Crash under sparc/rtems-4.11 when compiling with FPU

Athanasios.Tsiodras at Athanasios.Tsiodras at
Mon Feb 8 09:50:04 UTC 2016

I verified Sebastian's suggestion - by modifying the leon3.cfg file...

    diff --git a/c/src/lib/libbsp/sparc/leon3/make/custom/leon3.cfg 
    index 58f2f07..30fc3a4 100644
    --- a/c/src/lib/libbsp/sparc/leon3/make/custom/leon3.cfg
    +++ b/c/src/lib/libbsp/sparc/leon3/make/custom/leon3.cfg
    @@ -9,7 +9,8 @@ RTEMS_CPU_MODEL=leon3

     #  This contains the compiler options necessary to select the CPU 
     #  and (hopefully) optimize for it.
    -CPU_CFLAGS = -mcpu=cypress -msoft-float
    +CPU_CFLAGS = -mcpu=cypress -mhard-float

...the generated binary of hello.exe works fine - I went a step further 
and did a test calculation, too:

    diff --git a/testsuites/samples/hello/init.c 
    index d8fe450..6ee33f6 100644
    --- a/testsuites/samples/hello/init.c
    +++ b/testsuites/samples/hello/init.c
    @@ -27,8 +27,13 @@ rtems_task Init(
       rtems_task_argument ignored
    +  int i = 0;
    +  float a=3.14159f, b=1.0f;
    -  printf( "Hello World\n" );
    +  for (i=0; i<10; i++)
    +      b*=a;
    +  printf( "Hello World, %f\n", b );
       exit( 0 );

...which worked fine:

    (gdb) tar extended-remote ... ( to grmon)
    (gdb) c

    Hello World, 1.000000

...and I made sure that FPU instructions are inside:

      for (i=0; i<10; i++)
      28:   82 80 7f ff     addcc  %g1, -1, %g1
      2c:   12 bf ff ff     bne  28 <Init+0x28>
      30:   91 a2 09 29     fmuls  %f8, %f9, %f8
      printf( "Hello World, %f\n", b );
      34:   91 a0 19 28     fstod  %f8, %f8

So, executive summary....  It seems that the default compilation settings 
of the Leon3 BSP forbid "real FPU" work. 
If one needs to work in native (non-emulated) FPU mode, then the leon3.cfg 
must be patched as I showed above. 

In the long run, as Sebastian indicated, a leon3fp (and a corresponding 
leon2fp, I imagine) 
should ideally be added as new BSP targets - and the FPU page
should probably 
be updated to indicate this.

Thanks to everyone for their help,

European Space Agency (via HE Space)
Thanassis Tsiodras
Real-time Embedded Software Engineer 
System, Software and Technology Department

Keplerlaan 1, PO Box 299
NL-2200 AG Noordwijk, The Netherlands
Athanasios.Tsiodras at |
T +31 71 565 5332

From:   "Sebastian Huber" <sebastian.huber at>
To:     "RTEMS List" <users at>
Cc:     software at
Date:   07/02/2016 07:40
Subject:        Re: Crash under sparc/rtems-4.11 when compiling with FPU
Sent by:        "users" <users-bounces at>

Hello Athanasios,

it was always a miracle to me how you are supposed to use the leon2/leon3 
BSPs with a FPU. If you want to use the FPU, then the BSP must be built 
with the -mhard-float option, otherwise the FPU support is not enabled in 
the operating system support. In addition the application configuration 
must be compiled with exactly the same compiler flags as the BSP, 
otherwise it will generate a corrupt configuration.

I think we need leon2fp and leon3fp BSPs, which use -mhard-float.

Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at
PGP     : Public key available on request.

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