Add a new ObjC ARC optimization pass to eliminate unneeded
autorelease push+pop pairs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148330 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 03b287f..87df838 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -375,7 +375,7 @@
}
// Otherwise, be conservative.
- return IC_User;
+ return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
}
/// IsRetain - Test if the the given class is objc_retain or
@@ -884,6 +884,122 @@
}
//===----------------------------------------------------------------------===//
+// ARC autorelease pool elimination.
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// ObjCARCAPElim - Autorelease pool elimination.
+ class ObjCARCAPElim : public ModulePass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool runOnModule(Module &M);
+
+ bool MayAutorelease(CallSite CS);
+ 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();
+}
+
+/// MayAutorelease - Interprocedurally determine if calls made by the
+/// given call site can possibly produce autoreleases.
+bool ObjCARCAPElim::MayAutorelease(CallSite CS) {
+ if (Function *Callee = CS.getCalledFunction()) {
+ if (Callee->isDeclaration() || Callee->mayBeOverridden())
+ return true;
+ for (Function::iterator I = Callee->begin(), E = Callee->end();
+ I != E; ++I) {
+ BasicBlock *BB = I;
+ for (BasicBlock::iterator J = BB->begin(), F = BB->end(); J != F; ++J)
+ if (CallSite JCS = CallSite(J))
+ if (!JCS.onlyReadsMemory() && MayAutorelease(JCS))
+ 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;
+ Inst->eraseFromParent();
+ Push->eraseFromParent();
+ }
+ Push = 0;
+ break;
+ case IC_CallOrUser:
+ if (MayAutorelease(CallSite(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;
+
+ bool Changed = false;
+
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+ Function *F = I;
+ // Only look at function definitions.
+ if (F->isDeclaration())
+ continue;
+ // Only look at global constructor functions. Unfortunately,
+ // the name is the most convenient way to recognize them.
+ if (!F->getName().startswith("_GLOBAL__I_"))
+ 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;
+}
+
+//===----------------------------------------------------------------------===//
// ARC optimization.
//===----------------------------------------------------------------------===//