[PATCHv2 6/7, GCC, ARM, V8M] ARMv8-M Security Extension's cmse_nonsecure_call: use __gnu_cmse_nonsecure_call

[Kyrill Tkachov]

And CC'ing Ramana and Richard this time...

On 11/11/16 16:18, Kyrill Tkachov wrote:
>
> On 11/11/16 16:15, Andre Vieira (lists) wrote:
>>> Why are you writing 1.0 to clear the register? I think you want
>>> CONST0_RTX (DFmode)
>>> and CONST0_RTX (SFmode).
>>>
>>> Also, in this function when you iterate from regno = 0 up to some
>>> number, please use
>>> regno = R0_REGNUM (minor nit).
>>>
>>> Thanks,
>>> Kyrill
>>>
>>>
>> Hi Kyrill,
>>
>> So you got me thinking there. I couldn't quite remember why I had chosen
>> 1.0 rather than 0 to clear the FP registers. I now know it is because
>> vmov (immediate) will not take 0.0, it does take 1.0.
>
> Ah, you're right (I checked it too).
>
>>   I made the other
>> changes you suggested and changed the vmovs in the library function
>> wrapper back to #1.0. I also removed the second register for the single
>> precision FP clearing, since the vmov from two general registers to two
>> single precision registers can take the same general register twice,
>> saving on a mov. There is a discrepancy there with the way I clear other
>> FP registers, there I do use 0, since I'd need two moves(or a move and a
>> shift) to encode 1.0 into a general purpose register, so I made a
>> conscious choice of performance over consistency there.
>
> Hmm, I'll defer to Ramana or Richard on whether we should keep consistent between SP and DP
> in libgcc/config/arm/cmse_nonsecure_call.S.
> Otherwise the patch looks good to me.
> Until this patch is approved by an arm maintainer can you please do a bootstrap and regtest
> on an arm-none-linux-gnueabihf target of all the patches in the series.
>
> Thanks,
> Kyrill
>> Again no changes to ChangeLog.
>>
>> Cheers,
>> Andre
>