On Wed, Oct 30, 2013 at 6:42 PM, Uros Bizjak <ubiz...@gmail.com> wrote:
> On Wed, Oct 30, 2013 at 12:11 PM, Jakub Jelinek <ja...@redhat.com> wrote:
>
>>> > Yesterday I've noticed that for AVX which allows unaligned operands in
>>> > AVX arithmetics instructions we still don't combine unaligned loads with
>>> > the
>>> > AVX arithmetics instructions. So say for -O2 -mavx -ftree-vectorize
>>>
>>> This is actually PR 47754 that fell below radar for some reason...
>>
>> Apparently yes.
>>
>>> > the patch attempts to avoid gen_lowpart on the non-MEM lhs of the
>>> > unaligned
>>> > loads, which usually means combine will fail, by doing the load into a
>>> > temporary pseudo in that case and then doing a pseudo to pseudo move with
>>> > gen_lowpart on the rhs (which will be merged soon after into following
>>> > instructions).
>>>
>>> Is this similar to PR44141? There were similar problems with V4SFmode
>>> subregs, so combine was not able to merge load to the arithemtic insn.
>>
>> From the work on the vectorization last year I remember many cases where
>> subregs (even equal size) on the LHS of instructions prevented combiner or
>> other RTL optimizations from doing it's job. I believe I've changed some
>> easy places that did that completely unnecessarily, but certainly have not
>> went through all the code to look for other places where this is done.
>>
>> Perhaps let's hack up a checking pass that will after expansion walk the
>> whole IL and complain about same sized subregs on the LHS of insns, then do
>> make
>> check with it for a couple of ISAs (-msse2,-msse4,-mavx,-mavx2 e.g.?
>>
>>> > I'll bootstrap/regtest this on x86_64-linux and i686-linux, unfortunately
>>> > my
>>> > bootstrap/regtest server isn't AVX capable.
>>>
>>> I can bootstrap the patch later today on IvyBridge with
>>> --with-arch=core-avx-i --with-cpu=core-avx-i --with-fpmath=avx.
>>
>> That would be greatly appreciated, thanks.
>
> The bootstrap and regression test was OK for x86_64-linux-gnu {,-m32}.
>
> The failures in the attached report are either pre-existing or benign
> due to core-avx-i default to AVX.
I was referring to the *runtime* failures here.
> Please also mention PR44141 in the ChangeLog entry.
Ops, this should be PR47754.
Thanks,
Uros.
