lib/Transforms/ObjCARC/ObjCARC.h

   1 //===- ObjCARC.h - ObjC ARC Optimization --------------*- C++ -*-----------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 /// \file
   9 /// This file defines common definitions/declarations used by the ObjC ARC
  10 /// Optimizer. ARC stands for Automatic Reference Counting and is a system for
  11 /// managing reference counts for objects in Objective C.
  12 ///
  13 /// WARNING: This file knows about certain library functions. It recognizes them
  14 /// by name, and hardwires knowledge of their semantics.
  15 ///
  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.
  19 ///
  20 //===----------------------------------------------------------------------===//
  21
  22 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
  23 #define LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
  24
  25 #include "llvm/ADT/StringSwitch.h"
  26 #include "llvm/Analysis/AliasAnalysis.h"
  27 #include "llvm/Analysis/ObjCARCAnalysisUtils.h"
  28 #include "llvm/Analysis/ObjCARCInstKind.h"
  29 #include "llvm/Analysis/Passes.h"
  30 #include "llvm/Transforms/Utils/Local.h"
  31 #include "llvm/Analysis/ValueTracking.h"
  32 #include "llvm/IR/CallSite.h"
  33 #include "llvm/IR/InstIterator.h"
  34 #include "llvm/IR/Module.h"
  35 #include "llvm/Pass.h"
  36 #include "llvm/Transforms/ObjCARC.h"
  37
  38 namespace llvm {
  39 class raw_ostream;
  40 }
  41
  42 namespace llvm {
  43 namespace objcarc {
  44
  45 /// Erase the given instruction.
  46 ///
  47 /// Many ObjC calls return their argument verbatim,
  48 /// so if it's such a call and the return value has users, replace them with the
  49 /// argument value.
  50 ///
  51 static inline void EraseInstruction(Instruction *CI) {
  52   Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
  53
  54   bool Unused = CI->use_empty();
  55
  56   if (!Unused) {
  57     // Replace the return value with the argument.
  58     assert((IsForwarding(GetBasicARCInstKind(CI)) ||
  59             (IsNoopOnNull(GetBasicARCInstKind(CI)) &&
  60              IsNullOrUndef(OldArg->stripPointerCasts()))) &&
  61            "Can't delete non-forwarding instruction with users!");
  62     CI->replaceAllUsesWith(OldArg);
  63   }
  64
  65   CI->eraseFromParent();
  66
  67   if (Unused)
  68     RecursivelyDeleteTriviallyDeadInstructions(OldArg);
  69 }
  70
  71 /// If Inst is a ReturnRV and its operand is a call or invoke, return the
  72 /// operand. Otherwise return null.
  73 static inline const Instruction *getreturnRVOperand(const Instruction &Inst,
  74                                                     ARCInstKind Class) {
  75   if (Class != ARCInstKind::RetainRV)
  76     return nullptr;
  77
  78   const auto *Opnd = Inst.getOperand(0)->stripPointerCasts();
  79   if (const auto *C = dyn_cast<CallInst>(Opnd))
  80     return C;
  81   return dyn_cast<InvokeInst>(Opnd);
  82 }
  83
  84 /// Return the list of PHI nodes that are equivalent to PN.
  85 template<class PHINodeTy, class VectorTy>
  86 void getEquivalentPHIs(PHINodeTy &PN, VectorTy &PHIList) {
  87   auto *BB = PN.getParent();
  88   for (auto &P : BB->phis()) {
  89     if (&P == &PN) // Do not add PN to the list.
  90       continue;
  91     unsigned I = 0, E = PN.getNumIncomingValues();
  92     for (; I < E; ++I) {
  93       auto *BB = PN.getIncomingBlock(I);
  94       auto *PNOpnd = PN.getIncomingValue(I)->stripPointerCasts();
  95       auto *POpnd = P.getIncomingValueForBlock(BB)->stripPointerCasts();
  96       if (PNOpnd != POpnd)
  97         break;
  98     }
  99     if (I == E)
 100       PHIList.push_back(&P);
 101   }
 102 }
 103
 104 } // end namespace objcarc
 105 } // end namespace llvm
 106
 107 #endif