AArch64: make FastISel memcpy emission more robust.

We were hitting an assert if FastISel couldn't create the load or store we
requested. Currently this happens for large frame-local addresses, though
CodeGen could be improved there.

rdar://problem/17187463

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210519 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: teach FastISel how to handle offset FrameIndices

Previously we were abandonning the attempt, leading to some combination of
extra work (when selection of a load/store fails completely) and inferior code
(when this leads to a real memcpy call instead of inlining).

rdar://problem/17187463

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210520 91177308-0d34-0410-b5e6-96231b3b80d8
X86: elide comparisons after cmpxchg instructions.

The C++ and C semantics of the compare_and_swap operations actually
require us to return a boolean "success" value. In LLVM terms this
means a second comparison of the output of "cmpxchg" against the input
desired value.

However, x86's "cmpxchg" instruction sets all flags for the comparison
formed, so we can skip any secondary comparison. (N.b. this isn't true
for cmpxchg8b/16b, which only set ZF).

rdar://problem/13201607

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210523 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "X86: elide comparisons after cmpxchg instructions."

This reverts commit r210523. It was committed prematurely without waiting for
review.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210524 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: disallow x30 & x29 as the destination for indirect tail calls

As Ana Pazos pointed out, these have to be restored to their incoming values
before a function returns; i.e. before the tail call. So they can't be used
correctly as the destination register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210525 91177308-0d34-0410-b5e6-96231b3b80d8