diff options
Diffstat (limited to 'contrib/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp | 177 |
1 files changed, 0 insertions, 177 deletions
diff --git a/contrib/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp b/contrib/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp deleted file mode 100644 index b341dd807508..000000000000 --- a/contrib/llvm/lib/Transforms/ObjCARC/ObjCARCAPElim.cpp +++ /dev/null @@ -1,177 +0,0 @@ -//===- ObjCARCAPElim.cpp - ObjC ARC Optimization --------------------------===// -// -// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. -// See https://llvm.org/LICENSE.txt for license information. -// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception -// -//===----------------------------------------------------------------------===// -/// \file -/// -/// 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. -/// -/// This specific file implements optimizations which remove extraneous -/// autorelease pools. -/// -/// WARNING: This file knows about certain library functions. It recognizes them -/// by name, and hardwires knowledge 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. -/// -//===----------------------------------------------------------------------===// - -#include "ObjCARC.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/IR/Constants.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/raw_ostream.h" - -using namespace llvm; -using namespace llvm::objcarc; - -#define DEBUG_TYPE "objc-arc-ap-elim" - -namespace { - /// Autorelease pool elimination. - class ObjCARCAPElim : public ModulePass { - void getAnalysisUsage(AnalysisUsage &AU) const override; - bool runOnModule(Module &M) override; - - 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->hasExactDefinition()) - return true; - for (const BasicBlock &BB : *Callee) { - for (const Instruction &I : BB) - if (ImmutableCallSite JCS = ImmutableCallSite(&I)) - // 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 = nullptr; - for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { - Instruction *Inst = &*I++; - switch (GetBasicARCInstKind(Inst)) { - case ARCInstKind::AutoreleasepoolPush: - Push = Inst; - break; - case ARCInstKind::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; - LLVM_DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop " - "autorelease pair:\n" - " Pop: " - << *Inst << "\n" - << " Push: " << *Push - << "\n"); - Inst->eraseFromParent(); - Push->eraseFromParent(); - } - Push = nullptr; - break; - case ARCInstKind::CallOrUser: - if (MayAutorelease(ImmutableCallSite(Inst))) - Push = nullptr; - 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; - - if (skipModule(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 three-field structs 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 (std::next(F->begin()) != F->end()) - continue; - // Ok, a single-block constructor function definition. Try to optimize it. - Changed |= OptimizeBB(&F->front()); - } - - return Changed; -} |