PowerPC compilation flags

[Segher Boessenkool]

Hello Felipe,

On Sun, Nov 25, 2018 at 02:42:10PM -0500, Felipe GM wrote:
> Currently I am developing for a MPC5777 board, with e200z7 cores. Most 
> of the things are going well, but I am stuck with a problem that is 
> really annoying me already. I am trying to use floating point operations 
> on portions of my code, using the embedded hardware support. My 
> toolchain is GCC 6.3 (powerpc-gcc, although I have tried with 7.3 and 
> 8.2 too), for which I am using the following flags:

GCC 6 is no longer maintained.  GCC 8 powerpc*-* does not support SPE
anymore (you need to configure for powerpc*-*spe* instead; you probably
want that for GCC 6 and GCC 7 as well).

> |ASFLAGS_BASE =-g -a32 -mbooke -me500 --fatal-warnings ARCH_FLAGS 
> =-mpowerpc-gpopt -mfprnd -misel -m32 -mhard-float-mabi=spe -mmfpgpr 
> -mfloat-gprs=single|

-mpowerpc-gpopt, -mfprnd, -mmfpgpr, and -mhard-float do not make sense
for your target.

> Please notice the|-mfloat-gprs=single|flag. That is the one that is 
> giving problems.
> 
> When I use|-mfloat-gprs=single|, I am not able to compile things 
> properly, as some functions are not implemented:
> 
> |undefined reference to `__extendsfdf2`,undefined reference to 
> `__adddf3`,undefined reference to `__divdf3`,|
> 
> - among others.

That works fine for me (those functions are in libgcc.a).

Please open a PR for GCC 7 (and GCC 8).


Segher