Subject: Re: [linux-audio-dev] next power of two
From: Jack O'Quin (joq_AT_io.com)
Date: Thu Sep 18 2003 - 19:25:17 EEST
Taybin Rutkin <taybin_AT_earthlink.net> writes:
> Heh, that doesn't sound very RISC-like to me...
He called them "functions", not "instructions". I don't recall any
such instructions back back when I worked on PowerPC. But, providing
fast subroutine linkage for stuff like this is *very* RISC-like. It's
really fundamental to the RISC approach.
Many people misunderstand RISC. The goal is not to "reduce" the
number of instructions. PowerPC has *lots* of instructions. The
intent is to reduce the time required for all the frequently-used
instructions to one fast clock cycle.
Please forgive the long-winded reply, Taybin. I worked on this stuff
for many years, and I still love it. :-)
> -----Original Message-----
> From: Maarten de Boer <mdeboer_AT_iua.upf.es>
> Sent: Sep 18, 2003 7:41 AM
> To: linux-audio-dev_AT_music.columbia.edu
> Subject: Re: [linux-audio-dev] next power of two
>
> By the way, it seems the PPC has instructions to do it.
> >From the "PPC compiler writers guide":
>
> Round Up or Down to Next Power of 2
>
> The floor power of 2 ( flp2) and ceiling power of 2 ( clp2) functions
> are similar to the floor and ceiling functions, respectively, but they
> round to an integral power of 2, rather than to an integer.
>
Regards,
-- Jack O'Quin Austin, Texas, USA
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