[X86] Refactor X86ISelDAGToDAG::SelectAtomicLoadArith - NFC

Summary:
Mostly renaming the (not very explicit) variables Tmp0, .. Tmp4, and grouping
related statements together, along with a few lines of comments for the
surprising parts.

No functional change intended.

Test Plan: make check-all

Reviewers: jfb

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5088

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216768 91177308-0d34-0410-b5e6-96231b3b80d8
Relax the constraint more in MemoryDependencyAnalysis.cpp

Even loads/stores that have a stronger ordering than monotonic can be safe.
The rule is no release-acquire pair on the path from the QueryInst, assuming that
the QueryInst is not atomic itself.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216771 91177308-0d34-0410-b5e6-96231b3b80d8
typo


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216773 91177308-0d34-0410-b5e6-96231b3b80d8
another typo


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216774 91177308-0d34-0410-b5e6-96231b3b80d8
X86: Fix conflict over ESI between base register and rep;movsl

The new solution is to not use this lowering if there are any dynamic
allocas in the current function. We know up front if there are dynamic
allocas, but we don't know if we'll need to create stack temporaries
with large alignment during lowering. Conservatively assume that we will
need such temporaries.

Reviewed By: hans

Differential Revision: http://reviews.llvm.org/D5128

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216775 91177308-0d34-0410-b5e6-96231b3b80d8
Remove spurious mask operations from AArch64 add->compares on 16 and 8 bit values

This patch checks for DAG patterns that are an add or a sub followed by a
compare on 16 and 8 bit inputs. Since AArch64 does not support those types
natively they are legalized into 32 bit values, which means that mask operations
are inserted into the DAG to emulate overflow behaviour. In many cases those
masks do not change the result of the processing and just introduce a dependent
operation, often in the middle of a hot loop.

This patch detects the relevent DAG patterns and then tests to see if the
transforms are equivalent with and without the mask, removing the mask if
possible. The exact mechanism of this patch was discusses in
http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-July/074444.html

There is a reasonably good chance there are missed oppurtunities due to similiar
(but not identical) DAG patterns that could be funneled into this test, adding
them should be simple if we see test cases.

Tests included.

rdar://13754426

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216776 91177308-0d34-0410-b5e6-96231b3b80d8