sparc-rtems4.7-gcc versus fpu

[Joel Sherrill]

Ralf Corsepius wrote:
> On Tue, 2007-06-12 at 09:07 -0500, Joel Sherrill wrote:
>   
>> Peter A. Krauss wrote:
>>     
>>> Hello,
>>>
>>> I have downloaded sparc-rtems4.7 and would like to use it for a leon2 
>>> target with fpu. I am puzzled on how the compiler inserts fpu 
>>> instructions. My summary is:
>>>
>>> - The compiler does insert fpu instructions, if no fpu command line 
>>> option is given or if "-mhard-quad-float" is used.
>>>
>>> - The compiler does not insert fpu instructions, if "-mfpu" or 
>>> "-mhard-float" is used.
>>>
>>> Why?
>>>       
>> It would take a gcc expert to answer for sure but I recall a recent
>> discussion on the gcc list which sounds like it is happening here.
>> I suspect that since hard FPU is the default, -mfpu is toggling the
>> default and turning it into soft float.
>>
>> I tried this with gcc 4.2.0 and got your behavior.  I tried it with
>> the RTEMS 4.6 gcc 3.2.3 and it still generated hardware FPU instructions.
>>
>> Can you send this report to gcc AT gcc.gnu.org and CC me?  I think
>> someone over there will have a better answer.
>>     
>
> FWI: -msoft-float is supposed not to produce fpu instructions for
> sparc-rtems4.8-gcc. If this doesn't work, something is borked somewhere.
>
>   
If I followed the question correctly, -mcpu=cypress -mfpu should
still produce hardware FPU code, but doesn't.  It appears that
-mfpu is not toggling the FPU code generation bit not setting it.

--joel
> Ralf
>
>
>