1 //===- ObjCARCUtil.cpp - ObjC ARC Optimization --------*- mode: c++ -*-----===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This file defines several utility functions used by various ARC
11 /// optimizations which are IMHO too big to be in a header file.
13 /// WARNING: This file knows about certain library functions. It recognizes them
14 /// by name, and hardwires knowledge of their semantics.
16 /// WARNING: This file knows about how certain Objective-C library functions are
17 /// used. Naive LLVM IR transformations which would otherwise be
18 /// behavior-preserving may break these assumptions.
20 //===----------------------------------------------------------------------===//
23 #include "llvm/IR/Intrinsics.h"
26 using namespace llvm::objcarc;
28 raw_ostream &llvm::objcarc::operator<<(raw_ostream &OS,
29 const InstructionClass Class) {
32 return OS << "IC_Retain";
34 return OS << "IC_RetainRV";
36 return OS << "IC_RetainBlock";
38 return OS << "IC_Release";
40 return OS << "IC_Autorelease";
41 case IC_AutoreleaseRV:
42 return OS << "IC_AutoreleaseRV";
43 case IC_AutoreleasepoolPush:
44 return OS << "IC_AutoreleasepoolPush";
45 case IC_AutoreleasepoolPop:
46 return OS << "IC_AutoreleasepoolPop";
48 return OS << "IC_NoopCast";
49 case IC_FusedRetainAutorelease:
50 return OS << "IC_FusedRetainAutorelease";
51 case IC_FusedRetainAutoreleaseRV:
52 return OS << "IC_FusedRetainAutoreleaseRV";
53 case IC_LoadWeakRetained:
54 return OS << "IC_LoadWeakRetained";
56 return OS << "IC_StoreWeak";
58 return OS << "IC_InitWeak";
60 return OS << "IC_LoadWeak";
62 return OS << "IC_MoveWeak";
64 return OS << "IC_CopyWeak";
66 return OS << "IC_DestroyWeak";
68 return OS << "IC_StoreStrong";
70 return OS << "IC_CallOrUser";
72 return OS << "IC_Call";
74 return OS << "IC_User";
75 case IC_IntrinsicUser:
76 return OS << "IC_IntrinsicUser";
78 return OS << "IC_None";
80 llvm_unreachable("Unknown instruction class!");
83 InstructionClass llvm::objcarc::GetFunctionClass(const Function *F) {
84 Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
86 // No (mandatory) arguments.
88 return StringSwitch<InstructionClass>(F->getName())
89 .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
90 .Case("clang.arc.use", IC_IntrinsicUser)
91 .Default(IC_CallOrUser);
94 const Argument *A0 = AI++;
96 // Argument is a pointer.
97 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
98 Type *ETy = PTy->getElementType();
100 if (ETy->isIntegerTy(8))
101 return StringSwitch<InstructionClass>(F->getName())
102 .Case("objc_retain", IC_Retain)
103 .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
104 .Case("objc_retainBlock", IC_RetainBlock)
105 .Case("objc_release", IC_Release)
106 .Case("objc_autorelease", IC_Autorelease)
107 .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
108 .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
109 .Case("objc_retainedObject", IC_NoopCast)
110 .Case("objc_unretainedObject", IC_NoopCast)
111 .Case("objc_unretainedPointer", IC_NoopCast)
112 .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
113 .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
114 .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
115 .Default(IC_CallOrUser);
118 if (PointerType *Pte = dyn_cast<PointerType>(ETy))
119 if (Pte->getElementType()->isIntegerTy(8))
120 return StringSwitch<InstructionClass>(F->getName())
121 .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
122 .Case("objc_loadWeak", IC_LoadWeak)
123 .Case("objc_destroyWeak", IC_DestroyWeak)
124 .Default(IC_CallOrUser);
127 // Two arguments, first is i8**.
128 const Argument *A1 = AI++;
130 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
131 if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
132 if (Pte->getElementType()->isIntegerTy(8))
133 if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
134 Type *ETy1 = PTy1->getElementType();
135 // Second argument is i8*
136 if (ETy1->isIntegerTy(8))
137 return StringSwitch<InstructionClass>(F->getName())
138 .Case("objc_storeWeak", IC_StoreWeak)
139 .Case("objc_initWeak", IC_InitWeak)
140 .Case("objc_storeStrong", IC_StoreStrong)
141 .Default(IC_CallOrUser);
142 // Second argument is i8**.
143 if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
144 if (Pte1->getElementType()->isIntegerTy(8))
145 return StringSwitch<InstructionClass>(F->getName())
146 .Case("objc_moveWeak", IC_MoveWeak)
147 .Case("objc_copyWeak", IC_CopyWeak)
148 // Ignore annotation calls. This is important to stop the
149 // optimizer from treating annotations as uses which would
150 // make the state of the pointers they are attempting to
151 // elucidate to be incorrect.
152 .Case("llvm.arc.annotation.topdown.bbstart", IC_None)
153 .Case("llvm.arc.annotation.topdown.bbend", IC_None)
154 .Case("llvm.arc.annotation.bottomup.bbstart", IC_None)
155 .Case("llvm.arc.annotation.bottomup.bbend", IC_None)
156 .Default(IC_CallOrUser);
160 return IC_CallOrUser;
163 /// \brief Determine what kind of construct V is.
165 llvm::objcarc::GetInstructionClass(const Value *V) {
166 if (const Instruction *I = dyn_cast<Instruction>(V)) {
167 // Any instruction other than bitcast and gep with a pointer operand have a
168 // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
169 // to a subsequent use, rather than using it themselves, in this sense.
170 // As a short cut, several other opcodes are known to have no pointer
171 // operands of interest. And ret is never followed by a release, so it's
172 // not interesting to examine.
173 switch (I->getOpcode()) {
174 case Instruction::Call: {
175 const CallInst *CI = cast<CallInst>(I);
176 // Check for calls to special functions.
177 if (const Function *F = CI->getCalledFunction()) {
178 InstructionClass Class = GetFunctionClass(F);
179 if (Class != IC_CallOrUser)
182 // None of the intrinsic functions do objc_release. For intrinsics, the
183 // only question is whether or not they may be users.
184 switch (F->getIntrinsicID()) {
185 case Intrinsic::returnaddress: case Intrinsic::frameaddress:
186 case Intrinsic::stacksave: case Intrinsic::stackrestore:
187 case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
188 case Intrinsic::objectsize: case Intrinsic::prefetch:
189 case Intrinsic::stackprotector:
190 case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
191 case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
192 case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
193 case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
194 case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
195 case Intrinsic::invariant_start: case Intrinsic::invariant_end:
196 // Don't let dbg info affect our results.
197 case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
198 // Short cut: Some intrinsics obviously don't use ObjC pointers.
204 return GetCallSiteClass(CI);
206 case Instruction::Invoke:
207 return GetCallSiteClass(cast<InvokeInst>(I));
208 case Instruction::BitCast:
209 case Instruction::GetElementPtr:
210 case Instruction::Select: case Instruction::PHI:
211 case Instruction::Ret: case Instruction::Br:
212 case Instruction::Switch: case Instruction::IndirectBr:
213 case Instruction::Alloca: case Instruction::VAArg:
214 case Instruction::Add: case Instruction::FAdd:
215 case Instruction::Sub: case Instruction::FSub:
216 case Instruction::Mul: case Instruction::FMul:
217 case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
218 case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
219 case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
220 case Instruction::And: case Instruction::Or: case Instruction::Xor:
221 case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
222 case Instruction::IntToPtr: case Instruction::FCmp:
223 case Instruction::FPTrunc: case Instruction::FPExt:
224 case Instruction::FPToUI: case Instruction::FPToSI:
225 case Instruction::UIToFP: case Instruction::SIToFP:
226 case Instruction::InsertElement: case Instruction::ExtractElement:
227 case Instruction::ShuffleVector:
228 case Instruction::ExtractValue:
230 case Instruction::ICmp:
231 // Comparing a pointer with null, or any other constant, isn't an
232 // interesting use, because we don't care what the pointer points to, or
233 // about the values of any other dynamic reference-counted pointers.
234 if (IsPotentialRetainableObjPtr(I->getOperand(1)))
238 // For anything else, check all the operands.
239 // Note that this includes both operands of a Store: while the first
240 // operand isn't actually being dereferenced, it is being stored to
241 // memory where we can no longer track who might read it and dereference
242 // it, so we have to consider it potentially used.
243 for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
245 if (IsPotentialRetainableObjPtr(*OI))
250 // Otherwise, it's totally inert for ARC purposes.