sparc-rtems4.7-gcc versus fpu
stephan.gruenfelder at space.at
Wed Jun 13 08:38:10 UTC 2007
I agree with Joel that this is not an RTEMS topic. The answer most likely is the
-mv8 option of gcc, which enables the FPU. However, if you compile mission
critical code for the AT697E (AT697E-2E-E), then you might want to turn off the
FPU anyway, because of a Multiplier/Divider failure in the LEON2 VHDL model (see
errata sheet of the AT697).
Joel Sherrill wrote:
> Peter A. Krauss wrote:
>> 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.
> 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.
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