[X86] Fixes commit r214890 to match the posted patch

This was another fallout from my local rebase where something went wrong :(

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214951 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Switch to a formulation of a for loop that is much more obviously
not corrupting the mask by mutating it more times than intended. No
functionality changed (the results were non-overlapping so the old
version "worked" but was non-obvious).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214953 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Fix two independent miscompiles in the process of getting the same
test case to actually generate correct code.

The primary miscompile fixed here is that we weren't correctly handling
in-place elements in one half of a single-input v8i16 shuffle when
moving a dword of elements from that half to the other half. Some times,
we would clobber the in-place elements in forming the dword to move
across halves.

The fix to this involves forcibly marking the in-place inputs even when
there is no need to gather them into a dword, and to much more carefully
re-arrange the elements when grouping them into a dword to move across
halves. With these two changes we would generate correct shuffles for
the test case, but found another miscompile. There are also some random
perturbations of the generated shuffle pattern in SSE2. It looks like
a wash; more instructions in some cases fewer in others.

The second miscompile would corrupt the results into nonsense. This is
a buggy pattern in one of the added DAG combines. Mapping elements
through a PSHUFD when pairing redundant half-shuffles is *much* harder
than this code makes it out to be -- it requires reasoning about *all*
of where the input is used in the PSHUFD, not just one part of where it
is used. Plus, we can't combine a half shuffle *into* a PSHUFD but the
code didn't guard against it. I think this was just a bad idea and I've
just removed that aspect of the combine. No tests regress as
a consequence so seems OK.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214954 91177308-0d34-0410-b5e6-96231b3b80d8
[AArch64] Conditional selects are expensive on out-of-order cores.

Specifically Cortex-A57. This probably applies to Cyclone too but I haven't enabled it for that as I can't test it.

This gives ~4% improvement on SPEC 174.vpr, and ~1% in 471.omnetpp.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214957 91177308-0d34-0410-b5e6-96231b3b80d8
ARM-MachO: materialize callee address correctly on v4t.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214958 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: do not generate BLX instructions on Cortex-M CPUs.

Particularly on MachO, we were generating "blx _dest" instructions on M-class
CPUs, which don't actually exist. They happen to get fixed up by the linker
into valid "bl _dest" instructions (which is why such a massive issue has
remained largely undetected), but we shouldn't rely on that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214959 91177308-0d34-0410-b5e6-96231b3b80d8
Add a new option -run-slp-after-loop-vectorization.

This swaps the order of the loop vectorizer and the SLP/BB vectorizers. It is disabled by default so we can do performance testing - ideally we want to change to having the loop vectorizer running first, and the SLP vectorizer using its leftovers instead of the other way around.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214963 91177308-0d34-0410-b5e6-96231b3b80d8
[AArch64] Add a testcase for r214957.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214965 91177308-0d34-0410-b5e6-96231b3b80d8
Add a "probe-stack" attribute

This attribute is used to ensure the guard page is triggered on stack
overflow. Stack frames larger than the guard page size will generate a
call to __probestack to touch each page so the guard page won't be skipped.
[x86] Split out the logic to select the stack probe function
[x86] Please the whitespace gods
[x86] Add support for "probe-stack"
[x86] Fast-path for stack probes on smaller frames
Whitespace fixup
[ARM] Add support for "probe-stack"
[x86] Use ___chkstk_ms instead of ___chkstk on Cygwin/MinGW x64

This was done in X86FrameLowering, but not in X86TargetLowering.
Whitespace fixup