Crash under sparc/rtems-4.11 when compiling with FPU
Hugues Jérôme
hugues.jerome at gmail.com
Mon Feb 8 11:14:14 UTC 2016
Hi,
The root of the wiki you point to is:
To Be Removed <https://devel.rtems.org/wiki/TBR#ToBeRemoved>
All pages under /TBR/* are slated to be removed.
If memory serves me, these were created when ritems.org has been reorganized.
Note sure it is a good idea to change this
> Le 8 févr. 2016 à 10:57, Athanasios.Tsiodras at esa.int a écrit :
>
> (slight correction - I pasted the wrong output, the binary works fine :-)
>
> *** BEGIN OF TEST HELLO WORLD ***
> Hello World, 93647.304688
> *** END OF TEST HELLO WORLD ***
>
> I am unaware of the proper etiquette for this, so I better check - am I allowed to edit the wiki page at https://devel.rtems.org/wiki/TBR/UserManual/Floating_Point_Support <https://devel.rtems.org/wiki/TBR/UserManual/Floating_Point_Support> to add a section about Leon3 native FPU usage and the need for the patch I did in leon3.cfg?
>
> Apologies if I am overstepping - I just don't want others to go through the same efforts that I did.
>
> Kind regards,
> Thanassis.
>
> European Space Agency (via HE Space)
> Thanassis Tsiodras
> Real-time Embedded Software Engineer
> System, Software and Technology Department
>
> ESTEC
> Keplerlaan 1, PO Box 299
> NL-2200 AG Noordwijk, The Netherlands
> Athanasios.Tsiodras at esa.int | www.esa.int <x-msg://320/www.esa.int>
> T +31 71 565 5332
>
>
>
> From: Athanasios.Tsiodras at esa.int
> To: "RTEMS List" <users at rtems.org>
> Date: 08/02/2016 10:50
> Subject: Re: Crash under sparc/rtems-4.11 when compiling with FPU
> Sent by: "users" <users-bounces at rtems.org>
>
>
>
> I verified Sebastian's suggestion - by modifying the leon3.cfg file...
>
> diff --git a/c/src/lib/libbsp/sparc/leon3/make/custom/leon3.cfg b/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 model
> # 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 b/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;
> +
> rtems_test_begin();
> - printf( "Hello World\n" );
> + for (i=0; i<10; i++)
> + b*=a;
> + printf( "Hello World, %f\n", b );
> rtems_test_end();
> exit( 0 );
> }
>
> ...which worked fine:
>
> (gdb) tar extended-remote ... ( to grmon)
> (gdb) c
> Continuing.
>
> *** BEGIN OF TEST HELLO WORLD ***
> Hello World, 1.000000
> *** END OF TEST HELLO WORLD ***
>
> ...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
> b*=a;
> 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
> (https://devel.rtems.org/wiki/TBR/UserManual/Floating_Point_Support <https://devel.rtems.org/wiki/TBR/UserManual/Floating_Point_Support>) should probably
> be updated to indicate this.
>
> Thanks to everyone for their help,
> Thanassis.
>
>
> European Space Agency (via HE Space)
> Thanassis Tsiodras
> Real-time Embedded Software Engineer
> System, Software and Technology Department
>
> ESTEC
> Keplerlaan 1, PO Box 299
> NL-2200 AG Noordwijk, The Netherlands
> Athanasios.Tsiodras at esa.int | www.esa.int <x-msg://320/www.esa.int>
> T +31 71 565 5332
>
>
>
> From: "Sebastian Huber" <sebastian.huber at embedded-brains.de>
> To: "RTEMS List" <users at rtems.org>
> Cc: software at gaisler.com
> Date: 07/02/2016 07:40
> Subject: Re: Crash under sparc/rtems-4.11 when compiling with FPU
> Sent by: "users" <users-bounces at rtems.org>
>
>
>
> 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 embedded-brains.de
> PGP : Public key available on request.
>
> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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