///
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "objc-arc"
+#define DEBUG_TYPE "objc-arc-opts"
+#include "ObjCARC.h"
+#include "ObjCARCAliasAnalysis.h"
+#include "ProvenanceAnalysis.h"
+#include "DependencyAnalysis.h"
+
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-using namespace llvm;
+#include "llvm/Support/CFG.h"
-/// \brief A handy option to enable/disable all optimizations in this file.
-static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
+using namespace llvm;
+using namespace llvm::objcarc;
/// \defgroup MiscUtils Miscellaneous utilities that are not ARC specific.
/// @{
/// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
/// @{
-#include "llvm/ADT/StringSwitch.h"
-#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Transforms/Utils/Local.h"
-
-namespace {
- /// \enum InstructionClass
- /// \brief A simple classification for instructions.
- enum InstructionClass {
- IC_Retain, ///< objc_retain
- IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
- IC_RetainBlock, ///< objc_retainBlock
- IC_Release, ///< objc_release
- IC_Autorelease, ///< objc_autorelease
- IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
- IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
- IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
- IC_NoopCast, ///< objc_retainedObject, etc.
- IC_FusedRetainAutorelease, ///< objc_retainAutorelease
- IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
- IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
- IC_StoreWeak, ///< objc_storeWeak (primitive)
- IC_InitWeak, ///< objc_initWeak (derived)
- IC_LoadWeak, ///< objc_loadWeak (derived)
- IC_MoveWeak, ///< objc_moveWeak (derived)
- IC_CopyWeak, ///< objc_copyWeak (derived)
- IC_DestroyWeak, ///< objc_destroyWeak (derived)
- IC_StoreStrong, ///< objc_storeStrong (derived)
- IC_CallOrUser, ///< could call objc_release and/or "use" pointers
- IC_Call, ///< could call objc_release
- IC_User, ///< could "use" a pointer
- IC_None ///< anything else
- };
-
- raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class)
- LLVM_ATTRIBUTE_USED;
- raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class) {
- switch (Class) {
- case IC_Retain:
- return OS << "IC_Retain";
- case IC_RetainRV:
- return OS << "IC_RetainRV";
- case IC_RetainBlock:
- return OS << "IC_RetainBlock";
- case IC_Release:
- return OS << "IC_Release";
- case IC_Autorelease:
- return OS << "IC_Autorelease";
- case IC_AutoreleaseRV:
- return OS << "IC_AutoreleaseRV";
- case IC_AutoreleasepoolPush:
- return OS << "IC_AutoreleasepoolPush";
- case IC_AutoreleasepoolPop:
- return OS << "IC_AutoreleasepoolPop";
- case IC_NoopCast:
- return OS << "IC_NoopCast";
- case IC_FusedRetainAutorelease:
- return OS << "IC_FusedRetainAutorelease";
- case IC_FusedRetainAutoreleaseRV:
- return OS << "IC_FusedRetainAutoreleaseRV";
- case IC_LoadWeakRetained:
- return OS << "IC_LoadWeakRetained";
- case IC_StoreWeak:
- return OS << "IC_StoreWeak";
- case IC_InitWeak:
- return OS << "IC_InitWeak";
- case IC_LoadWeak:
- return OS << "IC_LoadWeak";
- case IC_MoveWeak:
- return OS << "IC_MoveWeak";
- case IC_CopyWeak:
- return OS << "IC_CopyWeak";
- case IC_DestroyWeak:
- return OS << "IC_DestroyWeak";
- case IC_StoreStrong:
- return OS << "IC_StoreStrong";
- case IC_CallOrUser:
- return OS << "IC_CallOrUser";
- case IC_Call:
- return OS << "IC_Call";
- case IC_User:
- return OS << "IC_User";
- case IC_None:
- return OS << "IC_None";
- }
- llvm_unreachable("Unknown instruction class!");
- }
-}
-
-/// \brief Test whether the given value is possible a retainable object pointer.
-static bool IsPotentialRetainableObjPtr(const Value *Op) {
- // Pointers to static or stack storage are not valid retainable object pointers.
- if (isa<Constant>(Op) || isa<AllocaInst>(Op))
- return false;
- // Special arguments can not be a valid retainable object pointer.
- if (const Argument *Arg = dyn_cast<Argument>(Op))
- if (Arg->hasByValAttr() ||
- Arg->hasNestAttr() ||
- Arg->hasStructRetAttr())
- return false;
- // Only consider values with pointer types.
- //
- // It seemes intuitive to exclude function pointer types as well, since
- // functions are never retainable object pointers, however clang occasionally
- // bitcasts retainable object pointers to function-pointer type temporarily.
- PointerType *Ty = dyn_cast<PointerType>(Op->getType());
- if (!Ty)
- return false;
- // Conservatively assume anything else is a potential retainable object pointer.
- return true;
-}
-
-/// \brief 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 (IsPotentialRetainableObjPtr(*I))
- return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
-
- return CS.onlyReadsMemory() ? IC_None : IC_Call;
-}
-
-/// \brief 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 (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
- 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 (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 (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
- if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
- if (Pte->getElementType()->isIntegerTy(8))
- if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
- 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)
- .Case("objc_storeStrong", IC_StoreStrong)
- .Default(IC_CallOrUser);
- // Second argument is i8**.
- if (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;
-}
-
-/// \brief 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 Intrinsic::returnaddress: case Intrinsic::frameaddress:
- case Intrinsic::stacksave: case Intrinsic::stackrestore:
- case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
- case Intrinsic::objectsize: case Intrinsic::prefetch:
- case Intrinsic::stackprotector:
- case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
- case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
- case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
- case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
- case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start: case Intrinsic::invariant_end:
- // 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:
- break;
- }
- }
- 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 (IsPotentialRetainableObjPtr(I->getOperand(1)))
- return IC_User;
- break;
- default:
- // For anything else, check all the operands.
- // Note that this includes both operands of a Store: while the first
- // operand isn't actually being dereferenced, it is being stored to
- // memory where we can no longer track who might read it and dereference
- // it, so we have to consider it potentially used.
- for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
- OI != OE; ++OI)
- if (IsPotentialRetainableObjPtr(*OI))
- return IC_User;
- }
- }
-
- // Otherwise, it's totally inert for ARC purposes.
- return IC_None;
-}
-
-/// \brief Determine which objc runtime call instruction class V belongs to.
-///
-/// This is similar to GetInstructionClass except that it only detects objc
-/// runtime calls. This allows it to be faster.
-///
-static InstructionClass GetBasicInstructionClass(const Value *V) {
- if (const CallInst *CI = dyn_cast<CallInst>(V)) {
- if (const Function *F = CI->getCalledFunction())
- return GetFunctionClass(F);
- // Otherwise, be conservative.
- return IC_CallOrUser;
- }
-
- // Otherwise, be conservative.
- return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
-}
-
-/// \brief Test if the given class is objc_retain or equivalent.
-static bool IsRetain(InstructionClass Class) {
- return Class == IC_Retain ||
- Class == IC_RetainRV;
-}
-
-/// \brief Test if the given class is objc_autorelease or equivalent.
-static bool IsAutorelease(InstructionClass Class) {
- return Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV;
-}
-
-/// \brief Test if the given class represents instructions which return their
-/// argument verbatim.
-static bool IsForwarding(InstructionClass Class) {
- // objc_retainBlock technically doesn't always return its argument
- // verbatim, but it doesn't matter for our purposes here.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_RetainBlock ||
- Class == IC_NoopCast;
-}
-
-/// \brief Test if the given class represents instructions which do nothing if
-/// passed a null pointer.
-static bool IsNoopOnNull(InstructionClass Class) {
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Release ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_RetainBlock;
-}
-
-/// \brief Test if the given class represents instructions which are always safe
-/// to mark with the "tail" keyword.
-static bool IsAlwaysTail(InstructionClass Class) {
- // IC_RetainBlock may be given a stack argument.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_AutoreleaseRV;
-}
-
-/// \brief Test if the given class represents instructions which are never safe
-/// to mark with the "tail" keyword.
-static bool IsNeverTail(InstructionClass Class) {
- /// It is never safe to tail call objc_autorelease since by tail calling
- /// objc_autorelease, we also tail call -[NSObject autorelease] which supports
- /// fast autoreleasing causing our object to be potentially reclaimed from the
- /// autorelease pool which violates the semantics of __autoreleasing types in
- /// ARC.
- return Class == IC_Autorelease;
-}
-
-/// \brief Test if the given class represents instructions which are always safe
-/// to mark with the nounwind attribute.
-static bool IsNoThrow(InstructionClass Class) {
- // objc_retainBlock is not nounwind because it calls user copy constructors
- // which could theoretically throw.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Release ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_AutoreleasepoolPush ||
- Class == IC_AutoreleasepoolPop;
-}
-
-/// \brief Erase the given instruction.
-///
-/// Many ObjC calls return their argument verbatim,
-/// so if it's such a call and the return value has users, replace them with the
-/// argument value.
-///
-static void EraseInstruction(Instruction *CI) {
- Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
-
- bool Unused = CI->use_empty();
-
- if (!Unused) {
- // Replace the return value with the argument.
- assert(IsForwarding(GetBasicInstructionClass(CI)) &&
- "Can't delete non-forwarding instruction with users!");
- CI->replaceAllUsesWith(OldArg);
- }
-
- CI->eraseFromParent();
-
- if (Unused)
- RecursivelyDeleteTriviallyDeadInstructions(OldArg);
-}
-
-/// \brief 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;
-}
-
-/// \brief This is a wrapper around Value::stripPointerCasts which also knows
-/// how to look through objc_retain and objc_autorelease calls, which we know to
-/// return their argument verbatim.
-static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
- for (;;) {
- V = V->stripPointerCasts();
- if (!IsForwarding(GetBasicInstructionClass(V)))
- break;
- V = cast<CallInst>(V)->getArgOperand(0);
- }
- return V;
-}
-
-/// \brief This is a wrapper around Value::stripPointerCasts which also knows
-/// how to look through objc_retain and objc_autorelease calls, which we know to
-/// return their argument verbatim.
-static Value *StripPointerCastsAndObjCCalls(Value *V) {
- for (;;) {
- V = V->stripPointerCasts();
- if (!IsForwarding(GetBasicInstructionClass(V)))
- break;
- V = cast<CallInst>(V)->getArgOperand(0);
- }
- return V;
-}
-
-/// \brief Assuming the given instruction is one of the special calls such as
-/// objc_retain or objc_release, return the argument value, stripped of no-op
-/// casts and forwarding calls.
-static Value *GetObjCArg(Value *Inst) {
- return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
-}
-
-/// \brief Return true if this value refers to a distinct and identifiable
-/// object.
-///
-/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
-/// special knowledge of ObjC conventions.
-static bool IsObjCIdentifiedObject(const Value *V) {
- // Assume that call results and arguments have their own "provenance".
- // Constants (including GlobalVariables) and Allocas are never
- // reference-counted.
- if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
- isa<Argument>(V) || isa<Constant>(V) ||
- isa<AllocaInst>(V))
- return true;
-
- if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
- const Value *Pointer =
- StripPointerCastsAndObjCCalls(LI->getPointerOperand());
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
- // A constant pointer can't be pointing to an object on the heap. It may
- // be reference-counted, but it won't be deleted.
- if (GV->isConstant())
- return true;
- StringRef Name = GV->getName();
- // These special variables are known to hold values which are not
- // reference-counted pointers.
- if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
- Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
- Name.startswith("\01l_objc_msgSend_fixup_"))
- return true;
- }
- }
-
- return false;
-}
-
/// \brief 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) {
return 0;
}
-/// \brief Test if the given module looks interesting to run ARC optimization
-/// on.
-static bool ModuleHasARC(const Module &M) {
- return
- M.getNamedValue("objc_retain") ||
- M.getNamedValue("objc_release") ||
- M.getNamedValue("objc_autorelease") ||
- M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
- M.getNamedValue("objc_retainBlock") ||
- M.getNamedValue("objc_autoreleaseReturnValue") ||
- M.getNamedValue("objc_autoreleasePoolPush") ||
- M.getNamedValue("objc_loadWeakRetained") ||
- M.getNamedValue("objc_loadWeak") ||
- M.getNamedValue("objc_destroyWeak") ||
- M.getNamedValue("objc_storeWeak") ||
- M.getNamedValue("objc_initWeak") ||
- M.getNamedValue("objc_moveWeak") ||
- M.getNamedValue("objc_copyWeak") ||
- M.getNamedValue("objc_retainedObject") ||
- M.getNamedValue("objc_unretainedObject") ||
- M.getNamedValue("objc_unretainedPointer");
-}
-
/// \brief Test whether the given pointer, which is an Objective C block
/// pointer, does not "escape".
///
return false;
}
-/// @}
-///
-/// \defgroup ARCAA Extends alias analysis using ObjC specific knowledge.
-/// @{
-
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/Passes.h"
-#include "llvm/Pass.h"
-
-namespace {
- /// \brief 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);
- }
-
- /// 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 static_cast<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_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.
- // Note that this doesn't include objc_retainBlock, because it updates
- // pointers when it copies block data.
- 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);
-}
-
-/// @}
-///
-/// \defgroup ARCExpansion Early ARC Optimizations.
-/// @{
-
-#include "llvm/Support/InstIterator.h"
-#include "llvm/Transforms/ObjCARC.h"
-
-namespace {
- /// \brief Early ARC transformations.
- class ObjCARCExpand : public FunctionPass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- 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::doInitialization(Module &M) {
- Run = ModuleHasARC(M);
- return false;
-}
-
-bool ObjCARCExpand::runOnFunction(Function &F) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- bool Changed = false;
-
- DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName() << "\n");
-
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
- Instruction *Inst = &*I;
-
- DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << *Inst << "\n");
-
- 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 the contract pass.
- Changed = true;
- Value *Value = cast<CallInst>(Inst)->getArgOperand(0);
- DEBUG(dbgs() << "ObjCARCExpand: Old = " << *Inst << "\n"
- " New = " << *Value << "\n");
- Inst->replaceAllUsesWith(Value);
- break;
- }
- default:
- break;
- }
- }
-
- DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n");
-
- return Changed;
-}
-
-/// @}
-///
-/// \defgroup ARCAPElim ARC Autorelease Pool Elimination.
-/// @{
-
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/IR/Constants.h"
-
-namespace {
- /// \brief Autorelease pool elimination.
- class ObjCARCAPElim : public ModulePass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool runOnModule(Module &M);
-
- static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0);
- static bool OptimizeBB(BasicBlock *BB);
-
- public:
- static char ID;
- ObjCARCAPElim() : ModulePass(ID) {
- initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCAPElim::ID = 0;
-INITIALIZE_PASS(ObjCARCAPElim,
- "objc-arc-apelim",
- "ObjC ARC autorelease pool elimination",
- false, false)
-
-Pass *llvm::createObjCARCAPElimPass() {
- return new ObjCARCAPElim();
-}
-
-void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
-}
-
-/// Interprocedurally determine if calls made by the given call site can
-/// possibly produce autoreleases.
-bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) {
- if (const Function *Callee = CS.getCalledFunction()) {
- if (Callee->isDeclaration() || Callee->mayBeOverridden())
- return true;
- for (Function::const_iterator I = Callee->begin(), E = Callee->end();
- I != E; ++I) {
- const BasicBlock *BB = I;
- for (BasicBlock::const_iterator J = BB->begin(), F = BB->end();
- J != F; ++J)
- if (ImmutableCallSite JCS = ImmutableCallSite(J))
- // This recursion depth limit is arbitrary. It's just great
- // enough to cover known interesting testcases.
- if (Depth < 3 &&
- !JCS.onlyReadsMemory() &&
- MayAutorelease(JCS, Depth + 1))
- return true;
- }
- return false;
- }
-
- return true;
-}
-
-bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) {
- bool Changed = false;
-
- Instruction *Push = 0;
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
- Instruction *Inst = I++;
- switch (GetBasicInstructionClass(Inst)) {
- case IC_AutoreleasepoolPush:
- Push = Inst;
- break;
- case IC_AutoreleasepoolPop:
- // If this pop matches a push and nothing in between can autorelease,
- // zap the pair.
- if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) {
- Changed = true;
- DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop "
- "autorelease pair:\n"
- " Pop: " << *Inst << "\n"
- << " Push: " << *Push << "\n");
- Inst->eraseFromParent();
- Push->eraseFromParent();
- }
- Push = 0;
- break;
- case IC_CallOrUser:
- if (MayAutorelease(ImmutableCallSite(Inst)))
- Push = 0;
- break;
- default:
- break;
- }
- }
-
- return Changed;
-}
-
-bool ObjCARCAPElim::runOnModule(Module &M) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!ModuleHasARC(M))
- return false;
-
- // Find the llvm.global_ctors variable, as the first step in
- // identifying the global constructors. In theory, unnecessary autorelease
- // pools could occur anywhere, but in practice it's pretty rare. Global
- // ctors are a place where autorelease pools get inserted automatically,
- // so it's pretty common for them to be unnecessary, and it's pretty
- // profitable to eliminate them.
- GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
- if (!GV)
- return false;
-
- assert(GV->hasDefinitiveInitializer() &&
- "llvm.global_ctors is uncooperative!");
-
- bool Changed = false;
-
- // Dig the constructor functions out of GV's initializer.
- ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
- for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
- OI != OE; ++OI) {
- Value *Op = *OI;
- // llvm.global_ctors is an array of pairs where the second members
- // are constructor functions.
- Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
- // If the user used a constructor function with the wrong signature and
- // it got bitcasted or whatever, look the other way.
- if (!F)
- continue;
- // Only look at function definitions.
- if (F->isDeclaration())
- continue;
- // Only look at functions with one basic block.
- if (llvm::next(F->begin()) != F->end())
- continue;
- // Ok, a single-block constructor function definition. Try to optimize it.
- Changed |= OptimizeBB(F->begin());
- }
-
- return Changed;
-}
-
/// @}
///
/// \defgroup ARCOpt ARC Optimization.
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/LLVMContext.h"
-#include "llvm/Support/CFG.h"
STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
STATISTIC(NumRRs, "Number of retain+release paths eliminated");
STATISTIC(NumPeeps, "Number of calls peephole-optimized");
-namespace {
- /// \brief This is similar to BasicAliasAnalysis, and it uses many of the same
- /// techniques, except it uses special ObjC-specific reasoning about pointer
- /// relationships.
- ///
- /// In this context ``Provenance'' is defined as the history of an object's
- /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
- /// an ``independent provenance source'' of a pointer to determine whether or
- /// not two pointers have the same provenance source and thus could
- /// potentially be related.
- 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);
-
- void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
- ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
-
- 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())
- return related(A->getTrueValue(), SB->getTrueValue()) ||
- related(A->getFalseValue(), SB->getFalseValue());
-
- // Check both arms of the Select node individually.
- return related(A->getTrueValue(), B) ||
- related(A->getFalseValue(), B);
-}
-
-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;
-}
-
-/// 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) {
- // Check for an obvious escape.
- if (isa<LoadInst>(B))
- return isStoredObjCPointer(A);
- if (BIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(A))
- return isStoredObjCPointer(B);
- // Both pointers are identified and escapes aren't an evident problem.
- return false;
- }
- } else if (BIsIdentified) {
- // Check for an obvious escape.
- if (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 {
/// \enum Sequence
///
Attribute);
}
return AutoreleaseRVCallee;
-}
-
-Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
- if (!ReleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- ReleaseCallee =
- M->getOrInsertFunction(
- "objc_release",
- FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
- Attribute);
- }
- return ReleaseCallee;
-}
-
-Constant *ObjCARCOpt::getRetainCallee(Module *M) {
- if (!RetainCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainCallee =
- M->getOrInsertFunction(
- "objc_retain",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- Attribute);
- }
- return RetainCallee;
-}
-
-Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
- if (!RetainBlockCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- // objc_retainBlock is not nounwind because it calls user copy constructors
- // which could theoretically throw.
- RetainBlockCallee =
- M->getOrInsertFunction(
- "objc_retainBlock",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- AttributeSet());
- }
- return RetainBlockCallee;
-}
-
-Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
- if (!AutoreleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- AutoreleaseCallee =
- M->getOrInsertFunction(
- "objc_autorelease",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- Attribute);
- }
- return AutoreleaseCallee;
-}
-
-/// Test whether the given value is possible a reference-counted pointer,
-/// including tests which utilize AliasAnalysis.
-static bool IsPotentialRetainableObjPtr(const Value *Op, AliasAnalysis &AA) {
- // First make the rudimentary check.
- if (!IsPotentialRetainableObjPtr(Op))
- return false;
-
- // Objects in constant memory are not reference-counted.
- if (AA.pointsToConstantMemory(Op))
- return false;
-
- // Pointers in constant memory are not pointing to reference-counted objects.
- if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
- if (AA.pointsToConstantMemory(LI->getPointerOperand()))
- return false;
-
- // Otherwise assume the worst.
- return true;
-}
-
-/// 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 (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
- }
-
- // Assume the worst.
- return true;
-}
-
-/// 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 (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
- 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 (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && 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 IsPotentialRetainableObjPtr(Op, *PA.getAA()) && 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 (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
-}
-
-/// 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 {
- /// \enum DependenceKind
- /// \brief Defines different dependence kinds among various ARC constructs.
- ///
- /// There are several kinds of dependence-like concepts in use here.
- ///
- enum DependenceKind {
- NeedsPositiveRetainCount,
- AutoreleasePoolBoundary,
- CanChangeRetainCount,
- RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
- RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
- RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
- };
-}
-
-/// 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 AutoreleasePoolBoundary: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- // These mark the end and begin of an autorelease pool scope.
- return true;
- default:
- // Nothing else does this.
- return false;
- }
- }
-
- 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:
- case IC_AutoreleasepoolPush:
- // 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;
- }
-
- 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);
- }
- }
+}
- case RetainRVDep:
- return CanInterruptRV(GetBasicInstructionClass(Inst));
+Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
+ if (!ReleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ ReleaseCallee =
+ M->getOrInsertFunction(
+ "objc_release",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attribute);
}
-
- llvm_unreachable("Invalid dependence flavor");
+ return ReleaseCallee;
}
-/// 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;
- }
- }
+Constant *ObjCARCOpt::getRetainCallee(Module *M) {
+ if (!RetainCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainCallee =
+ M->getOrInsertFunction(
+ "objc_retain",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attribute);
}
+ return RetainCallee;
}
-static bool isNullOrUndef(const Value *V) {
- return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
+Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
+ if (!RetainBlockCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ // objc_retainBlock is not nounwind because it calls user copy constructors
+ // which could theoretically throw.
+ RetainBlockCallee =
+ M->getOrInsertFunction(
+ "objc_retainBlock",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ AttributeSet());
+ }
+ return RetainBlockCallee;
}
-static bool isNoopInstruction(const Instruction *I) {
- return isa<BitCastInst>(I) ||
- (isa<GetElementPtrInst>(I) &&
- cast<GetElementPtrInst>(I)->hasAllZeroIndices());
+Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
+ if (!AutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ AutoreleaseCallee =
+ M->getOrInsertFunction(
+ "objc_autorelease",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attribute);
+ }
+ return AutoreleaseCallee;
}
/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
/// @}
///
-/// \defgroup ARCContract ARC Contraction.
-/// @{
-
-// TODO: ObjCARCContract could insert PHI nodes when uses aren't
-// dominated by single calls.
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/IR/InlineAsm.h"
-#include "llvm/IR/Operator.h"
-
-STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
-
-namespace {
- /// \brief 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;
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- /// 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.
-
- /// Declaration for objc_storeStrong().
- Constant *StoreStrongCallee;
- /// Declaration for objc_retainAutorelease().
- Constant *RetainAutoreleaseCallee;
- /// Declaration for objc_retainAutoreleaseReturnValue().
- Constant *RetainAutoreleaseRVCallee;
-
- /// The inline asm string to insert between calls and RetainRV calls to make
- /// the optimization work on targets which need it.
- const MDString *RetainRVMarker;
-
- /// The set of inserted objc_storeStrong calls. If at the end of walking the
- /// function we have found no alloca instructions, these calls can be marked
- /// "tail".
- SmallPtrSet<CallInst *, 8> StoreStrongCalls;
-
- 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();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *I8XX = PointerType::getUnqual(I8X);
- Type *Params[] = { I8XX, I8X };
-
- AttributeSet Attr = AttributeSet()
- .addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind)
- .addAttribute(M->getContext(), 1, Attribute::NoCapture);
-
- StoreStrongCallee =
- M->getOrInsertFunction(
- "objc_storeStrong",
- FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
- Attr);
- }
- return StoreStrongCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
- if (!RetainAutoreleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseCallee =
- M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
- }
- return RetainAutoreleaseCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
- if (!RetainAutoreleaseRVCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseRVCallee =
- M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
- Attribute);
- }
- return RetainAutoreleaseRVCallee;
-}
-
-/// 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;
-
- DEBUG(dbgs() << "ObjCARCContract::ContractAutorelease: Fusing "
- "retain/autorelease. Erasing: " << *Autorelease << "\n"
- " Old Retain: "
- << *Retain << "\n");
-
- if (Class == IC_AutoreleaseRV)
- Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
- else
- Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
-
- DEBUG(dbgs() << " New Retain: "
- << *Retain << "\n");
-
- EraseInstruction(Autorelease);
- return true;
-}
-
-/// 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->isSimple()) 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 and the release, which may be in either order.
- BasicBlock::iterator I = Load, End = BB->end();
- ++I;
- AliasAnalysis::Location Loc = AA->getLocation(Load);
- StoreInst *Store = 0;
- bool SawRelease = false;
- for (; !Store || !SawRelease; ++I) {
- if (I == End)
- return;
-
- Instruction *Inst = I;
- if (Inst == Release) {
- SawRelease = true;
- continue;
- }
-
- InstructionClass Class = GetBasicInstructionClass(Inst);
-
- // Unrelated retains are harmless.
- if (IsRetain(Class))
- continue;
-
- if (Store) {
- // The store is the point where we're going to put the objc_storeStrong,
- // so make sure there are no uses after it.
- if (CanUse(Inst, Load, PA, Class))
- return;
- } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
- // We are moving the load down to the store, so check for anything
- // else which writes to the memory between the load and the store.
- Store = dyn_cast<StoreInst>(Inst);
- if (!Store || !Store->isSimple()) 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();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- 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, "", Store);
- StoreStrong->setDoesNotThrow();
- StoreStrong->setDebugLoc(Store->getDebugLoc());
-
- // We can't set the tail flag yet, because we haven't yet determined
- // whether there are any escaping allocas. Remember this call, so that
- // we can set the tail flag once we know it's safe.
- StoreStrongCalls.insert(StoreStrong);
-
- if (&*Iter == Store) ++Iter;
- Store->eraseFromParent();
- Release->eraseFromParent();
- EraseInstruction(Retain);
- if (Load->use_empty())
- Load->eraseFromParent();
-}
-
-bool ObjCARCContract::doInitialization(Module &M) {
- // If nothing in the Module uses ARC, don't do anything.
- Run = ModuleHasARC(M);
- if (!Run)
- return false;
-
- // 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;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- Changed = false;
- AA = &getAnalysis<AliasAnalysis>();
- DT = &getAnalysis<DominatorTree>();
-
- PA.setAA(&getAnalysis<AliasAnalysis>());
-
- // Track whether it's ok to mark objc_storeStrong calls with the "tail"
- // keyword. Be conservative if the function has variadic arguments.
- // It seems that functions which "return twice" are also unsafe for the
- // "tail" argument, because they are setjmp, which could need to
- // return to an earlier stack state.
- bool TailOkForStoreStrongs = !F.isVarArg() &&
- !F.callsFunctionThatReturnsTwice();
-
- // 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++;
-
- DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
-
- // 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;
- BasicBlock *InstParent = Inst->getParent();
-
- // Step up to see if the call immediately precedes the RetainRV call.
- // If it's an invoke, we have to cross a block boundary. And we have
- // to carefully dodge no-op instructions.
- do {
- if (&*BBI == InstParent->begin()) {
- BasicBlock *Pred = InstParent->getSinglePredecessor();
- if (!Pred)
- goto decline_rv_optimization;
- BBI = Pred->getTerminator();
- break;
- }
- --BBI;
- } while (isNoopInstruction(BBI));
-
- if (&*BBI == GetObjCArg(Inst)) {
- DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
- "retainAutoreleasedReturnValue optimization.\n");
- Changed = true;
- InlineAsm *IA =
- InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
- /*isVarArg=*/false),
- RetainRVMarker->getString(),
- /*Constraints=*/"", /*hasSideEffects=*/true);
- CallInst::Create(IA, "", Inst);
- }
- decline_rv_optimization:
- 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);
-
- DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
- << " New = " << *Null << "\n");
-
- CI->replaceAllUsesWith(Null);
- CI->eraseFromParent();
- }
- continue;
- }
- case IC_Release:
- ContractRelease(Inst, I);
- continue;
- case IC_User:
- // Be conservative if the function has any alloca instructions.
- // Technically we only care about escaping alloca instructions,
- // but this is sufficient to handle some interesting cases.
- if (isa<AllocaInst>(Inst))
- TailOkForStoreStrongs = false;
- continue;
- default:
- continue;
- }
-
- DEBUG(dbgs() << "ObjCARCContract: Finished List.\n\n");
-
- // 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 the call's return value dominates a use of the call's argument
- // value, rewrite the use to use the return value. We check for
- // reachability here because an unreachable call is considered to
- // trivially dominate itself, which would lead us to rewriting its
- // argument in terms of its return value, which would lead to
- // infinite loops in GetObjCArg.
- if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
- Changed = true;
- Instruction *Replacement = Inst;
- Type *UseTy = U.get()->getType();
- if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
- // 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());
- // While we're here, rewrite all edges for this PHI, rather
- // than just one use at a time, to minimize the number of
- // bitcasts we emit.
- 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, "",
- cast<Instruction>(U.getUser()));
- 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;
- }
- }
-
- // If this function has no escaping allocas or suspicious vararg usage,
- // objc_storeStrong calls can be marked with the "tail" keyword.
- if (TailOkForStoreStrongs)
- for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
- E = StoreStrongCalls.end(); I != E; ++I)
- (*I)->setTailCall();
- StoreStrongCalls.clear();
-
- return Changed;
-}
-
-/// @}
-///
projects / oota-llvm.git / blobdiff