From a67a20c95f08b31b499d06d1fa47bdf14f9d40d0 Mon Sep 17 00:00:00 2001 From: Michael Gottesman Date: Wed, 3 Apr 2013 02:57:24 +0000 Subject: Remove an optimization where we were changing an objc_autorelease into an objc_autoreleaseReturnValue. The semantics of ARC implies that a pointer passed into an objc_autorelease must live until some point (potentially down the stack) where an autorelease pool is popped. On the other hand, an objc_autoreleaseReturnValue just signifies that the object must live until the end of the given function at least. Thus objc_autorelease is stronger than objc_autoreleaseReturnValue in terms of the semantics of ARC* implying that performing the given strength reduction without any knowledge of how this relates to the autorelease pool pop that is further up the stack violates the semantics of ARC. *Even though objc_autoreleaseReturnValue if you know that no RV optimization will occur is more computationally expensive. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178612 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/ObjCARC/ObjCARCOpts.cpp | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-) (limited to 'lib/Transforms/ObjCARC') diff --git a/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/lib/Transforms/ObjCARC/ObjCARCOpts.cpp index a956caeffe0..5ac8c8e6c27 100644 --- a/lib/Transforms/ObjCARC/ObjCARCOpts.cpp +++ b/lib/Transforms/ObjCARC/ObjCARCOpts.cpp @@ -1440,8 +1440,7 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) { break; } - // objc_autorelease(x), objc_autoreleaseRV -> objc_release(x) if x is - // otherwise unused. + // objc_autorelease(x) -> objc_release(x) if x is otherwise unused. if (IsAutorelease(Class) && Inst->use_empty()) { CallInst *Call = cast(Inst); const Value *Arg = Call->getArgOperand(0); @@ -2861,20 +2860,6 @@ void ObjCARCOpt::OptimizeReturns(Function &F) { DependingInstructions.clear(); Visited.clear(); - // Convert the autorelease to an autoreleaseRV, since it's - // returning the value. - if (AutoreleaseClass == IC_Autorelease) { - DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease " - "=> autoreleaseRV since it's returning a value.\n" - " In: " << *Autorelease - << "\n"); - Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent())); - DEBUG(dbgs() << " Out: " << *Autorelease - << "\n"); - Autorelease->setTailCall(); // Always tail call autoreleaseRV. - AutoreleaseClass = IC_AutoreleaseRV; - } - // Check that there is nothing that can affect the reference // count between the retain and the call. // Note that Retain need not be in BB. -- cgit v1.2.3