Akira Hatanaka 6fdcb3c2ce [ObjCARC] Do not move a release between a call and a ...

retainAutoreleasedReturnValue that retains the returned value.

This commit fixes a bug in ARC optimizer where it moves a release
between a call and a retainAutoreleasedReturnValue, causing the returned
object to be released before the retainAutoreleasedReturnValue can
retain it.

This commit accomplishes that by doing a lookahead and checking whether
the call prevents the release from moving upwards. In the long term, we
should treat the region between the retainAutoreleasedReturnValue and
the call as a critical section and disallow moving anything there
(possibly using operand bundles).

rdar://problem/20449878

llvm-svn: 301724

2017-04-29 00:23:11 +00:00

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