Merging r228444:

Merging r228444:
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r228444 | eugenis | 2015-02-06 13:47:39 -0800 (Fri, 06 Feb 2015) | 8 lines

[msan] Fix "missing origin" in atomic store.

An atomic store always make the target location fully initialized (in the
current implementation). It should not store origin. Initialized memory can't
have meaningful origin, and, due to origin granularity (4 bytes) there is a
chance that this extra store would overwrite meaningfull origin for an adjacent
location.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@228445 91177308-0d34-0410-b5e6-96231b3b80d8