialUse(*OI))
+ return IC_User;
+ }
+ }
+
+ // Otherwise, it's totally inert for ARC purposes.
+ return IC_None;
+}
+
+/// GetBasicInstructionClass - Determine what kind of construct V is. This is
+/// similar to GetInstructionClass except that it only detects objc runtine
+/// calls. This allows it to be faster.
+static 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 IC_User;
+}
+
+/// IsRetain - Test if the the given class is objc_retain or
+/// equivalent.
+static bool IsRetain(InstructionClass Class) {
+ return Class == IC_Retain ||
+ Class == IC_RetainRV;
+}
+
+/// IsAutorelease - Test if the the given class is objc_autorelease or
+/// equivalent.
+static bool IsAutorelease(InstructionClass Class) {
+ return Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV;
+}
+
+/// IsForwarding - Test if the given class represents instructions which return
+/// their argument verbatim.
+static 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;
+}
+
+/// IsNoopOnNull - Test if the given class represents instructions which do
+/// nothing if passed a null pointer.
+static bool IsNoopOnNull(InstructionClass Class) {
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_Release ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV ||
+ Class == IC_RetainBlock;
+}
+
+/// IsAlwaysTail - Test if the given class represents instructions which are
+/// always safe to mark with the "tail" keyword.
+static bool IsAlwaysTail(InstructionClass Class) {
+ // IC_RetainBlock may be given a stack argument.
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV;
+}
+
+/// IsNoThrow - Test if the given class represents instructions which are always
+/// safe to mark with the nounwind attribute..
+static bool IsNoThrow(InstructionClass Class) {
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_RetainBlock ||
+ Class == IC_Release ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV ||
+ Class == IC_AutoreleasepoolPush ||
+ Class == IC_AutoreleasepoolPop;
+}
+
+/// EraseInstruction - Erase the given instruction. 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 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);
+}
+
+/// GetUnderlyingObjCPtr - 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 const Value *GetUnderlyingObjCPtr(const Value *V) {
+ for (;;) {
+ V = GetUnderlyingObject(V);
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+
+ return V;
+}
+
+/// StripPointerCastsAndObjCCalls - 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 const Value *StripPointerCastsAndObjCCalls(const Value *V) {
+ for (;;) {
+ V = V->stripPointerCasts();
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+ return V;
+}
+
+/// StripPointerCastsAndObjCCalls - 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 Value *StripPointerCastsAndObjCCalls(Value *V) {
+ for (;;) {
+ V = V->stripPointerCasts();
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+ return V;
+}
+
+/// GetObjCArg - 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 Value *GetObjCArg(Value *Inst) {
+ return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
+}
+
+/// IsObjCIdentifiedObject - This is similar to AliasAnalysis'
+/// isObjCIdentifiedObject, except that it uses special knowledge of
+/// ObjC conventions...
+static 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)) {
+ 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;
+}
+
+/// FindSingleUseIdentifiedObject - This is similar to
+/// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value
+/// with multiple uses.
+static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
+ if (Arg->hasOneUse()) {
+ if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
+ return FindSingleUseIdentifiedObject(BC->getOperand(0));
+ if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
+ if (GEP->hasAllZeroIndices())
+ return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
+ if (IsForwarding(GetBasicInstructionClass(Arg)))
+ return FindSingleUseIdentifiedObject(
+ cast<CallInst>(Arg)->getArgOperand(0));
+ if (!IsObjCIdentifiedObject(Arg))
+ return 0;
+ return Arg;
+ }
+
+ // If we found an identifiable object but it has multiple uses, but they
+ // are trivial uses, we can still consider this to be a single-use
+ // value.
+ if (IsObjCIdentifiedObject(Arg)) {
+ for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
+ UI != UE; ++UI) {
+ const User *U = *UI;
+ if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
+ return 0;
+ }
+
+ return Arg;
+ }
+
+ return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// ARC AliasAnalysis.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Pass.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/Passes.h"
+
+namespace {
+ /// ObjCARCAliasAnalysis - This is a simple alias analysis
+ /// implementation that uses knowledge of ARC constructs to answer queries.
+ ///
+ /// TODO: This class could be generalized to know about other ObjC-specific
+ /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
+ /// even though their offsets are dynamic.
+ class ObjCARCAliasAnalysis : public ImmutablePass,
+ public AliasAnalysis {
+ public:
+ static char ID; // Class identification, replacement for typeinfo
+ ObjCARCAliasAnalysis() : ImmutablePass(ID) {
+ initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
+ }
+
+ private:
+ virtual void initializePass() {
+ InitializeAliasAnalysis(this);
+ }
+
+ /// getAdjustedAnalysisPointer - This method is used when a pass implements
+ /// an analysis interface through multiple inheritance. If needed, it
+ /// should override this to adjust the this pointer as needed for the
+ /// specified pass info.
+ virtual void *getAdjustedAnalysisPointer(const void *PI) {
+ if (PI == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual AliasResult alias(const Location &LocA, const Location &LocB);
+ virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
+ virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+ virtual ModRefBehavior getModRefBehavior(const Function *F);
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Location &Loc);
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2);
+ };
+} // End of anonymous namespace
+
+// Register this pass...
+char ObjCARCAliasAnalysis::ID = 0;
+INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
+ "ObjC-ARC-Based Alias Analysis", false, true, false)
+
+ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
+ return new ObjCARCAliasAnalysis();
+}
+
+void
+ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ AliasAnalysis::getAnalysisUsage(AU);
+}
+
+AliasAnalysis::AliasResult
+ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::alias(LocA, LocB);
+
+ // First, strip off no-ops, including ObjC-specific no-ops, and try making a
+ // precise alias query.
+ const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
+ const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
+ AliasResult Result =
+ AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
+ Location(SB, LocB.Size, LocB.TBAATag));
+ if (Result != MayAlias)
+ return Result;
+
+ // If that failed, climb to the underlying object, including climbing through
+ // ObjC-specific no-ops, and try making an imprecise alias query.
+ const Value *UA = GetUnderlyingObjCPtr(SA);
+ const Value *UB = GetUnderlyingObjCPtr(SB);
+ if (UA != SA || UB != SB) {
+ Result = AliasAnalysis::alias(Location(UA), Location(UB));
+ // We can't use MustAlias or PartialAlias results here because
+ // GetUnderlyingObjCPtr may return an offsetted pointer value.
+ if (Result == NoAlias)
+ return NoAlias;
+ }
+
+ // If that failed, fail. We don't need to chain here, since that's covered
+ // by the earlier precise query.
+ return MayAlias;
+}
+
+bool
+ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
+ bool OrLocal) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+
+ // First, strip off no-ops, including ObjC-specific no-ops, and try making
+ // a precise alias query.
+ const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
+ if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
+ OrLocal))
+ return true;
+
+ // If that failed, climb to the underlying object, including climbing through
+ // ObjC-specific no-ops, and try making an imprecise alias query.
+ const Value *U = GetUnderlyingObjCPtr(S);
+ if (U != S)
+ return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
+
+ // If that failed, fail. We don't need to chain here, since that's covered
+ // by the earlier precise query.
+ return false;
+}
+
+AliasAnalysis::ModRefBehavior
+ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ // We have nothing to do. Just chain to the next AliasAnalysis.
+ return AliasAnalysis::getModRefBehavior(CS);
+}
+
+AliasAnalysis::ModRefBehavior
+ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::getModRefBehavior(F);
+
+ switch (GetFunctionClass(F)) {
+ case IC_NoopCast:
+ return DoesNotAccessMemory;
+ default:
+ break;
+ }
+
+ return AliasAnalysis::getModRefBehavior(F);
+}
+
+AliasAnalysis::ModRefResult
+ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::getModRefInfo(CS, Loc);
+
+ switch (GetBasicInstructionClass(CS.getInstruction())) {
+ case IC_Retain:
+ case IC_RetainRV:
+ case IC_RetainBlock:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_NoopCast:
+ case IC_AutoreleasepoolPush:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ // These functions don't access any memory visible to the compiler.
+ return NoModRef;
+ default:
+ break;
+ }
+
+ return AliasAnalysis::getModRefInfo(CS, Loc);
+}
+
+AliasAnalysis::ModRefResult
+ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
+ // TODO: Theoretically we could check for dependencies between objc_* calls
+ // and OnlyAccessesArgumentPointees calls or other well-behaved calls.
+ return AliasAnalysis::getModRefInfo(CS1, CS2);
+}
+
+//===----------------------------------------------------------------------===//
+// ARC expansion.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/InstIterator.h"
+#include "llvm/Transforms/Scalar.h"
+
+namespace {
+ /// ObjCARCExpand - Early ARC transformations.
+ class ObjCARCExpand : public FunctionPass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool runOnFunction(Function &F);
+
+ public:
+ static char ID;
+ ObjCARCExpand() : FunctionPass(ID) {
+ initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCExpand::ID = 0;
+INITIALIZE_PASS(ObjCARCExpand,
+ "objc-arc-expand", "ObjC ARC expansion", false, false)
+
+Pass *llvm::createObjCARCExpandPass() {
+ return new ObjCARCExpand();
+}
+
+void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+}
+
+bool ObjCARCExpand::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ bool Changed = false;
+
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
+ Instruction *Inst = &*I;
+
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_Retain:
+ case IC_RetainRV:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ // These calls return their argument verbatim, as a low-level
+ // optimization. However, this makes high-level optimizations
+ // harder. Undo any uses of this optimization that the front-end
+ // emitted here. We'll redo them in a later pass.
+ Changed = true;
+ Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0));
+ break;
+ default:
+ break;
+ }
+ }
+
+ return Changed;
+}
+
+//===----------------------------------------------------------------------===//
+// ARC optimization.
+//===----------------------------------------------------------------------===//
+
+// TODO: On code like this:
+//
+// objc_retain(%x)
+// stuff_that_cannot_release()
+// objc_autorelease(%x)
+// stuff_that_cannot_release()
+// objc_retain(%x)
+// stuff_that_cannot_release()
+// objc_autorelease(%x)
+//
+// The second retain and autorelease can be deleted.
+
+// TODO: It should be possible to delete
+// objc_autoreleasePoolPush and objc_autoreleasePoolPop
+// pairs if nothing is actually autoreleased between them. Also, autorelease
+// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
+// after inlining) can be turned into plain release calls.
+
+// TODO: Critical-edge splitting. If the optimial insertion point is
+// a critical edge, the current algorithm has to fail, because it doesn't
+// know how to split edges. It should be possible to make the optimizer
+// think in terms of edges, rather than blocks, and then split critical
+// edges on demand.
+
+// TODO: OptimizeSequences could generalized to be Interprocedural.
+
+// TODO: Recognize that a bunch of other objc runtime calls have
+// non-escaping arguments and non-releasing arguments, and may be
+// non-autoreleasing.
+
+// TODO: Sink autorelease calls as far as possible. Unfortunately we
+// usually can't sink them past other calls, which would be the main
+// case where it would be useful.
+
+#include "llvm/GlobalAlias.h"
+#include "llvm/Module.h"
+#include "llvm/Constants.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/Statistic.h"
+
+STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
+STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
+STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
+STATISTIC(NumRets, "Number of return value forwarding "
+ "retain+autoreleaes eliminated");
+STATISTIC(NumRRs, "Number of retain+release paths eliminated");
+STATISTIC(NumPeeps, "Number of calls peephole-optimized");
+
+namespace {
+ /// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it
+ /// uses many of the same techniques, except it uses special ObjC-specific
+ /// reasoning about pointer relationships.
+ class ProvenanceAnalysis {
+ AliasAnalysis *AA;
+
+ typedef std::pair<const Value *, const Value *> ValuePairTy;
+ typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
+ CachedResultsTy CachedResults;
+
+ bool relatedCheck(const Value *A, const Value *B);
+ bool relatedSelect(const SelectInst *A, const Value *B);
+ bool relatedPHI(const PHINode *A, const Value *B);
+
+ // Do not implement.
+ void operator=(const ProvenanceAnalysis &);
+ ProvenanceAnalysis(const ProvenanceAnalysis &);
+
+ public:
+ ProvenanceAnalysis() {}
+
+ void setAA(AliasAnalysis *aa) { AA = aa; }
+
+ AliasAnalysis *getAA() const { return AA; }
+
+ bool related(const Value *A, const Value *B);
+
+ void clear() {
+ CachedResults.clear();
+ }
+ };
+}
+
+bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
+ // If the values are Selects with the same condition, we can do a more precise
+ // check: just check for relations between the values on corresponding arms.
+ if (const SelectInst *SB = dyn_cast<SelectInst>(B))
+ if (A->getCondition() == SB->getCondition()) {
+ if (related(A->getTrueValue(), SB->getTrueValue()))
+ return true;
+ if (related(A->getFalseValue(), SB->getFalseValue()))
+ return true;
+ return false;
+ }
+
+ // Check both arms of the Select node individually.
+ if (related(A->getTrueValue(), B))
+ return true;
+ if (related(A->getFalseValue(), B))
+ return true;
+
+ // The arms both checked out.
+ return false;
+}
+
+bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
+ // If the values are PHIs in the same block, we can do a more precise as well
+ // as efficient check: just check for relations between the values on
+ // corresponding edges.
+ if (const PHINode *PNB = dyn_cast<PHINode>(B))
+ if (PNB->getParent() == A->getParent()) {
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
+ if (related(A->getIncomingValue(i),
+ PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
+ return true;
+ return false;
+ }
+
+ // Check each unique source of the PHI node against B.
+ SmallPtrSet<const Value *, 4> UniqueSrc;
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
+ const Value *PV1 = A->getIncomingValue(i);
+ if (UniqueSrc.insert(PV1) && related(PV1, B))
+ return true;
+ }
+
+ // All of the arms checked out.
+ return false;
+}
+
+/// isStoredObjCPointer - Test if the value of P, or any value covered by its
+/// provenance, is ever stored within the function (not counting callees).
+static bool isStoredObjCPointer(const Value *P) {
+ SmallPtrSet<const Value *, 8> Visited;
+ SmallVector<const Value *, 8> Worklist;
+ Worklist.push_back(P);
+ Visited.insert(P);
+ do {
+ P = Worklist.pop_back_val();
+ for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
+ UI != UE; ++UI) {
+ const User *Ur = *UI;
+ if (isa<StoreInst>(Ur)) {
+ if (UI.getOperandNo() == 0)
+ // The pointer is stored.
+ return true;
+ // The pointed is stored through.
+ continue;
+ }
+ if (isa<CallInst>(Ur))
+ // The pointer is passed as an argument, ignore this.
+ continue;
+ if (isa<PtrToIntInst>(P))
+ // Assume the worst.
+ return true;
+ if (Visited.insert(Ur))
+ Worklist.push_back(Ur);
+ }
+ } while (!Worklist.empty());
+
+ // Everything checked out.
+ return false;
+}
+
+bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
+ // Skip past provenance pass-throughs.
+ A = GetUnderlyingObjCPtr(A);
+ B = GetUnderlyingObjCPtr(B);
+
+ // Quick check.
+ if (A == B)
+ return true;
+
+ // Ask regular AliasAnalysis, for a first approximation.
+ switch (AA->alias(A, B)) {
+ case AliasAnalysis::NoAlias:
+ return false;
+ case AliasAnalysis::MustAlias:
+ case AliasAnalysis::PartialAlias:
+ return true;
+ case AliasAnalysis::MayAlias:
+ break;
+ }
+
+ bool AIsIdentified = IsObjCIdentifiedObject(A);
+ bool BIsIdentified = IsObjCIdentifiedObject(B);
+
+ // An ObjC-Identified object can't alias a load if it is never locally stored.
+ if (AIsIdentified) {
+ if (BIsIdentified) {
+ // If both pointers have provenance, they can be directly compared.
+ if (A != B)
+ return false;
+ } else {
+ if (isa<LoadInst>(B))
+ return isStoredObjCPointer(A);
+ }
+ } else {
+ if (BIsIdentified && isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ }
+
+ // Special handling for PHI and Select.
+ if (const PHINode *PN = dyn_cast<PHINode>(A))
+ return relatedPHI(PN, B);
+ if (const PHINode *PN = dyn_cast<PHINode>(B))
+ return relatedPHI(PN, A);
+ if (const SelectInst *S = dyn_cast<SelectInst>(A))
+ return relatedSelect(S, B);
+ if (const SelectInst *S = dyn_cast<SelectInst>(B))
+ return relatedSelect(S, A);
+
+ // Conservative.
+ return true;
+}
+
+bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
+ // Begin by inserting a conservative value into the map. If the insertion
+ // fails, we have the answer already. If it succeeds, leave it there until we
+ // compute the real answer to guard against recursive queries.
+ if (A > B) std::swap(A, B);
+ std::pair<CachedResultsTy::iterator, bool> Pair =
+ CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
+ if (!Pair.second)
+ return Pair.first->second;
+
+ bool Result = relatedCheck(A, B);
+ CachedResults[ValuePairTy(A, B)] = Result;
+ return Result;
+}
+
+namespace {
+ // Sequence - A sequence of states that a pointer may go through in which an
+ // objc_retain and objc_release are actually needed.
+ enum Sequence {
+ S_None,
+ S_Retain, ///< objc_retain(x)
+ S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
+ S_Use, ///< any use of x
+ S_Stop, ///< like S_Release, but code motion is stopped
+ S_Release, ///< objc_release(x)
+ S_MovableRelease ///< objc_release(x), !clang.imprecise_release
+ };
+}
+
+static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
+ // The easy cases.
+ if (A == B)
+ return A;
+ if (A == S_None || B == S_None)
+ return S_None;
+
+ // Note that we can't merge S_CanRelease and S_Use.
+ if (A > B) std::swap(A, B);
+ if (TopDown) {
+ // Choose the side which is further along in the sequence.
+ if (A == S_Retain && (B == S_CanRelease || B == S_Use))
+ return B;
+ } else {
+ // Choose the side which is further along in the sequence.
+ if ((A == S_Use || A == S_CanRelease) &&
+ (B == S_Release || B == S_Stop || B == S_MovableRelease))
+ return A;
+ // If both sides are releases, choose the more conservative one.
+ if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
+ return A;
+ if (A == S_Release && B == S_MovableRelease)
+ return A;
+ }
+
+ return S_None;
+}
+
+namespace {
+ /// RRInfo - Unidirectional information about either a
+ /// retain-decrement-use-release sequence or release-use-decrement-retain
+ /// reverese sequence.
+ struct RRInfo {
+ /// KnownIncremented - After an objc_retain, the reference count of the
+ /// referenced object is known to be positive. Similarly, before an
+ /// objc_release, the reference count of the referenced object is known to
+ /// be positive. If there are retain-release pairs in code regions where the
+ /// retain count is known to be positive, they can be eliminated, regardless
+ /// of any side effects between them.
+ bool KnownIncremented;
+
+ /// IsRetainBlock - True if the Calls are objc_retainBlock calls (as
+ /// opposed to objc_retain calls).
+ bool IsRetainBlock;
+
+ /// IsTailCallRelease - True of the objc_release calls are all marked
+ /// with the "tail" keyword.
+ bool IsTailCallRelease;
+
+ /// ReleaseMetadata - If the Calls are objc_release calls and they all have
+ /// a clang.imprecise_release tag, this is the metadata tag.
+ MDNode *ReleaseMetadata;
+
+ /// Calls - For a top-down sequence, the set of objc_retains or
+ /// objc_retainBlocks. For bottom-up, the set of objc_releases.
+ SmallPtrSet<Instruction *, 2> Calls;
+
+ /// ReverseInsertPts - The set of optimal insert positions for
+ /// moving calls in the opposite sequence.
+ SmallPtrSet<Instruction *, 2> ReverseInsertPts;
+
+ RRInfo() :
+ KnownIncremented(false), IsRetainBlock(false), IsTailCallRelease(false),
+ ReleaseMetadata(0) {}
+
+ void clear();
+ };
+}
+
+void RRInfo::clear() {
+ KnownIncremented = false;
+ IsRetainBlock = false;
+ IsTailCallRelease = false;
+ ReleaseMetadata = 0;
+ Calls.clear();
+ ReverseInsertPts.clear();
+}
+
+namespace {
+ /// PtrState - This class summarizes several per-pointer runtime properties
+ /// which are propogated through the flow graph.
+ class PtrState {
+ /// RefCount - The known minimum number of reference count increments.
+ unsigned RefCount;
+
+ /// Seq - The current position in the sequence.
+ Sequence Seq;
+
+ public:
+ /// RRI - Unidirectional information about the current sequence.
+ /// TODO: Encapsulate this better.
+ RRInfo RRI;
+
+ PtrState() : RefCount(0), Seq(S_None) {}
+
+ void IncrementRefCount() {
+ if (RefCount != UINT_MAX) ++RefCount;
+ }
+
+ void DecrementRefCount() {
+ if (RefCount != 0) --RefCount;
+ }
+
+ void ClearRefCount() {
+ RefCount = 0;
+ }
+
+ bool IsKnownIncremented() const {
+ return RefCount > 0;
+ }
+
+ void SetSeq(Sequence NewSeq) {
+ Seq = NewSeq;
+ }
+
+ void SetSeqToRelease(MDNode *M) {
+ if (Seq == S_None || Seq == S_Use) {
+ Seq = M ? S_MovableRelease : S_Release;
+ RRI.ReleaseMetadata = M;
+ } else if (Seq != S_MovableRelease || RRI.ReleaseMetadata != M) {
+ Seq = S_Release;
+ RRI.ReleaseMetadata = 0;
+ }
+ }
+
+ Sequence GetSeq() const {
+ return Seq;
+ }
+
+ void ClearSequenceProgress() {
+ Seq = S_None;
+ RRI.clear();
+ }
+
+ void Merge(const PtrState &Other, bool TopDown);
+ };
+}
+
+void
+PtrState::Merge(const PtrState &Other, bool TopDown) {
+ Seq = MergeSeqs(Seq, Other.Seq, TopDown);
+ RefCount = std::min(RefCount, Other.RefCount);
+
+ // We can't merge a plain objc_retain with an objc_retainBlock.
+ if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
+ Seq = S_None;
+
+ if (Seq == S_None) {
+ RRI.clear();
+ } else {
+ // Conservatively merge the ReleaseMetadata information.
+ if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
+ RRI.ReleaseMetadata = 0;
+
+ RRI.KnownIncremented = RRI.KnownIncremented && Other.RRI.KnownIncremented;
+ RRI.IsTailCallRelease = RRI.IsTailCallRelease && Other.RRI.IsTailCallRelease;
+ RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
+ RRI.ReverseInsertPts.insert(Other.RRI.ReverseInsertPts.begin(),
+ Other.RRI.ReverseInsertPts.end());
+ }
+}
+
+namespace {
+ /// BBState - Per-BasicBlock state.
+ class BBState {
+ /// TopDownPathCount - The number of unique control paths from the entry
+ /// which can reach this block.
+ unsigned TopDownPathCount;
+
+ /// BottomUpPathCount - The number of unique control paths to exits
+ /// from this block.
+ unsigned BottomUpPathCount;
+
+ /// MapTy - A type for PerPtrTopDown and PerPtrBottomUp.
+ typedef MapVector<const Value *, PtrState> MapTy;
+
+ /// PerPtrTopDown - The top-down traversal uses this to record information
+ /// known about a pointer at the bottom of each block.
+ MapTy PerPtrTopDown;
+
+ /// PerPtrBottomUp - The bottom-up traversal uses this to record information
+ /// known about a pointer at the top of each block.
+ MapTy PerPtrBottomUp;
+
+ public:
+ BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
+
+ typedef MapTy::iterator ptr_iterator;
+ typedef MapTy::const_iterator ptr_const_iterator;
+
+ ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
+ ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
+ ptr_const_iterator top_down_ptr_begin() const {
+ return PerPtrTopDown.begin();
+ }
+ ptr_const_iterator top_down_ptr_end() const {
+ return PerPtrTopDown.end();
+ }
+
+ ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
+ ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
+ ptr_const_iterator bottom_up_ptr_begin() const {
+ return PerPtrBottomUp.begin();
+ }
+ ptr_const_iterator bottom_up_ptr_end() const {
+ return PerPtrBottomUp.end();
+ }
+
+ /// SetAsEntry - Mark this block as being an entry block, which has one
+ /// path from the entry by definition.
+ void SetAsEntry() { TopDownPathCount = 1; }
+
+ /// SetAsExit - Mark this block as being an exit block, which has one
+ /// path to an exit by definition.
+ void SetAsExit() { BottomUpPathCount = 1; }
+
+ PtrState &getPtrTopDownState(const Value *Arg) {
+ return PerPtrTopDown[Arg];
+ }
+
+ PtrState &getPtrBottomUpState(const Value *Arg) {
+ return PerPtrBottomUp[Arg];
+ }
+
+ void clearBottomUpPointers() {
+ PerPtrTopDown.clear();
+ }
+
+ void clearTopDownPointers() {
+ PerPtrTopDown.clear();
+ }
+
+ void InitFromPred(const BBState &Other);
+ void InitFromSucc(const BBState &Other);
+ void MergePred(const BBState &Other);
+ void MergeSucc(const BBState &Other);
+
+ /// GetAllPathCount - Return the number of possible unique paths from an
+ /// entry to an exit which pass through this block. This is only valid
+ /// after both the top-down and bottom-up traversals are complete.
+ unsigned GetAllPathCount() const {
+ return TopDownPathCount * BottomUpPathCount;
+ }
+ };
+}
+
+void BBState::InitFromPred(const BBState &Other) {
+ PerPtrTopDown = Other.PerPtrTopDown;
+ TopDownPathCount = Other.TopDownPathCount;
+}
+
+void BBState::InitFromSucc(const BBState &Other) {
+ PerPtrBottomUp = Other.PerPtrBottomUp;
+ BottomUpPathCount = Other.BottomUpPathCount;
+}
+
+/// MergePred - The top-down traversal uses this to merge information about
+/// predecessors to form the initial state for a new block.
+void BBState::MergePred(const BBState &Other) {
+ // Other.TopDownPathCount can be 0, in which case it is either dead or a
+ // loop backedge. Loop backedges are special.
+ TopDownPathCount += Other.TopDownPathCount;
+
+ // For each entry in the other set, if our set has an entry with the same key,
+ // merge the entries. Otherwise, copy the entry and merge it with an empty
+ // entry.
+ for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
+ ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
+ std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
+ Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
+ /*TopDown=*/true);
+ }
+
+ // For each entry in our set, if the other set doens't have an entry with the
+ // same key, force it to merge with an empty entry.
+ for (ptr_iterator MI = top_down_ptr_begin(),
+ ME = top_down_ptr_end(); MI != ME; ++MI)
+ if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
+ MI->second.Merge(PtrState(), /*TopDown=*/true);
+}
+
+/// MergeSucc - The bottom-up traversal uses this to merge information about
+/// successors to form the initial state for a new block.
+void BBState::MergeSucc(const BBState &Other) {
+ // Other.BottomUpPathCount can be 0, in which case it is either dead or a
+ // loop backedge. Loop backedges are special.
+ BottomUpPathCount += Other.BottomUpPathCount;
+
+ // For each entry in the other set, if our set has an entry with the
+ // same key, merge the entries. Otherwise, copy the entry and merge
+ // it with an empty entry.
+ for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
+ ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
+ std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
+ Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
+ /*TopDown=*/false);
+ }
+
+ // For each entry in our set, if the other set doens't have an entry
+ // with the same key, force it to merge with an empty entry.
+ for (ptr_iterator MI = bottom_up_ptr_begin(),
+ ME = bottom_up_ptr_end(); MI != ME; ++MI)
+ if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
+ MI->second.Merge(PtrState(), /*TopDown=*/false);
+}
+
+namespace {
+ /// ObjCARCOpt - The main ARC optimization pass.
+ class ObjCARCOpt : public FunctionPass {
+ bool Changed;
+ ProvenanceAnalysis PA;
+
+ /// RetainFunc, RelaseFunc - Declarations for objc_retain,
+ /// objc_retainBlock, and objc_release.
+ Function *RetainFunc, *RetainBlockFunc, *RetainRVFunc, *ReleaseFunc,
+ *AutoreleaseFunc;
+
+ /// RetainRVCallee, etc. - Declarations for ObjC runtime
+ /// functions, for use in creating calls to them. These are initialized
+ /// lazily to avoid cluttering up the Module with unused declarations.
+ Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee,
+ *RetainCallee, *AutoreleaseCallee;
+
+ /// UsedInThisFunciton - Flags which determine whether each of the
+ /// interesting runtine functions is in fact used in the current function.
+ unsigned UsedInThisFunction;
+
+ /// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release
+ /// metadata.
+ unsigned ImpreciseReleaseMDKind;
+
+ Constant *getRetainRVCallee(Module *M);
+ Constant *getAutoreleaseRVCallee(Module *M);
+ Constant *getReleaseCallee(Module *M);
+ Constant *getRetainCallee(Module *M);
+ Constant *getAutoreleaseCallee(Module *M);
+
+ void OptimizeRetainCall(Function &F, Instruction *Retain);
+ bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
+ void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV);
+ void OptimizeIndividualCalls(Function &F);
+
+ void CheckForCFGHazards(const BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ BBState &MyStates) const;
+ bool VisitBottomUp(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains);
+ bool VisitTopDown(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ DenseMap<Value *, RRInfo> &Releases);
+ bool Visit(Function &F,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases);
+
+ void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ SmallVectorImpl<Instruction *> &DeadInsts);
+
+ bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases);
+
+ void OptimizeWeakCalls(Function &F);
+
+ bool OptimizeSequences(Function &F);
+
+ void OptimizeReturns(Function &F);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+ virtual void releaseMemory();
+
+ public:
+ static char ID;
+ ObjCARCOpt() : FunctionPass(ID) {
+ initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCOpt::ID = 0;
+INITIALIZE_PASS_BEGIN(ObjCARCOpt,
+ "objc-arc", "ObjC ARC optimization", false, false)
+INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
+INITIALIZE_PASS_END(ObjCARCOpt,
+ "objc-arc", "ObjC ARC optimization", false, false)
+
+Pass *llvm::createObjCARCOptPass() {
+ return new ObjCARCOpt();
+}
+
+void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<ObjCARCAliasAnalysis>();
+ AU.addRequired<AliasAnalysis>();
+ // ARC optimization doesn't currently split critical edges.
+ AU.setPreservesCFG();
+}
+
+Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
+ if (!RetainRVCallee) {
+ LLVMContext &C = M->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ std::vector<const Type *> Params;
+ Params.push_back(I8X);
+ const FunctionType *FTy =
+ FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ RetainRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
+ Attributes);
+ }
+ return RetainRVCallee;
+}
+
+Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
+ if (!AutoreleaseRVCallee) {
+ LLVMContext &C = M->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ std::vector<const Type *> Params;
+ Params.push_back(I8X);
+ const FunctionType *FTy =
+ FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ AutoreleaseRVCallee =
+ M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
+ Attributes);
+ }
+ return AutoreleaseRVCallee;
+}
+
+Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
+ if (!ReleaseCallee) {
+ LLVMContext &C = M->getContext();
+ std::vector<const Type *> Params;
+ Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ ReleaseCallee =
+ M->getOrInsertFunction(
+ "objc_release",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attributes);
+ }
+ return ReleaseCallee;
+}
+
+Constant *ObjCARCOpt::getRetainCallee(Module *M) {
+ if (!RetainCallee) {
+ LLVMContext &C = M->getContext();
+ std::vector<const Type *> Params;
+ Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ RetainCallee =
+ M->getOrInsertFunction(
+ "objc_retain",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attributes);
+ }
+ return RetainCallee;
+}
+
+Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
+ if (!AutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ std::vector<const Type *> Params;
+ Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ AutoreleaseCallee =
+ M->getOrInsertFunction(
+ "objc_autorelease",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attributes);
+ }
+ return AutoreleaseCallee;
+}
+
+/// CanAlterRefCount - Test whether the given instruction can result in a
+/// reference count modification (positive or negative) for the pointer's
+/// object.
+static bool
+CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
+ ProvenanceAnalysis &PA, InstructionClass Class) {
+ switch (Class) {
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_User:
+ // These operations never directly modify a reference count.
+ return false;
+ default: break;
+ }
+
+ ImmutableCallSite CS = static_cast<const Value *>(Inst);
+ assert(CS && "Only calls can alter reference counts!");
+
+ // See if AliasAnalysis can help us with the call.
+ AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
+ if (AliasAnalysis::onlyReadsMemory(MRB))
+ return false;
+ if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I) {
+ const Value *Op = *I;
+ if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ }
+
+ // Assume the worst.
+ return true;
+}
+
+/// CanUse - Test whether the given instruction can "use" the given pointer's
+/// object in a way that requires the reference count to be positive.
+static bool
+CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
+ InstructionClass Class) {
+ // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
+ if (Class == IC_Call)
+ return false;
+
+ // Consider various instructions which may have pointer arguments which are
+ // not "uses".
+ if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
+ // Comparing a pointer with null, or any other constant, isn't really a use,
+ // because we don't care what the pointer points to, or about the values
+ // of any other dynamic reference-counted pointers.
+ if (!IsPotentialUse(ICI->getOperand(1)))
+ return false;
+ } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
+ // For calls, just check the arguments (and not the callee operand).
+ for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
+ OE = CS.arg_end(); OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // Special-case stores, because we don't care about the stored value, just
+ // the store address.
+ const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
+ // If we can't tell what the underlying object was, assume there is a
+ // dependence.
+ return IsPotentialUse(Op) && PA.related(Op, Ptr);
+ }
+
+ // Check each operand for a match.
+ for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
+ OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+}
+
+/// CanInterruptRV - Test whether the given instruction can autorelease
+/// any pointer or cause an autoreleasepool pop.
+static 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;
+ }
+}
+
+namespace {
+ /// DependenceKind - There are several kinds of dependence-like concepts in
+ /// use here.
+ enum DependenceKind {
+ NeedsPositiveRetainCount,
+ CanChangeRetainCount,
+ RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
+ RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
+ RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
+ };
+}
+
+/// Depends - Test if there can be dependencies on Inst through Arg. This
+/// function only tests dependencies relevant for removing pairs of calls.
+static bool
+Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
+ ProvenanceAnalysis &PA) {
+ // If we've reached the definition of Arg, stop.
+ if (Inst == Arg)
+ return true;
+
+ switch (Flavor) {
+ case NeedsPositiveRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanUse(Inst, Arg, PA, Class);
+ }
+ }
+
+ case CanChangeRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ // Conservatively assume this can decrement any count.
+ return true;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanAlterRefCount(Inst, Arg, PA, Class);
+ }
+ }
+
+ case RetainAutoreleaseDep:
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_AutoreleasepoolPop:
+ // Don't merge an objc_autorelease with an objc_retain inside a different
+ // autoreleasepool scope.
+ return true;
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Nothing else matters for objc_retainAutorelease formation.
+ return false;
+ }
+ break;
+
+ case RetainAutoreleaseRVDep: {
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Anything that can autorelease interrupts
+ // retainAutoreleaseReturnValue formation.
+ return CanInterruptRV(Class);
+ }
+ break;
+ }
+
+ case RetainRVDep:
+ return CanInterruptRV(GetBasicInstructionClass(Inst));
+ }
+
+ llvm_unreachable("Invalid dependence flavor");
+ return true;
+}
+
+/// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and
+/// find local and non-local dependencies on Arg.
+/// TODO: Cache results?
+static void
+FindDependencies(DependenceKind Flavor,
+ const Value *Arg,
+ BasicBlock *StartBB, Instruction *StartInst,
+ SmallPtrSet<Instruction *, 4> &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4> &Visited,
+ ProvenanceAnalysis &PA) {
+ BasicBlock::iterator StartPos = StartInst;
+
+ SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
+ Worklist.push_back(std::make_pair(StartBB, StartPos));
+ do {
+ std::pair<BasicBlock *, BasicBlock::iterator> Pair =
+ Worklist.pop_back_val();
+ BasicBlock *LocalStartBB = Pair.first;
+ BasicBlock::iterator LocalStartPos = Pair.second;
+ BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
+ for (;;) {
+ if (LocalStartPos == StartBBBegin) {
+ pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
+ if (PI == PE)
+ // If we've reached the function entry, produce a null dependence.
+ DependingInstructions.insert(0);
+ else
+ // Add the predecessors to the worklist.
+ do {
+ BasicBlock *PredBB = *PI;
+ if (Visited.insert(PredBB))
+ Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
+ } while (++PI != PE);
+ break;
+ }
+
+ Instruction *Inst = --LocalStartPos;
+ if (Depends(Flavor, Inst, Arg, PA)) {
+ DependingInstructions.insert(Inst);
+ break;
+ }
+ }
+ } while (!Worklist.empty());
+
+ // Determine whether the original StartBB post-dominates all of the blocks we
+ // visited. If not, insert a sentinal indicating that most optimizations are
+ // not safe.
+ for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
+ E = Visited.end(); I != E; ++I) {
+ const BasicBlock *BB = *I;
+ if (BB == StartBB)
+ continue;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
+ const BasicBlock *Succ = *SI;
+ if (Succ != StartBB && !Visited.count(Succ)) {
+ DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
+ return;
+ }
+ }
+ }
+}
+
+static bool isNullOrUndef(const Value *V) {
+ return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
+}
+
+static bool isNoopInstruction(const Instruction *I) {
+ return isa<BitCastInst>(I) ||
+ (isa<GetElementPtrInst>(I) &&
+ cast<GetElementPtrInst>(I)->hasAllZeroIndices());
+}
+
+/// OptimizeRetainCall - Turn objc_retain into
+/// objc_retainAutoreleasedReturnValue if the operand is a return value.
+void
+ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
+ CallSite CS(GetObjCArg(Retain));
+ Instruction *Call = CS.getInstruction();
+ if (!Call) return;
+ if (Call->getParent() != Retain->getParent()) return;
+
+ // Check that the call is next to the retain.
+ BasicBlock::iterator I = Call;
+ ++I;
+ while (isNoopInstruction(I)) ++I;
+ if (&*I != Retain)
+ return;
+
+ // Turn it to an objc_retainAutoreleasedReturnValue..
+ Changed = true;
+ ++NumPeeps;
+ cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
+}
+
+/// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into
+/// objc_retain if the operand is not a return value. Or, if it can be
+/// paired with an objc_autoreleaseReturnValue, delete the pair and
+/// return true.
+bool
+ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
+ // Check for the argument being from an immediately preceding call.
+ Value *Arg = GetObjCArg(RetainRV);
+ CallSite CS(Arg);
+ if (Instruction *Call = CS.getInstruction())
+ if (Call->getParent() == RetainRV->getParent()) {
+ BasicBlock::iterator I = Call;
+ ++I;
+ while (isNoopInstruction(I)) ++I;
+ if (&*I == RetainRV)
+ return false;
+ }
+
+ // Check for being preceded by an objc_autoreleaseReturnValue on the same
+ // pointer. In this case, we can delete the pair.
+ BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
+ if (I != Begin) {
+ do --I; while (I != Begin && isNoopInstruction(I));
+ if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
+ GetObjCArg(I) == Arg) {
+ Changed = true;
+ ++NumPeeps;
+ EraseInstruction(I);
+ EraseInstruction(RetainRV);
+ return true;
+ }
+ }
+
+ // Turn it to a plain objc_retain.
+ Changed = true;
+ ++NumPeeps;
+ cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
+ return false;
+}
+
+/// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into
+/// objc_autorelease if the result is not used as a return value.
+void
+ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) {
+ // Check for a return of the pointer value.
+ const Value *Ptr = GetObjCArg(AutoreleaseRV);
+ for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
+ UI != UE; ++UI) {
+ const User *I = *UI;
+ if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
+ return;
+ }
+
+ Changed = true;
+ ++NumPeeps;
+ cast<CallInst>(AutoreleaseRV)->
+ setCalledFunction(getAutoreleaseCallee(F.getParent()));
+}
+
+/// OptimizeIndividualCalls - Visit each call, one at a time, and make
+/// simplifications without doing any additional analysis.
+void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
+ // Reset all the flags in preparation for recomputing them.
+ UsedInThisFunction = 0;
+
+ // Visit all objc_* calls in F.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+
+ switch (Class) {
+ default: break;
+
+ // Delete no-op casts. These function calls have special semantics, but
+ // the semantics are entirely implemented via lowering in the front-end,
+ // so by the time they reach the optimizer, they are just no-op calls
+ // which return their argument.
+ //
+ // There are gray areas here, as the ability to cast reference-counted
+ // pointers to raw void* and back allows code to break ARC assumptions,
+ // however these are currently considered to be unimportant.
+ case IC_NoopCast:
+ Changed = true;
+ ++NumNoops;
+ EraseInstruction(Inst);
+ continue;
+
+ // If the pointer-to-weak-pointer is null, it's undefined behavior.
+ case IC_StoreWeak:
+ case IC_LoadWeak:
+ case IC_LoadWeakRetained:
+ case IC_InitWeak:
+ case IC_DestroyWeak: {
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(0))) {
+ const Type *Ty = CI->getArgOperand(0)->getType();
+ new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
+ Constant::getNullValue(Ty),
+ CI);
+ CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
+ CI->eraseFromParent();
+ continue;
+ }
+ break;
+ }
+ case IC_CopyWeak:
+ case IC_MoveWeak: {
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(0)) ||
+ isNullOrUndef(CI->getArgOperand(1))) {
+ const Type *Ty = CI->getArgOperand(0)->getType();
+ new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
+ Constant::getNullValue(Ty),
+ CI);
+ CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
+ CI->eraseFromParent();
+ continue;
+ }
+ break;
+ }
+ case IC_Retain:
+ OptimizeRetainCall(F, Inst);
+ break;
+ case IC_RetainRV:
+ if (OptimizeRetainRVCall(F, Inst))
+ continue;
+ break;
+ case IC_AutoreleaseRV:
+ OptimizeAutoreleaseRVCall(F, Inst);
+ break;
+ }
+
+ // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
+ if (IsAutorelease(Class) && Inst->use_empty()) {
+ CallInst *Call = cast<CallInst>(Inst);
+ const Value *Arg = Call->getArgOperand(0);
+ Arg = FindSingleUseIdentifiedObject(Arg);
+ if (Arg) {
+ Changed = true;
+ ++NumAutoreleases;
+
+ // Create the declaration lazily.
+ LLVMContext &C = Inst->getContext();
+ CallInst *NewCall =
+ CallInst::Create(getReleaseCallee(F.getParent()),
+ Call->getArgOperand(0), "", Call);
+ NewCall->setMetadata(ImpreciseReleaseMDKind,
+ MDNode::get(C, ArrayRef<Value *>()));
+ EraseInstruction(Call);
+ Inst = NewCall;
+ Class = IC_Release;
+ }
+ }
+
+ // For functions which can never be passed stack arguments, add
+ // a tail keyword.
+ if (IsAlwaysTail(Class)) {
+ Changed = true;
+ cast<CallInst>(Inst)->setTailCall();
+ }
+
+ // Set nounwind as needed.
+ if (IsNoThrow(Class)) {
+ Changed = true;
+ cast<CallInst>(Inst)->setDoesNotThrow();
+ }
+
+ if (!IsNoopOnNull(Class)) {
+ UsedInThisFunction |= 1 << Class;
+ continue;
+ }
+
+ const Value *Arg = GetObjCArg(Inst);
+
+ // ARC calls with null are no-ops. Delete them.
+ if (isNullOrUndef(Arg)) {
+ Changed = true;
+ ++NumNoops;
+ EraseInstruction(Inst);
+ continue;
+ }
+
+ // Keep track of which of retain, release, autorelease, and retain_block
+ // are actually present in this function.
+ UsedInThisFunction |= 1 << Class;
+
+ // If Arg is a PHI, and one or more incoming values to the
+ // PHI are null, and the call is control-equivalent to the PHI, and there
+ // are no relevant side effects between the PHI and the call, the call
+ // could be pushed up to just those paths with non-null incoming values.
+ // For now, don't bother splitting critical edges for this.
+ SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
+ Worklist.push_back(std::make_pair(Inst, Arg));
+ do {
+ std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
+ Inst = Pair.first;
+ Arg = Pair.second;
+
+ const PHINode *PN = dyn_cast<PHINode>(Arg);
+ if (!PN) continue;
+
+ // Determine if the PHI has any null operands, or any incoming
+ // critical edges.
+ bool HasNull = false;
+ bool HasCriticalEdges = false;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming =
+ StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
+ if (isNullOrUndef(Incoming))
+ HasNull = true;
+ else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
+ .getNumSuccessors() != 1) {
+ HasCriticalEdges = true;
+ break;
+ }
+ }
+ // If we have null operands and no critical edges, optimize.
+ if (!HasCriticalEdges && HasNull) {
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+
+ // Check that there is nothing that cares about the reference
+ // count between the call and the phi.
+ FindDependencies(NeedsPositiveRetainCount, Arg,
+ Inst->getParent(), Inst,
+ DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() == 1 &&
+ *DependingInstructions.begin() == PN) {
+ Changed = true;
+ ++NumPartialNoops;
+ // Clone the call into each predecessor that has a non-null value.
+ CallInst *CInst = cast<CallInst>(Inst);
+ const Type *ParamTy = CInst->getArgOperand(0)->getType();
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming =
+ StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
+ if (!isNullOrUndef(Incoming)) {
+ CallInst *Clone = cast<CallInst>(CInst->clone());
+ Value *Op = PN->getIncomingValue(i);
+ Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
+ if (Op->getType() != ParamTy)
+ Op = new BitCastInst(Op, ParamTy, "", InsertPos);
+ Clone->setArgOperand(0, Op);
+ Clone->insertBefore(InsertPos);
+ Worklist.push_back(std::make_pair(Clone, Incoming));
+ }
+ }
+ // Erase the original call.
+ EraseInstruction(CInst);
+ continue;
+ }
+ }
+ } while (!Worklist.empty());
+ }
+}
+
+/// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible
+/// control flow, or other CFG structures where moving code across the edge
+/// would result in it being executed more.
+void
+ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ BBState &MyStates) const {
+ // If any top-down local-use or possible-dec has a succ which is earlier in
+ // the sequence, forget it.
+ for (BBState::ptr_const_iterator I = MyStates.top_down_ptr_begin(),
+ E = MyStates.top_down_ptr_end(); I != E; ++I)
+ switch (I->second.GetSeq()) {
+ default: break;
+ case S_Use: {
+ const Value *Arg = I->first;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ bool SomeSuccHasSame = false;
+ bool AllSuccsHaveSame = true;
+ for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI)
+ switch (BBStates[*SI].getPtrBottomUpState(Arg).GetSeq()) {
+ case S_None:
+ case S_CanRelease:
+ MyStates.getPtrTopDownState(Arg).ClearSequenceProgress();
+ SomeSuccHasSame = false;
+ break;
+ case S_Use:
+ SomeSuccHasSame = true;
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ AllSuccsHaveSame = false;
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ // If the state at the other end of any of the successor edges
+ // matches the current state, require all edges to match. This
+ // guards against loops in the middle of a sequence.
+ if (SomeSuccHasSame && !AllSuccsHaveSame)
+ MyStates.getPtrTopDownState(Arg).ClearSequenceProgress();
+ }
+ case S_CanRelease: {
+ const Value *Arg = I->first;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ bool SomeSuccHasSame = false;
+ bool AllSuccsHaveSame = true;
+ for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI)
+ switch (BBStates[*SI].getPtrBottomUpState(Arg).GetSeq()) {
+ case S_None:
+ MyStates.getPtrTopDownState(Arg).ClearSequenceProgress();
+ SomeSuccHasSame = false;
+ break;
+ case S_CanRelease:
+ SomeSuccHasSame = true;
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Use:
+ AllSuccsHaveSame = false;
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ // If the state at the other end of any of the successor edges
+ // matches the current state, require all edges to match. This
+ // guards against loops in the middle of a sequence.
+ if (SomeSuccHasSame && !AllSuccsHaveSame)
+ MyStates.getPtrTopDownState(Arg).ClearSequenceProgress();
+ }
+ }
+}
+
+bool
+ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains) {
+ bool NestingDetected = false;
+ BBState &MyStates = BBStates[BB];
+
+ // Merge the states from each successor to compute the initial state
+ // for the current block.
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ succ_const_iterator SI(TI), SE(TI, false);
+ if (SI == SE)
+ MyStates.SetAsExit();
+ else
+ do {
+ const BasicBlock *Succ = *SI++;
+ if (Succ == BB)
+ continue;
+ DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
+ if (I == BBStates.end())
+ continue;
+ MyStates.InitFromSucc(I->second);
+ while (SI != SE) {
+ Succ = *SI++;
+ if (Succ != BB) {
+ I = BBStates.find(Succ);
+ if (I != BBStates.end())
+ MyStates.MergeSucc(I->second);
+ }
+ }
+ break;
+ } while (SI != SE);
+
+ // Visit all the instructions, bottom-up.
+ for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
+ Instruction *Inst = llvm::prior(I);
+ InstructionClass Class = GetInstructionClass(Inst);
+ const Value *Arg = 0;
+
+ switch (Class) {
+ case IC_Release: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrBottomUpState(Arg);
+
+ // If we see two releases in a row on the same pointer. If so, make
+ // a note, and we'll cicle back to revisit it after we've
+ // hopefully eliminated the second release, which may allow us to
+ // eliminate the first release too.
+ // Theoretically we could implement removal of nested retain+release
+ // pairs by making PtrState hold a stack of states, but this is
+ // simple and avoids adding overhead for the non-nested case.
+ if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease)
+ NestingDetected = true;
+
+ S.SetSeqToRelease(Inst->getMetadata(ImpreciseReleaseMDKind));
+ S.RRI.clear();
+ S.RRI.KnownIncremented = S.IsKnownIncremented();
+ S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
+ S.RRI.Calls.insert(Inst);
+
+ S.IncrementRefCount();
+ break;
+ }
+ case IC_RetainBlock:
+ case IC_Retain:
+ case IC_RetainRV: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrBottomUpState(Arg);
+ S.DecrementRefCount();
+
+ switch (S.GetSeq()) {
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Use:
+ S.RRI.ReverseInsertPts.clear();
+ // FALL THROUGH
+ case S_CanRelease:
+ // Don't do retain+release tracking for IC_RetainRV, because it's
+ // better to let it remain as the first instruction after a call.
+ if (Class != IC_RetainRV) {
+ S.RRI.IsRetainBlock = Class == IC_RetainBlock;
+ Retains[Inst] = S.RRI;
+ }
+ S.ClearSequenceProgress();
+ break;
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ break;
+ }
+ case IC_AutoreleasepoolPop:
+ // Conservatively, clear MyStates for all known pointers.
+ MyStates.clearBottomUpPointers();
+ continue;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ // These are irrelevant.
+ continue;
+ default:
+ break;
+ }
+
+ // Consider any other possible effects of this instruction on each
+ // pointer being tracked.
+ for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
+ ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
+ const Value *Ptr = MI->first;
+ if (Ptr == Arg)
+ continue; // Handled above.
+ PtrState &S = MI->second;
+ Sequence Seq = S.GetSeq();
+
+ // Check for possible retains and releases.
+ if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
+ // Check for a retain (we're going bottom-up here).
+ S.DecrementRefCount();
+
+ // Check for a release.
+ if (!IsRetain(Class) && Class != IC_RetainBlock)
+ switch (Seq) {
+ case S_Use:
+ S.SetSeq(S_CanRelease);
+ continue;
+ case S_CanRelease:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Stop:
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+
+ // Check for possible direct uses.
+ switch (Seq) {
+ case S_Release:
+ case S_MovableRelease:
+ if (CanUse(Inst, Ptr, PA, Class)) {
+ S.RRI.ReverseInsertPts.clear();
+ S.RRI.ReverseInsertPts.insert(Inst);
+ S.SetSeq(S_Use);
+ } else if (Seq == S_Release &&
+ (Class == IC_User || Class == IC_CallOrUser)) {
+ // Non-movable releases depend on any possible objc pointer use.
+ S.SetSeq(S_Stop);
+ S.RRI.ReverseInsertPts.clear();
+ S.RRI.ReverseInsertPts.insert(Inst);
+ }
+ break;
+ case S_Stop:
+ if (CanUse(Inst, Ptr, PA, Class))
+ S.SetSeq(S_Use);
+ break;
+ case S_CanRelease:
+ case S_Use:
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+ }
+
+ return NestingDetected;
+}
+
+bool
+ObjCARCOpt::VisitTopDown(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ DenseMap<Value *, RRInfo> &Releases) {
+ bool NestingDetected = false;
+ BBState &MyStates = BBStates[BB];
+
+ // Merge the states from each predecessor to compute the initial state
+ // for the current block.
+ const_pred_iterator PI(BB), PE(BB, false);
+ if (PI == PE)
+ MyStates.SetAsEntry();
+ else
+ do {
+ const BasicBlock *Pred = *PI++;
+ if (Pred == BB)
+ continue;
+ DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
+ if (I == BBStates.end())
+ continue;
+ MyStates.InitFromPred(I->second);
+ while (PI != PE) {
+ Pred = *PI++;
+ if (Pred != BB) {
+ I = BBStates.find(Pred);
+ if (I != BBStates.end())
+ MyStates.MergePred(I->second);
+ }
+ }
+ break;
+ } while (PI != PE);
+
+ // Visit all the instructions, top-down.
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ Instruction *Inst = I;
+ InstructionClass Class = GetInstructionClass(Inst);
+ const Value *Arg = 0;
+
+ switch (Class) {
+ case IC_RetainBlock:
+ case IC_Retain:
+ case IC_RetainRV: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrTopDownState(Arg);
+
+ // Don't do retain+release tracking for IC_RetainRV, because it's
+ // better to let it remain as the first instruction after a call.
+ if (Class != IC_RetainRV) {
+ // If we see two retains in a row on the same pointer. If so, make
+ // a note, and we'll cicle back to revisit it after we've
+ // hopefully eliminated the second retain, which may allow us to
+ // eliminate the first retain too.
+ // Theoretically we could implement removal of nested retain+release
+ // pairs by making PtrState hold a stack of states, but this is
+ // simple and avoids adding overhead for the non-nested case.
+ if (S.GetSeq() == S_Retain)
+ NestingDetected = true;
+
+ S.SetSeq(S_Retain);
+ S.RRI.clear();
+ S.RRI.IsRetainBlock = Class == IC_RetainBlock;
+ S.RRI.KnownIncremented = S.IsKnownIncremented();
+ S.RRI.Calls.insert(Inst);
+ }
+
+ S.IncrementRefCount();
+ break;
+ }
+ case IC_Release: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrTopDownState(Arg);
+ S.DecrementRefCount();
+
+ switch (S.GetSeq()) {
+ case S_Retain:
+ case S_CanRelease:
+ S.RRI.ReverseInsertPts.clear();
+ // FALL THROUGH
+ case S_Use:
+ S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
+ S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
+ Releases[Inst] = S.RRI;
+ S.ClearSequenceProgress();
+ break;
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ break;
+ }
+ case IC_AutoreleasepoolPop:
+ // Conservatively, clear MyStates for all known pointers.
+ MyStates.clearTopDownPointers();
+ continue;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ // These are irrelevant.
+ continue;
+ default:
+ break;
+ }
+
+ // Consider any other possible effects of this instruction on each
+ // pointer being tracked.
+ for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
+ ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
+ const Value *Ptr = MI->first;
+ if (Ptr == Arg)
+ continue; // Handled above.
+ PtrState &S = MI->second;
+ Sequence Seq = S.GetSeq();
+
+ // Check for possible releases.
+ if (!IsRetain(Class) && Class != IC_RetainBlock &&
+ CanAlterRefCount(Inst, Ptr, PA, Class)) {
+ // Check for a release.
+ S.DecrementRefCount();
+
+ // Check for a release.
+ switch (Seq) {
+ case S_Retain:
+ S.SetSeq(S_CanRelease);
+ S.RRI.ReverseInsertPts.clear();
+ S.RRI.ReverseInsertPts.insert(Inst);
+
+ // One call can't cause a transition from S_Retain to S_CanRelease
+ // and S_CanRelease to S_Use. If we've made the first transition,
+ // we're done.
+ continue;
+ case S_Use:
+ case S_CanRelease:
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ }
+
+ // Check for possible direct uses.
+ switch (Seq) {
+ case S_CanRelease:
+ if (CanUse(Inst, Ptr, PA, Class))
+ S.SetSeq(S_Use);
+ break;
+ case S_Use:
+ case S_Retain:
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ }
+ }
+
+ CheckForCFGHazards(BB, BBStates, MyStates);
+ return NestingDetected;
+}
+
+// Visit - Visit the function both top-down and bottom-up.
+bool
+ObjCARCOpt::Visit(Function &F,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases) {
+ // Use postorder for bottom-up, and reverse-postorder for top-down, because we
+ // magically know that loops will be well behaved, i.e. they won't repeatedly
+ // call retain on a single pointer without doing a release.
+ bool BottomUpNestingDetected = false;
+ SmallVector<BasicBlock *, 8> PostOrder;
+ for (po_iterator<Function *> I = po_begin(&F), E = po_end(&F); I != E; ++I) {
+ BasicBlock *BB = *I;
+ PostOrder.push_back(BB);
+
+ BottomUpNestingDetected |= VisitBottomUp(BB, BBStates, Retains);
+ }
+
+ // Iterate through the post-order in reverse order, achieving a
+ // reverse-postorder traversal. We don't use the ReversePostOrderTraversal
+ // class here because it works by computing its own full postorder iteration,
+ // recording the sequence, and playing it back in reverse. Since we're already
+ // doing a full iteration above, we can just record the sequence manually and
+ // avoid the cost of having ReversePostOrderTraversal compute it.
+ bool TopDownNestingDetected = false;
+ for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator
+ RI = PostOrder.rbegin(), RE = PostOrder.rend(); RI != RE; ++RI)
+ TopDownNestingDetected |= VisitTopDown(*RI, BBStates, Releases);
+
+ return TopDownNestingDetected && BottomUpNestingDetected;
+}
+
+/// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove.
+void ObjCARCOpt::MoveCalls(Value *Arg,
+ RRInfo &RetainsToMove,
+ RRInfo &ReleasesToMove,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ SmallVectorImpl<Instruction *> &DeadInsts) {
+ const Type *ArgTy = Arg->getType();
+ const Type *ParamTy =
+ (RetainRVFunc ? RetainRVFunc :
+ RetainFunc ? RetainFunc :
+ RetainBlockFunc)->arg_begin()->getType();
+
+ // Insert the new retain and release calls.
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ PI = ReleasesToMove.ReverseInsertPts.begin(),
+ PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
+ Instruction *InsertPt = *PI;
+ Value *MyArg = ArgTy == ParamTy ? Arg :
+ new BitCastInst(Arg, ParamTy, "", InsertPt);
+ CallInst *Call =
+ CallInst::Create(RetainsToMove.IsRetainBlock ?
+ RetainBlockFunc : RetainFunc,
+ MyArg, "", InsertPt);
+ Call->setDoesNotThrow();
+ if (!RetainsToMove.IsRetainBlock)
+ Call->setTailCall();
+ }
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ PI = RetainsToMove.ReverseInsertPts.begin(),
+ PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
+ Instruction *InsertPt = llvm::next(BasicBlock::iterator(*PI));
+ Value *MyArg = ArgTy == ParamTy ? Arg :
+ new BitCastInst(Arg, ParamTy, "", InsertPt);
+ CallInst *Call = CallInst::Create(ReleaseFunc, MyArg, "", InsertPt);
+ // Attach a clang.imprecise_release metadata tag, if appropriate.
+ if (MDNode *M = ReleasesToMove.ReleaseMetadata)
+ Call->setMetadata(ImpreciseReleaseMDKind, M);
+ Call->setDoesNotThrow();
+ if (ReleasesToMove.IsTailCallRelease)
+ Call->setTailCall();
+ }
+
+ // Delete the original retain and release calls.
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ AI = RetainsToMove.Calls.begin(),
+ AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
+ Instruction *OrigRetain = *AI;
+ Retains.blot(OrigRetain);
+ DeadInsts.push_back(OrigRetain);
+ }
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ AI = ReleasesToMove.Calls.begin(),
+ AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
+ Instruction *OrigRelease = *AI;
+ Releases.erase(OrigRelease);
+ DeadInsts.push_back(OrigRelease);
+ }
+}
+
+bool
+ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
+ &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases) {
+ bool AnyPairsCompletelyEliminated = false;
+ RRInfo RetainsToMove;
+ RRInfo ReleasesToMove;
+ SmallVector<Instruction *, 4> NewRetains;
+ SmallVector<Instruction *, 4> NewReleases;
+ SmallVector<Instruction *, 8> DeadInsts;
+
+ for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
+ E = Retains.end(); I != E; ) {
+ Value *V = (I++)->first;
+ if (!V) continue; // blotted
+
+ Instruction *Retain = cast<Instruction>(V);
+ Value *Arg = GetObjCArg(Retain);
+
+ // If the object being released is in static or stack storage, we know it's
+ // not being managed by ObjC reference counting, so we can delete pairs
+ // regardless of what possible decrements or uses lie between them.
+ bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
+
+ // If a pair happens in a region where it is known that the reference count
+ // is already incremented, we can similarly ignore possible decrements.
+ bool KnownIncrementedTD = true, KnownIncrementedBU = true;
+
+ // Connect the dots between the top-down-collected RetainsToMove and
+ // bottom-up-collected ReleasesToMove to form sets of related calls.
+ // This is an iterative process so that we connect multiple releases
+ // to multiple retains if needed.
+ unsigned OldDelta = 0;
+ unsigned NewDelta = 0;
+ unsigned OldCount = 0;
+ unsigned NewCount = 0;
+ bool FirstRelease = true;
+ bool FirstRetain = true;
+ NewRetains.push_back(Retain);
+ for (;;) {
+ for (SmallVectorImpl<Instruction *>::const_iterator
+ NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
+ Instruction *NewRetain = *NI;
+ MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
+ assert(It != Retains.end());
+ const RRInfo &NewRetainRRI = It->second;
+ KnownIncrementedTD &= NewRetainRRI.KnownIncremented;
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ LI = NewRetainRRI.Calls.begin(),
+ LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
+ Instruction *NewRetainRelease = *LI;
+ DenseMap<Value *, RRInfo>::const_iterator Jt =
+ Releases.find(NewRetainRelease);
+ if (Jt == Releases.end())
+ goto next_retain;
+ const RRInfo &NewRetainReleaseRRI = Jt->second;
+ assert(NewRetainReleaseRRI.Calls.count(NewRetain));
+ if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
+ OldDelta -=
+ BBStates[NewRetainRelease->getParent()].GetAllPathCount();
+
+ // Merge the ReleaseMetadata and IsTailCallRelease values.
+ if (FirstRelease) {
+ ReleasesToMove.ReleaseMetadata =
+ NewRetainReleaseRRI.ReleaseMetadata;
+ ReleasesToMove.IsTailCallRelease =
+ NewRetainReleaseRRI.IsTailCallRelease;
+ FirstRelease = false;
+ } else {
+ if (ReleasesToMove.ReleaseMetadata !=
+ NewRetainReleaseRRI.ReleaseMetadata)
+ ReleasesToMove.ReleaseMetadata = 0;
+ if (ReleasesToMove.IsTailCallRelease !=
+ NewRetainReleaseRRI.IsTailCallRelease)
+ ReleasesToMove.IsTailCallRelease = false;
+ }
+
+ // Collect the optimal insertion points.
+ if (!KnownSafe)
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
+ RE = NewRetainReleaseRRI.ReverseInsertPts.end();
+ RI != RE; ++RI) {
+ Instruction *RIP = *RI;
+ if (ReleasesToMove.ReverseInsertPts.insert(RIP))
+ NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
+ }
+ NewReleases.push_back(NewRetainRelease);
+ }
+ }
+ }
+ NewRetains.clear();
+ if (NewReleases.empty()) break;
+
+ // Back the other way.
+ for (SmallVectorImpl<Instruction *>::const_iterator
+ NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
+ Instruction *NewRelease = *NI;
+ DenseMap<Value *, RRInfo>::const_iterator It =
+ Releases.find(NewRelease);
+ assert(It != Releases.end());
+ const RRInfo &NewReleaseRRI = It->second;
+ KnownIncrementedBU &= NewReleaseRRI.KnownIncremented;
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ LI = NewReleaseRRI.Calls.begin(),
+ LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
+ Instruction *NewReleaseRetain = *LI;
+ MapVector<Value *, RRInfo>::const_iterator Jt =
+ Retains.find(NewReleaseRetain);
+ if (Jt == Retains.end())
+ goto next_retain;
+ const RRInfo &NewReleaseRetainRRI = Jt->second;
+ assert(NewReleaseRetainRRI.Calls.count(NewRelease));
+ if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
+ unsigned PathCount =
+ BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
+ OldDelta += PathCount;
+ OldCount += PathCount;
+
+ // Merge the IsRetainBlock values.
+ if (FirstRetain) {
+ RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
+ FirstRetain = false;
+ } else if (ReleasesToMove.IsRetainBlock !=
+ NewReleaseRetainRRI.IsRetainBlock)
+ // It's not possible to merge the sequences if one uses
+ // objc_retain and the other uses objc_retainBlock.
+ goto next_retain;
+
+ // Collect the optimal insertion points.
+ if (!KnownSafe)
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
+ RE = NewReleaseRetainRRI.ReverseInsertPts.end();
+ RI != RE; ++RI) {
+ Instruction *RIP = *RI;
+ if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
+ PathCount = BBStates[RIP->getParent()].GetAllPathCount();
+ NewDelta += PathCount;
+ NewCount += PathCount;
+ }
+ }
+ NewRetains.push_back(NewReleaseRetain);
+ }
+ }
+ }
+ NewReleases.clear();
+ if (NewRetains.empty()) break;
+ }
+
+ // If the pointer is known incremented, we can safely delete the pair
+ // regardless of what's between them.
+ if (KnownIncrementedTD || KnownIncrementedBU) {
+ RetainsToMove.ReverseInsertPts.clear();
+ ReleasesToMove.ReverseInsertPts.clear();
+ NewCount = 0;
+ }
+
+ // Determine whether the original call points are balanced in the retain and
+ // release calls through the program. If not, conservatively don't touch
+ // them.
+ // TODO: It's theoretically possible to do code motion in this case, as
+ // long as the existing imbalances are maintained.
+ if (OldDelta != 0)
+ goto next_retain;
+
+ // Determine whether the new insertion points we computed preserve the
+ // balance of retain and release calls through the program.
+ // TODO: If the fully aggressive solution isn't valid, try to find a
+ // less aggressive solution which is.
+ if (NewDelta != 0)
+ goto next_retain;
+
+ // Ok, everything checks out and we're all set. Let's move some code!
+ Changed = true;
+ AnyPairsCompletelyEliminated = NewCount == 0;
+ NumRRs += OldCount - NewCount;
+ MoveCalls(Arg, RetainsToMove, ReleasesToMove, Retains, Releases, DeadInsts);
+
+ next_retain:
+ NewReleases.clear();
+ NewRetains.clear();
+ RetainsToMove.clear();
+ ReleasesToMove.clear();
+ }
+
+ // Now that we're done moving everything, we can delete the newly dead
+ // instructions, as we no longer need them as insert points.
+ while (!DeadInsts.empty())
+ EraseInstruction(DeadInsts.pop_back_val());
+
+ return AnyPairsCompletelyEliminated;
+}
+
+/// OptimizeWeakCalls - Weak pointer optimizations.
+void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
+ // First, do memdep-style RLE and S2L optimizations. We can't use memdep
+ // itself because it uses AliasAnalysis and we need to do provenance
+ // queries instead.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
+ continue;
+
+ // Delete objc_loadWeak calls with no users.
+ if (Class == IC_LoadWeak && Inst->use_empty()) {
+ Inst->eraseFromParent();
+ continue;
+ }
+
+ // TODO: For now, just look for an earlier available version of this value
+ // within the same block. Theoretically, we could do memdep-style non-local
+ // analysis too, but that would want caching. A better approach would be to
+ // use the technique that EarlyCSE uses.
+ inst_iterator Current = llvm::prior(I);
+ BasicBlock *CurrentBB = Current.getBasicBlockIterator();
+ for (BasicBlock::iterator B = CurrentBB->begin(),
+ J = Current.getInstructionIterator();
+ J != B; --J) {
+ Instruction *EarlierInst = &*llvm::prior(J);
+ InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
+ switch (EarlierClass) {
+ case IC_LoadWeak:
+ case IC_LoadWeakRetained: {
+ // If this is loading from the same pointer, replace this load's value
+ // with that one.
+ CallInst *Call = cast<CallInst>(Inst);
+ CallInst *EarlierCall = cast<CallInst>(EarlierInst);
+ Value *Arg = Call->getArgOperand(0);
+ Value *EarlierArg = EarlierCall->getArgOperand(0);
+ switch (PA.getAA()->alias(Arg, EarlierArg)) {
+ case AliasAnalysis::MustAlias:
+ Changed = true;
+ // If the load has a builtin retain, insert a plain retain for it.
+ if (Class == IC_LoadWeakRetained) {
+ CallInst *CI =
+ CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
+ "", Call);
+ CI->setTailCall();
+ }
+ // Zap the fully redundant load.
+ Call->replaceAllUsesWith(EarlierCall);
+ Call->eraseFromParent();
+ goto clobbered;
+ case AliasAnalysis::MayAlias:
+ case AliasAnalysis::PartialAlias:
+ goto clobbered;
+ case AliasAnalysis::NoAlias:
+ break;
+ }
+ break;
+ }
+ case IC_StoreWeak:
+ case IC_InitWeak: {
+ // If this is storing to the same pointer and has the same size etc.
+ // replace this load's value with the stored value.
+ CallInst *Call = cast<CallInst>(Inst);
+ CallInst *EarlierCall = cast<CallInst>(EarlierInst);
+ Value *Arg = Call->getArgOperand(0);
+ Value *EarlierArg = EarlierCall->getArgOperand(0);
+ switch (PA.getAA()->alias(Arg, EarlierArg)) {
+ case AliasAnalysis::MustAlias:
+ Changed = true;
+ // If the load has a builtin retain, insert a plain retain for it.
+ if (Class == IC_LoadWeakRetained) {
+ CallInst *CI =
+ CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
+ "", Call);
+ CI->setTailCall();
+ }
+ // Zap the fully redundant load.
+ Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
+ Call->eraseFromParent();
+ goto clobbered;
+ case AliasAnalysis::MayAlias:
+ case AliasAnalysis::PartialAlias:
+ goto clobbered;
+ case AliasAnalysis::NoAlias:
+ break;
+ }
+ break;
+ }
+ case IC_MoveWeak:
+ case IC_CopyWeak:
+ // TOOD: Grab the copied value.
+ goto clobbered;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ case IC_User:
+ // Weak pointers are only modified through the weak entry points
+ // (and arbitrary calls, which could call the weak entry points).
+ break;
+ default:
+ // Anything else could modify the weak pointer.
+ goto clobbered;
+ }
+ }
+ clobbered:;
+ }
+
+ // Then, for each destroyWeak with an alloca operand, check to see if
+ // the alloca and all its users can be zapped.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ if (Class != IC_DestroyWeak)
+ continue;
+
+ CallInst *Call = cast<CallInst>(Inst);
+ Value *Arg = Call->getArgOperand(0);
+ if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
+ for (Value::use_iterator UI = Alloca->use_begin(),
+ UE = Alloca->use_end(); UI != UE; ++UI) {
+ Instruction *UserInst = cast<Instruction>(*UI);
+ switch (GetBasicInstructionClass(UserInst)) {
+ case IC_InitWeak:
+ case IC_StoreWeak:
+ case IC_DestroyWeak:
+ continue;
+ default:
+ goto done;
+ }
+ }
+ Changed = true;
+ for (Value::use_iterator UI = Alloca->use_begin(),
+ UE = Alloca->use_end(); UI != UE; ) {
+ CallInst *UserInst = cast<CallInst>(*UI++);
+ if (!UserInst->use_empty())
+ UserInst->replaceAllUsesWith(UserInst->getOperand(1));
+ UserInst->eraseFromParent();
+ }
+ Alloca->eraseFromParent();
+ done:;
+ }
+ }
+}
+
+/// OptimizeSequences - Identify program paths which execute sequences of
+/// retains and releases which can be eliminated.
+bool ObjCARCOpt::OptimizeSequences(Function &F) {
+ /// Releases, Retains - These are used to store the results of the main flow
+ /// analysis. These use Value* as the key instead of Instruction* so that the
+ /// map stays valid when we get around to rewriting code and calls get
+ /// replaced by arguments.
+ DenseMap<Value *, RRInfo> Releases;
+ MapVector<Value *, RRInfo> Retains;
+
+ /// BBStates, This is used during the traversal of the function to track the
+ /// states for each identified object at each block.
+ DenseMap<const BasicBlock *, BBState> BBStates;
+
+ // Analyze the CFG of the function, and all instructions.
+ bool NestingDetected = Visit(F, BBStates, Retains, Releases);
+
+ // Transform.
+ return PerformCodePlacement(BBStates, Retains, Releases) && NestingDetected;
+}
+
+/// OptimizeReturns - Look for this pattern:
+///
+/// %call = call i8* @something(...)
+/// %2 = call i8* @objc_retain(i8* %call)
+/// %3 = call i8* @objc_autorelease(i8* %2)
+/// ret i8* %3
+///
+/// And delete the retain and autorelease.
+///
+/// Otherwise if it's just this:
+///
+/// %3 = call i8* @objc_autorelease(i8* %2)
+/// ret i8* %3
+///
+/// convert the autorelease to autoreleaseRV.
+void ObjCARCOpt::OptimizeReturns(Function &F) {
+ if (!F.getReturnType()->isPointerTy())
+ return;
+
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+ for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
+ BasicBlock *BB = FI;
+ ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
+ if (!Ret) continue;
+
+ const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
+ FindDependencies(NeedsPositiveRetainCount, Arg,
+ BB, Ret, DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Autorelease =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+ if (!Autorelease)
+ goto next_block;
+ InstructionClass AutoreleaseClass =
+ GetBasicInstructionClass(Autorelease);
+ if (!IsAutorelease(AutoreleaseClass))
+ goto next_block;
+ if (GetObjCArg(Autorelease) != Arg)
+ goto next_block;
+
+ DependingInstructions.clear();
+ Visited.clear();
+
+ // Check that there is nothing that can affect the reference
+ // count between the autorelease and the retain.
+ FindDependencies(CanChangeRetainCount, Arg,
+ BB, Autorelease, DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Retain =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+
+ // Check that we found a retain with the same argument.
+ if (!Retain ||
+ !IsRetain(GetBasicInstructionClass(Retain)) ||
+ GetObjCArg(Retain) != Arg)
+ goto next_block;
+
+ DependingInstructions.clear();
+ Visited.clear();
+
+ // Convert the autorelease to an autoreleaseRV, since it's
+ // returning the value.
+ if (AutoreleaseClass == IC_Autorelease) {
+ Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
+ AutoreleaseClass = IC_AutoreleaseRV;
+ }
+
+ // Check that there is nothing that can affect the reference
+ // count between the retain and the call.
+ FindDependencies(CanChangeRetainCount, Arg, BB, Retain,
+ DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Call =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+
+ // Check that the pointer is the return value of the call.
+ if (!Call || Arg != Call)
+ goto next_block;
+
+ // Check that the call is a regular call.
+ InstructionClass Class = GetBasicInstructionClass(Call);
+ if (Class != IC_CallOrUser && Class != IC_Call)
+ goto next_block;
+
+ // If so, we can zap the retain and autorelease.
+ Changed = true;
+ ++NumRets;
+ EraseInstruction(Retain);
+ EraseInstruction(Autorelease);
+ }
+ }
+ }
+
+ next_block:
+ DependingInstructions.clear();
+ Visited.clear();
+ }
+}
+
+bool ObjCARCOpt::doInitialization(Module &M) {
+ if (!EnableARCOpts)
+ return false;
+
+ // Identify the imprecise release metadata kind.
+ ImpreciseReleaseMDKind =
+ M.getContext().getMDKindID("clang.imprecise_release");
+
+ // Identify the declarations for objc_retain and friends.
+ RetainFunc = M.getFunction("objc_retain");
+ RetainBlockFunc = M.getFunction("objc_retainBlock");
+ RetainRVFunc = M.getFunction("objc_retainAutoreleasedReturnValue");
+ ReleaseFunc = M.getFunction("objc_release");
+ AutoreleaseFunc = M.getFunction("objc_autorelease");
+
+ // Intuitively, objc_retain and others are nocapture, however in practice
+ // they are not, because they return their argument value. And objc_release
+ // calls finalizers.
+
+ // These are initialized lazily.
+ RetainRVCallee = 0;
+ AutoreleaseRVCallee = 0;
+ ReleaseCallee = 0;
+ RetainCallee = 0;
+ AutoreleaseCallee = 0;
+
+ return false;
+}
+
+bool ObjCARCOpt::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ Changed = false;
+
+ PA.setAA(&getAnalysis<AliasAnalysis>());
+
+ // This pass performs several distinct transformations. As a compile-time aid
+ // when compiling code that isn't ObjC, skip these if the relevant ObjC
+ // library functions aren't declared.
+
+ // Preliminary optimizations. This also computs UsedInThisFunction.
+ OptimizeIndividualCalls(F);
+
+ // Optimizations for weak pointers.
+ if (UsedInThisFunction & ((1 << IC_LoadWeak) |
+ (1 << IC_LoadWeakRetained) |
+ (1 << IC_StoreWeak) |
+ (1 << IC_InitWeak) |
+ (1 << IC_CopyWeak) |
+ (1 << IC_MoveWeak) |
+ (1 << IC_DestroyWeak)))
+ OptimizeWeakCalls(F);
+
+ // Optimizations for retain+release pairs.
+ if (UsedInThisFunction & ((1 << IC_Retain) |
+ (1 << IC_RetainRV) |
+ (1 << IC_RetainBlock)))
+ if (UsedInThisFunction & (1 << IC_Release))
+ // Run OptimizeSequences until it either stops making changes or
+ // no retain+release pair nesting is detected.
+ while (OptimizeSequences(F)) {}
+
+ // Optimizations if objc_autorelease is used.
+ if (UsedInThisFunction &
+ ((1 << IC_Autorelease) | (1 << IC_AutoreleaseRV)))
+ OptimizeReturns(F);
+
+ return Changed;
+}
+
+void ObjCARCOpt::releaseMemory() {
+ PA.clear();
+}
+
+//===----------------------------------------------------------------------===//
+// ARC contraction.
+//===----------------------------------------------------------------------===//
+
+// TODO: ObjCARCContract could insert PHI nodes when uses aren't
+// dominated by single calls.
+
+#include "llvm/Operator.h"
+#include "llvm/InlineAsm.h"
+#include "llvm/Analysis/Dominators.h"
+
+STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
+
+namespace {
+ /// ObjCARCContract - Late ARC optimizations. These change the IR in a way
+ /// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late.
+ class ObjCARCContract : public FunctionPass {
+ bool Changed;
+ AliasAnalysis *AA;
+ DominatorTree *DT;
+ ProvenanceAnalysis PA;
+
+ /// StoreStrongCallee, etc. - Declarations for ObjC runtime
+ /// functions, for use in creating calls to them. These are initialized
+ /// lazily to avoid cluttering up the Module with unused declarations.
+ Constant *StoreStrongCallee,
+ *RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee;
+
+ /// RetainRVMarker - The inline asm string to insert between calls and
+ /// RetainRV calls to make the optimization work on targets which need it.
+ const MDString *RetainRVMarker;
+
+ Constant *getStoreStrongCallee(Module *M);
+ Constant *getRetainAutoreleaseCallee(Module *M);
+ Constant *getRetainAutoreleaseRVCallee(Module *M);
+
+ bool ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited);
+
+ void ContractRelease(Instruction *Release,
+ inst_iterator &Iter);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+
+ public:
+ static char ID;
+ ObjCARCContract() : FunctionPass(ID) {
+ initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCContract::ID = 0;
+INITIALIZE_PASS_BEGIN(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_END(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+
+Pass *llvm::createObjCARCContractPass() {
+ return new ObjCARCContract();
+}
+
+void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<AliasAnalysis>();
+ AU.addRequired<DominatorTree>();
+ AU.setPreservesCFG();
+}
+
+Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
+ if (!StoreStrongCallee) {
+ LLVMContext &C = M->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ const Type *I8XX = PointerType::getUnqual(I8X);
+ std::vector<const Type *> Params;
+ Params.push_back(I8XX);
+ Params.push_back(I8X);
+
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ Attributes.addAttr(1, Attribute::NoCapture);
+
+ StoreStrongCallee =
+ M->getOrInsertFunction(
+ "objc_storeStrong",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attributes);
+ }
+ return StoreStrongCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
+ if (!RetainAutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ std::vector<const Type *> Params;
+ Params.push_back(I8X);
+ const FunctionType *FTy =
+ FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ RetainAutoreleaseCallee =
+ M->getOrInsertFunction("objc_retainAutorelease", FTy, Attributes);
+ }
+ return RetainAutoreleaseCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
+ if (!RetainAutoreleaseRVCallee) {
+ LLVMContext &C = M->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ std::vector<const Type *> Params;
+ Params.push_back(I8X);
+ const FunctionType *FTy =
+ FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttrListPtr Attributes;
+ Attributes.addAttr(~0u, Attribute::NoUnwind);
+ RetainAutoreleaseRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
+ Attributes);
+ }
+ return RetainAutoreleaseRVCallee;
+}
+
+/// ContractAutorelease - Merge an autorelease with a retain into a fused
+/// call.
+bool
+ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited) {
+ const Value *Arg = GetObjCArg(Autorelease);
+
+ // Check that there are no instructions between the retain and the autorelease
+ // (such as an autorelease_pop) which may change the count.
+ CallInst *Retain = 0;
+ if (Class == IC_AutoreleaseRV)
+ FindDependencies(RetainAutoreleaseRVDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+ else
+ FindDependencies(RetainAutoreleaseDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+
+ Visited.clear();
+ if (DependingInstructions.size() != 1) {
+ DependingInstructions.clear();
+ return false;
+ }
+
+ Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+ DependingInstructions.clear();
+
+ if (!Retain ||
+ GetBasicInstructionClass(Retain) != IC_Retain ||
+ GetObjCArg(Retain) != Arg)
+ return false;
+
+ Changed = true;
+ ++NumPeeps;
+
+ if (Class == IC_AutoreleaseRV)
+ Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
+ else
+ Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
+
+ EraseInstruction(Autorelease);
+ return true;
+}
+
+/// ContractRelease - Attempt to merge an objc_release with a store, load, and
+/// objc_retain to form an objc_storeStrong. This can be a little tricky because
+/// the instructions don't always appear in order, and there may be unrelated
+/// intervening instructions.
+void ObjCARCContract::ContractRelease(Instruction *Release,
+ inst_iterator &Iter) {
+ LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
+ if (!Load || Load->isVolatile()) return;
+
+ // For now, require everything to be in one basic block.
+ BasicBlock *BB = Release->getParent();
+ if (Load->getParent() != BB) return;
+
+ // Walk down to find the store.
+ BasicBlock::iterator I = Load, End = BB->end();
+ ++I;
+ AliasAnalysis::Location Loc = AA->getLocation(Load);
+ while (I != End &&
+ (&*I == Release ||
+ IsRetain(GetBasicInstructionClass(I)) ||
+ !(AA->getModRefInfo(I, Loc) & AliasAnalysis::Mod)))
+ ++I;
+ StoreInst *Store = dyn_cast<StoreInst>(I);
+ if (!Store || Store->isVolatile()) return;
+ if (Store->getPointerOperand() != Loc.Ptr) return;
+
+ Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
+
+ // Walk up to find the retain.
+ I = Store;
+ BasicBlock::iterator Begin = BB->begin();
+ while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
+ --I;
+ Instruction *Retain = I;
+ if (GetBasicInstructionClass(Retain) != IC_Retain) return;
+ if (GetObjCArg(Retain) != New) return;
+
+ Changed = true;
+ ++NumStoreStrongs;
+
+ LLVMContext &C = Release->getContext();
+ const Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ const Type *I8XX = PointerType::getUnqual(I8X);
+
+ Value *Args[] = { Load->getPointerOperand(), New };
+ if (Args[0]->getType() != I8XX)
+ Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
+ if (Args[1]->getType() != I8X)
+ Args[1] = new BitCastInst(Args[1], I8X, "", Store);
+ CallInst *StoreStrong =
+ CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
+ Args, array_endof(Args), "", Store);
+ StoreStrong->setDoesNotThrow();
+ StoreStrong->setDebugLoc(Store->getDebugLoc());
+
+ if (&*Iter == Store) ++Iter;
+ Store->eraseFromParent();
+ Release->eraseFromParent();
+ EraseInstruction(Retain);
+ if (Load->use_empty())
+ Load->eraseFromParent();
+}
+
+bool ObjCARCContract::doInitialization(Module &M) {
+ // These are initialized lazily.
+ StoreStrongCallee = 0;
+ RetainAutoreleaseCallee = 0;
+ RetainAutoreleaseRVCallee = 0;
+
+ // Initialize RetainRVMarker.
+ RetainRVMarker = 0;
+ if (NamedMDNode *NMD =
+ M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
+ if (NMD->getNumOperands() == 1) {
+ const MDNode *N = NMD->getOperand(0);
+ if (N->getNumOperands() == 1)
+ if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
+ RetainRVMarker = S;
+ }
+
+ return false;
+}
+
+bool ObjCARCContract::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ Changed = false;
+ AA = &getAnalysis<AliasAnalysis>();
+ DT = &getAnalysis<DominatorTree>();
+
+ PA.setAA(&getAnalysis<AliasAnalysis>());
+
+ // For ObjC library calls which return their argument, replace uses of the
+ // argument with uses of the call return value, if it dominates the use. This
+ // reduces register pressure.
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+
+ // Only these library routines return their argument. In particular,
+ // objc_retainBlock does not necessarily return its argument.
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ break;
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
+ continue;
+ break;
+ case IC_RetainRV: {
+ // If we're compiling for a target which needs a special inline-asm
+ // marker to do the retainAutoreleasedReturnValue optimization,
+ // insert it now.
+ if (!RetainRVMarker)
+ break;
+ BasicBlock::iterator BBI = Inst;
+ --BBI;
+ while (isNoopInstruction(BBI)) --BBI;
+ if (&*BBI == GetObjCArg(Inst)) {
+ InlineAsm *IA =
+ InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
+ /*isVarArg=*/false),
+ RetainRVMarker->getString(),
+ /*Constraints=*/"", /*hasSideEffects=*/true);
+ CallInst::Create(IA, "", Inst);
+ }
+ break;
+ }
+ case IC_InitWeak: {
+ // objc_initWeak(p, null) => *p = null
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(1))) {
+ Value *Null =
+ ConstantPointerNull::get(cast<PointerType>(CI->getType()));
+ Changed = true;
+ new StoreInst(Null, CI->getArgOperand(0), CI);
+ CI->replaceAllUsesWith(Null);
+ CI->eraseFromParent();
+ }
+ continue;
+ }
+ case IC_Release:
+ ContractRelease(Inst, I);
+ continue;
+ default:
+ continue;
+ }
+
+ // Don't use GetObjCArg because we don't want to look through bitcasts
+ // and such; to do the replacement, the argument must have type i8*.
+ const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
+ for (;;) {
+ // If we're compiling bugpointed code, don't get in trouble.
+ if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
+ break;
+ // Look through the uses of the pointer.
+ for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
+ UI != UE; ) {
+ Use &U = UI.getUse();
+ unsigned OperandNo = UI.getOperandNo();
+ ++UI; // Increment UI now, because we may unlink its element.
+ if (Instruction *UserInst = dyn_cast<Instruction>(U.getUser()))
+ if (Inst != UserInst && DT->dominates(Inst, UserInst)) {
+ Changed = true;
+ Instruction *Replacement = Inst;
+ const Type *UseTy = U.get()->getType();
+ if (PHINode *PHI = dyn_cast<PHINode>(UserInst)) {
+ // For PHI nodes, insert the bitcast in the predecessor block.
+ unsigned ValNo =
+ PHINode::getIncomingValueNumForOperand(OperandNo);
+ BasicBlock *BB =
+ PHI->getIncomingBlock(ValNo);
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "",
+ &BB->back());
+ for (unsigned i = 0, e = PHI->getNumIncomingValues();
+ i != e; ++i)
+ if (PHI->getIncomingBlock(i) == BB) {
+ // Keep the UI iterator valid.
+ if (&PHI->getOperandUse(
+ PHINode::getOperandNumForIncomingValue(i)) ==
+ &UI.getUse())
+ ++UI;
+ PHI->setIncomingValue(i, Replacement);
+ }
+ } else {
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "", UserInst);
+ U.set(Replacement);
+ }
+ }
+ }
+
+ // If Arg is a no-op casted pointer, strip one level of casts and
+ // iterate.
+ if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
+ Arg = BI->getOperand(0);
+ else if (isa<GEPOperator>(Arg) &&
+ cast<GEPOperator>(Arg)->hasAllZeroIndices())
+ Arg = cast<GEPOperator>(Arg)->getPointerOperand();
+ else if (isa<GlobalAlias>(Arg) &&
+ !cast<GlobalAlias>(Arg)->mayBeOverridden())
+ Arg = cast<GlobalAlias>(Arg)->getAliasee();
+ else
+ break;
+ }
+ }
+
+ return Changed;
+}
diff --git a/lib/Transforms/Scalar/Scalar.cpp b/lib/Transforms/Scalar/Scalar.cpp
index 32a0506..158d653 100644
--- a/lib/Transforms/Scalar/Scalar.cpp
+++ b/lib/Transforms/Scalar/Scalar.cpp
@@ -49,6 +49,10 @@
initializeLoopIdiomRecognizePass(Registry);
initializeLowerAtomicPass(Registry);
initializeMemCpyOptPass(Registry);
+ initializeObjCARCAliasAnalysisPass(Registry);
+ initializeObjCARCExpandPass(Registry);
+ initializeObjCARCContractPass(Registry);
+ initializeObjCARCOptPass(Registry);
initializeReassociatePass(Registry);
initializeRegToMemPass(Registry);
initializeSCCPPass(Registry);