This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH][RFC][x86] Fix PR91154, add SImode smax, allow SImode add in SSE regs


On 7/27/19 3:22 AM, Uros Bizjak wrote:
> On Wed, Jul 24, 2019 at 5:03 PM Jeff Law <law@redhat.com> wrote:
> 
>>> Clearly this approach will run into register allocation issues
>>> but it looks cleaner than writing yet another STV-like pass
>>> (STV itself is quite awkwardly structured so I refrain from
>>> touching it...).
>>>
>>> Anyway - comments?  It seems to me that MMX-in-SSE does
>>> something very similar.
>>>
>>> Bootstrapped on x86_64-unknown-linux-gnu, previous testing
>>> revealed some issue.  Forgot that *add<mode>_1 also handles
>>> DImode..., fixed below, re-testing in progress.
>> Certainly simpler than most of the options and seems effective.
>>
>> FWIW, I think all the STV code is still disabled and has been for
>> several releases.  One could make an argument it should get dropped.  If
>> someone wants to make something like STV work, they can try again and
>> hopefully learn from the problems with the first implementation.
> 
> Huh?
> 
> STV code is *enabled by default* on 32bit SSE2 targets, and works
> surprisingly well (*) for DImode arithmetic, logic and constant shift
> operations. Even 32bit multilib on x86_64 is built with STV.
I must be mis-remembering or confusing it with something else.  Sorry
for any confusion.

Jeff


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]