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Re: 01/03: gnu: Add QD.
From: |
Mark H Weaver |
Subject: |
Re: 01/03: gnu: Add QD. |
Date: |
Mon, 05 Feb 2018 20:24:45 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) |
Hi Eric,
Eric Bavier <address@hidden> writes:
> On Sat, 03 Feb 2018 22:55:56 -0500
> Mark H Weaver <address@hidden> wrote:
>
>> address@hidden (Eric Bavier) writes:
>> > + `(#:configure-flags `("--disable-enable_fma" ;weird :/
>>
>> "weird :/" is not a very useful comment.
>
> Sorry. I thought it was obvious it was in reference to the
> "disable-enable" bit.
I thought that might be the case, but I was still curious why you were
disabling FMA support, and the comment didn't help.
>> Can you change it to explain
>> why you added this flag? It seems unfortunate to disable fused
>> multiply-add for this kind of library.
>
> The library does not support runtime ISA detection. I thought FMAs are
> something we don't support in our baseline x86-64 builds?
Indeed. I was surprised to learn that FMAs are only supported in very
recent Intel processors. My Yeeloong with MIPS-based Loongson 2F
processor from 2008 includes support for FMA instructions, and I guessed
that Intel had them long before, but actually Intel didn't add them
until several years later.
Mark