Am Dienstag, 26. September 2006 22:23 schrieb Wolfgang Grandegger:
> Niklaus Giger wrote:
> > Am Dienstag, 26. September 2006 18:28 schrieb Wolfgang Grandegger:
> >> Philippe Gerum wrote:
> >>> On Tue, 2006-09-26 at 16:56 +0200, gilles.chanteperdrix wrote:
> >>
> >> OK, but in general, soft-float emulation should be used on systems
> >> without FPU and this is even more important for real-time. This is a
> >> tool chain issue. Niklaus, what tool chain are you using?
> >
> > In my .config I have
> > MATH_EMULATION=y
>
> You seem to need that because your compiler generates code with hard FP
> instructions. You could check this with:
>
>   $ ppc-linux-objdump -d prog|egrep ":\s*[e-f]"
This does not return any match on my system.

But looking at the disassembly of the latency program I have code like:
100081bc <_restfpr_28_x>:
100081bc:       cb 8b ff e0     lfd     f28,-32(r11)
or
1000798c <__floatsidf>:
1000798c:       7c 08 02 a6     mflr    r0
10007990:       2f 83 00 00     cmpwi   cr7,r3,0
10007994:       94 21 ff c0     stwu    r1,-64(r1)
10007998:       90 01 00 44     stw     r0,68(r1)
1000799c:       54 60 0f fe     rlwinm  r0,r3,1,31,31
100079a0:       90 01 00 14     stw     r0,20(r1)
100079a4:       40 9e 00 24     bne-    cr7,100079c8 <__floatsidf+0x3c>

> > The toolchain is gcc-3.4.4-glibc-2.3.5/powerpc-405-linux-gnu built using
> > Dan Kegel crosstool (Version 0.42 if I remember exactly).
> >
> > Shall I switch to another one?
>
> The ELDK from DENX uses FP soft-emulation for 4xx (http://www.denx.de).
> Choose  v3.1.1 for Linux 2.4 and v4 for Linux 2.6.

I am breathing only PowerPC code on my Mac PowerBook (running Debian) and 
never managed to installed ELDK on it. (And even Detlev as a Debian developer 
couldn't recommend a simple way.) 

But I assume that I specifying GLIBC_EXTRA_CONFIG="--without-fp" in the 
powerpc-405.dat should be enough to make Dan Kegels crosstool emit Soft-FPU 
emulation.

I will try to run the tests at work where I have installed ELDK 4.0, but not 
yet a fully working environment. Therefore it may take some time to report a 
result back.

-- 
Niklaus Giger

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