Re: Debian ports for RiscPC, ARM710, etc.
>So I suppose we are building binaries that use the halfword
>instructions. Is that correct?
Yes. If you use -march=armv4 (or -mcpu=strongarm110 which implies it) then
you will be using the halfword instructions.
>In the interests of portability, what would be the performance cost if
>we somehow compiled things without the halfword instructions? Do all
>apps benefit, or just some specific ones? Corel is using them for
>their RPM-based distribution, so I have assumed that there is a
>significant performance difference.
The halfword instructions probably do make a measurable difference. More to
the point the v4 architecture introduces instructions like UMULL which can
make even more of a difference and you can't (currently at least) selectively
enable these.
I don't think there's much to be gained from compiling the standard Debian
packages with backwards-compatibility options. The number of ARM machines
that can't run v4 binaries is fairly small and likely to stay that way. If
someone wanted to produce a CD with appropriate binaries for older machines
there would be nothing to stop them.
>I suppose I can lookup what flags to use from the source for the
>Linux/ARM distribution. Or maybe somebody could tell me?
-mcpu=arm6 will work on all v3 and later machines.
p.
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