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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 | b8c8836594f75280ff7f632846e8f48c027afabe (patch) | |
| tree | e48a0f7bae0b62904eebb6f457f2a8e37e0bf4b1 /llvm/lib/CodeGen/MachineModuleInfoImpls.cpp | |
| parent | bcd06c0220b2e3524aeefa4a7bf8f7f8d83db706 (diff) | |
| download | bcm5719-llvm-b8c8836594f75280ff7f632846e8f48c027afabe.tar.gz bcm5719-llvm-b8c8836594f75280ff7f632846e8f48c027afabe.zip | |
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.
llvm-svn: 178612
Diffstat (limited to 'llvm/lib/CodeGen/MachineModuleInfoImpls.cpp')
0 files changed, 0 insertions, 0 deletions
