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Re: [PATCH 2/2] Add leon3r0 and leon3r0v7 CPU targets
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Daniel Cederman <cederman at gaisler dot com>
- Cc: gcc-patches at gcc dot gnu dot org, daniel at gaisler dot com
- Date: Fri, 03 Jul 2015 12:54:42 +0200
- Subject: Re: [PATCH 2/2] Add leon3r0 and leon3r0v7 CPU targets
- Authentication-results: sourceware.org; auth=none
- References: <1435062156-28097-1-git-send-email-cederman at gaisler dot com> <12709888 dot UIjZx8BEIv at polaris> <55928E17 dot 2060101 at gaisler dot com>
> Thank you for the patch in your other mail that changes this!
You're welcome.
> We were also thinking of the instruction timing information found in the
> leon_costs and leon3_costs. We took a look at the values in leon_costs
> and they seem to fit well with the UT699, except for division. We got a
> bit unsure as to what leon system they are based on, as the division
> cost was wrong also for the AT697F, which is the most common leon2
> system. Would it be ok to update the division cost values of leon_costs
> so that they match UT699 and AT697F?
Sure.
> In general, depending on how one instantiate a leon system and which FPU
> is selected, you will get different timing. Is there a recommended way
> of adding support for this without adding additional CPU targets?
> We are considering to add support for GRFPU-lite, which only differs in
> the timing.
One could add a -mtune-fpu switch. Did you look at other architectures in the
GCC tree that would have similar requirements?
--
Eric Botcazou