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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 <> 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.


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