diff options
| -rw-r--r-- | lib/Transforms/Scalar/ObjCARC.cpp | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp index e64c186..7e3e69b 100644 --- a/lib/Transforms/Scalar/ObjCARC.cpp +++ b/lib/Transforms/Scalar/ObjCARC.cpp @@ -898,7 +898,7 @@ bool ObjCARCExpand::runOnFunction(Function &F) { // 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. + // emitted here. We'll redo them in the contract pass. Changed = true; Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0)); break; @@ -1012,7 +1012,11 @@ bool ObjCARCAPElim::runOnModule(Module &M) { return false; // Find the llvm.global_ctors variable, as the first step in - // identifying the global constructors. + // 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; @@ -2278,6 +2282,7 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) { case IC_DestroyWeak: { CallInst *CI = cast<CallInst>(Inst); if (isNullOrUndef(CI->getArgOperand(0))) { + Changed = true; Type *Ty = CI->getArgOperand(0)->getType(); new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), Constant::getNullValue(Ty), @@ -2293,6 +2298,7 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) { CallInst *CI = cast<CallInst>(Inst); if (isNullOrUndef(CI->getArgOperand(0)) || isNullOrUndef(CI->getArgOperand(1))) { + Changed = true; Type *Ty = CI->getArgOperand(0)->getType(); new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), Constant::getNullValue(Ty), @@ -3180,6 +3186,8 @@ void ObjCARCOpt::MoveCalls(Value *Arg, } } +/// PerformCodePlacement - Identify pairings between the retains and releases, +/// and delete and/or move them. bool ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates, @@ -3193,6 +3201,7 @@ ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState> SmallVector<Instruction *, 4> NewReleases; SmallVector<Instruction *, 8> DeadInsts; + // Visit each retain. for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(), E = Retains.end(); I != E; ++I) { Value *V = I->first; @@ -3666,6 +3675,7 @@ bool ObjCARCOpt::doInitialization(Module &M) { if (!EnableARCOpts) return false; + // If nothing in the Module uses ARC, don't do anything. Run = ModuleHasARC(M); if (!Run) return false; @@ -4000,6 +4010,7 @@ void ObjCARCContract::ContractRelease(Instruction *Release, } bool ObjCARCContract::doInitialization(Module &M) { + // If nothing in the Module uses ARC, don't do anything. Run = ModuleHasARC(M); if (!Run) return false; @@ -4075,6 +4086,7 @@ bool ObjCARCContract::runOnFunction(Function &F) { --BBI; while (isNoopInstruction(BBI)) --BBI; if (&*BBI == GetObjCArg(Inst)) { + Changed = true; InlineAsm *IA = InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()), /*isVarArg=*/false), @@ -4124,6 +4136,13 @@ bool ObjCARCContract::runOnFunction(Function &F) { 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; @@ -4138,6 +4157,9 @@ bool ObjCARCContract::runOnFunction(Function &F) { 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) { |