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Re: [ts-7000] Re: Floating point

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Subject: Re: [ts-7000] Re: Floating point
From: Lennert Buytenhek <>
Date: Sun, 26 Mar 2006 11:14:14 +0200
On Sat, Mar 25, 2006 at 02:28:41AM -0000, Yan Seiner wrote:

> > Are you using crunch, hardfpa, softvfp, something else?
> 
> I don't know....  I am using the standard 2.4 ts-9 kernel floating
> point....

Right.

FPA is the floating point coprocessor that nobody has anymore, but
gcc emits code for by default (if you use hard-float), and the linux
kernel emulates (nwfpe/fastfpe.)

The ep93xx have a hardware floating point coprocessor, which is called
MaverickCrunch or simply crunch.

You can also ask gcc to do all floating point computations 'in software'
(i.e. without using a hardware floating point coprocessor or trapping to
the linux kernel.)  This is called soft-float.  When in this mode, there
are two possible word orders it can use: FPA word ordering (which is
compatible with the FPA coprocessor, where the byte order is native-endian
(so that's little-endian on LE ep93xx systems) but big-endian word order),
and VFP word ordering (which is fully native byte and word ordering.)

So, since there are so many possibilities, whenever there is a floating
point problem on an ARM box the first problem is to find out which floating
point method is actually being used!

Which gcc version are you using?  Do a "gcc -dumpspecs" and then check
what it gives for "multilib_defaults".  This is from a big-endian IXP
box running debian:

        *multilib_defaults:
        marm mbig-endian mhard-float mapcs-32 mno-thumb-interwork


--L


 
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