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[ts-7000] Re: floating point emulation and old abi

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Subject: [ts-7000] Re: floating point emulation and old abi
From: "charliem_1216" <>
Date: Mon, 01 Jun 2009 05:05:41 -0000
--- In  "j.chitte" <> wrote:
>
> --- In  "j.chitte" <j.chitte@> wrote:
> >
> > Hi,
> > 
> > I have build a working 2.6.29 kernel using Matthieu's patchset. It was 
> > built with old abi compatibility.
> > 
> > I don't think I should have any old abi stuff floating about now so I 
> > wanted to rebuild it eabi only since this should be more effiecient.
> > 
> > However , when I disabled OABI_COMPAT the floating point menu gets 
> > disabled. I just see:
> >   *** At least one emulation must be selected *** 
> > 
> > Does this make sense or is it a glitch in kconfig :?

I think it is a glitch, and hasn't been updated for the eabi-only case.

> > 
> > TIA.
> >
> 
> Ah! 
>  Depends on: !AEABI || OABI_COMPAT   
> 
> So does that mean I have to rely on using Maverick in order to run eabi only?

No, maverick is completely separate.  Remember, the kernel uses no FP at all; 
what you are configuring here is which FPU emulator to build into the kernel.  

OABI needs an emulator in the kernel, since userspace FP is done by the kernel 
trapping & emulating hardfloat instructions.  That's what makes floating point 
under OABI so slow.  EABI doesn't need an emulator because userspace programs 
use softfloat (no illegal instruction trapping & emulation needed).

If you configure AEAB and OABI_COMPAT, then you still have to include a FPU 
choice in the kernel (for the OABI side).

regards, ......... Charlie

> 
> Help says I must have some sort of FPE even if there is an FPU.
> 
> thx
>




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