Update Atomics.rst

Summary:
I changed various bits of the compilation of atomics recently, and forgot
updating the documentation. This patch just brings it up to date.

Test Plan: no change to the code

Reviewers: jfb

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5590

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218937 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Remove a test that provides little value. There are plenty of
tests for zext of a vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218939 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Remove a couple of other overly isolated tests that are low-value
at this point. We have lots of tests of peephole optimizations with
insert and extract on vectors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218940 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Regenerate a number of FileCheck assertions with my script for
test cases that will change with the new vector shuffle lowering. This
gives us a nice baseline for deltas against. I've checked and removed
the cases where there were weird register usage being pinned down, and
all of these are extremely pin-pointed tests so fully checking them
seems very appropriate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218941 91177308-0d34-0410-b5e6-96231b3b80d8
[BasicAA] Revert r218714 - Make better use of zext and sign information.

This patch broke 447.dealII on Darwin. I'm currently working on a reduced
test-case, but reverting for now to keep the bots happy.

<rdar://problem/18530107>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218944 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Merge two very similar tests and regenerate FileCheck lines for
them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218945 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] This is a terrible SSE1 test, but we should keep it. I've deleted
two functions that really didn't have any interesting assertions, and
generated more precise tests for one of the others.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218946 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Cleanup and generate precise FileCheck assertions for a bunch of
SSE tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218947 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Regenerate and clean up more tests is preparation for vector
shufle switch.

I nuked a win64 config from one test as it doesn't really make sense to
cover that ABI specially for generic v2f32 tests...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218948 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Remove an over-reduced test case. This would need to be
intergrated much more fully into some logical part of the backend to
really understand what it is trying to accomplish and how to update it.
I suspect it no longer holds enough value to be worth having.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218950 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Regenerate precise checks for a couple of test cases and remove
a test case that was just grepping the debug stats output rather than
actually checking the generated code for anything useful.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218951 91177308-0d34-0410-b5e6-96231b3b80d8