ObjC ARC Optimizer.
The main implication of this is:
1. Ensuring that we treat it conservatively in terms of optimization.
2. We put the ASM marker on it so that the runtime can recognize
objc_unsafeClaimAutoreleasedReturnValue from releaseRV.
<rdar://problem/21567064>
Patch by Michael Gottesman!
llvm-svn: 258970
Specifically:
1. Added checks that unwind is being properly added to various instructions.
2. Fixed the declaration/calling of objc_release to have a return type of void.
3. Moved all checks to precede the functions and added checks to ensure that the
checks would only match inside the specific function that we are attempting to
check.
llvm-svn: 179973
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.
llvm-svn: 178612
The reason that this occurs is that tail calling objc_autorelease eventually
tail calls -[NSObject autorelease] which supports fast autorelease. This can
cause us to violate the semantic gaurantees of __autoreleasing variables that
assignment to an __autoreleasing variables always yields an object that is
placed into the innermost autorelease pool.
The fix included in this patch works by:
1. In the peephole optimization function OptimizeIndividualFunctions, always
remove tail call from objc_autorelease.
2. Whenever we convert to/from an objc_autorelease, set/unset the tail call
keyword as appropriate.
*NOTE* I also handled the case where objc_autorelease is converted in
OptimizeReturns to an autoreleaseRV which still violates the ARC semantics. I
will be removing that in a later patch and I wanted to make sure that the tree
is in a consistent state vis-a-vis ARC always.
Additionally some test cases are provided and all tests that have tail call marked
objc_autorelease keywords have been modified so that tail call has been removed.
*NOTE* One test fails due to a separate bug that I am going to commit soon. Thus
I marked the check line TMP: instead of CHECK: so make check does not fail.
llvm-svn: 172287
John McCall