On Mon, 05 Feb 2018 20:24:45 -0500 Mark H Weaver <m...@netris.org> wrote:
> Hi Eric, > > Eric Bavier <ericbav...@centurylink.net> writes: > > > On Sat, 03 Feb 2018 22:55:56 -0500 > > Mark H Weaver <m...@netris.org> wrote: > > > >> ericbav...@centurylink.net (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. Sorry about the confusion. I'll revise it to something more informative. I usually try to refrain from "witty" comments. > > >> 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. AMD also had a 4-argument FMA instruction much sooner. Thank you for the attention to this matter, `~Eric