Port-powerpc archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: MKSOFTFLOAT for evbppc

Matt Thomas <matt%3am-software.com@localhost> writes:

> On Sep 20, 2012, at 8:31 PM, Simon Burge wrote:
>> Matt Thomas wrote:
>>>> (Also, for the port page: does fp emulation via traps work?  Or is
>>>> MKSOFTFLOAT the only way that can possibly work?)
>>> Within the past 4 months or so, I added emulation of the FPU so you can
>>> run without MKSOFTFLOAT=yes.
>> It looks like we've still got the same FPU emulator from the Walnut
>> (405GP) days.  Way back when (2001?), softfloat was orders of magnitude
>> faster on a Walnut.  There's the timings for an awk command issued
>> during a kernel build at the time:
>>      emulate:       113.554u 2778.750s 52:30.75 91.7%
>>      softfloat:       7.607u    1.447s  0:10.57 85.5%
>> This was the only reason we did softfloat at the time.
> On a P2020, a build.sh distribution for evbppc took 6.2% less time on
> a softfloat userland .vs. hardfloat userland with kernel-emulation.
> 10h55m32s (soft) vs. 11h38m50s (hard)

So it's good to hear that trapfloat (?) works (did you install that
build?), but 6% seems like enough that using softfloat is in order.
But, I see the point that having one userland usable on all evbppc is
nice, and perhaps not worth 6% in the standard distribution, since using
softfloat on machines with hardfloat (not trapfloat) is surely vastly

Attachment: pgpxfsfeqQpI7.pgp
Description: PGP signature

Home | Main Index | Thread Index | Old Index