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| author | Michael Gottesman <mgottesman@apple.com> | 2013-04-03 02:57:24 +0000 |
|---|---|---|
| committer | Michael Gottesman <mgottesman@apple.com> | 2013-04-03 02:57:24 +0000 |
| commit | a67a20c95f08b31b499d06d1fa47bdf14f9d40d0 (patch) | |
| tree | f06bdd22f1809d7c7bc82828b878617814f359d8 /lib/Support/Host.cpp | |
| parent | 003d5f946d3ad44cb42f7d25b0c40f04e9a5a0a2 (diff) | |
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
Diffstat (limited to 'lib/Support/Host.cpp')
0 files changed, 0 insertions, 0 deletions