[objc-arc] Teach the ARC optimizer that objc_sync_enter/objc_sync_exit do not modify the ref count of an objc object and additionally are inert for modref purposes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185769 91177308-0d34-0410-b5e6-96231b3b80d8
[objc-arc] Remove the alias analysis part of r185764.

Upon further reflection, the alias analysis part of r185764 is not a safe
change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185770 91177308-0d34-0410-b5e6-96231b3b80d8
SLPVectorizer: Implement DCE as part of vectorization.

This is a complete re-write if the bottom-up vectorization class.
Before this commit we scanned the instruction tree 3 times. First in search of merge points for the trees. Second, for estimating the cost. And finally for vectorization.
There was a lot of code duplication and adding the DCE exposed bugs. The new design is simpler and DCE was a part of the design.
In this implementation we build the tree once. After that we estimate the cost by scanning the different entries in the constructed tree (in any order). The vectorization phase also works on the built tree.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185774 91177308-0d34-0410-b5e6-96231b3b80d8
Add missing per-argument doesNotAccessMemory accessors. No functionality change
since it has no callers today.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185775 91177308-0d34-0410-b5e6-96231b3b80d8
Eliminate trivial redundant loads across nocapture+readonly calls to uncaptured
pointer arguments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185776 91177308-0d34-0410-b5e6-96231b3b80d8