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Re: Revisit Core tunning flags
- From: Wei Mi <wmi at google dot com>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: Xinliang David Li <davidxl at google dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, "H.J. Lu" <hjl dot tools at gmail dot com>
- Date: Sun, 22 Sep 2013 10:08:28 -0700
- Subject: Re: Revisit Core tunning flags
- Authentication-results: sourceware.org; auth=none
- References: <20130921195426 dot GA20274 at kam dot mff dot cuni dot cz> <CAAkRFZKtN7V2EOUrufLEWpexZc+MZiaz+u7DGAff9NMyc078DA at mail dot gmail dot com> <CAAkRFZKkY+BZjGLsp6EYs+BnShEHUGxDUtSk=TRG1=0YRbOy_g at mail dot gmail dot com> <20130922082624 dot GA4107 at atrey dot karlin dot mff dot cuni dot cz>
>> > http://gcc.gnu.org/ml/gcc-patches/2013-09/msg00884.html
>
> This patch seems resonable. (in fact I have pretty much same in my tree)
> use_vector_fp_converts is actually trying to solve the same problem in AMD
> hardware - you need to type the whole register when converting.
> So it may work well for AMD chips too or may be the difference is that
> Intel chips somehow handle "cvtpd2ps %xmm0, %xmm0" well even though
> the upper half of xmm0 is ill defined, while AMD chips doesn't.
>
> The patch seems OK. I do not see rason for
> && peep2_reg_dead_p (0, operands[0])
> test. Reg has to be dead since it is full destination of the operation.
Ok, I see. I will delete it.
>
> Lets wait few days before commit so we know effect of
> individual changes. I will test it on AMD hardware and we can decide on
> generic tuning then.
>
> Honza
Ok, thanks.
Wei Mi.