[PATCH-v2] sparc: Rename NGMP to GR740 and add configs for UT699, UT700, and GR712RC

[Sebastian Huber]

On 19/07/17 22:35, Jiri Gaisler wrote:

>
> On 07/19/2017 07:36 PM, Sebastian Huber wrote:
>> ----- Jiri Gaisler <jiri at gaisler.se> schrieb:
>>> On 07/19/2017 04:04 PM, Sebastian Huber wrote:
>>>> Hello Jiri,
>>>>
>>>> I fixed a couple of tests. One remaining failure on the leon2 is mathf:
>>>>
>>>> *** BEGIN OF TEST MATHF ***
>>>> acosf          : 1.570796
>>>> acoshf         : -nan
>>>> asinf          : 1.570796
>>>> asinhf         : 0.881374
>>>> atanf          : 0.665774
>>>> atan2f         : 0.785398
>>>> atanhf         : inf
>>>> cbrtf          : 3.000000
>>>> ceilf          : 4.000000
>>>> copysignf      : -3.500000
>>>> cosf           : -0.000000
>>>> coshf          : 2.509179
>>>> erff           : 1.000000
>>>> erfcf          : 0.000000
>>>> expf           : 1.521962
>>>> exp2f          : 1.337928
>>>> expm1f         : 0.000420
>>>> fabsf          : 1.123000
>>>> fdimf          : 0.000000
>>>> floorf         : 0.000000
>>>> floorf         : -1.000000
>>>>
>>>> Breakpoint 1, 0x40004044 in fmaf (x=x at entry=2.0999999, y=2.20000005,
>>>> z=3.00999999) at
>>>> /home/EB/sebastian_h/archive/gcc-git/newlib/libm/common/sf_fma.c:25
>>>> 25        return (float) (((double) x * (double) y) + (double) z);
>>>> (gdb) disas 0x40004044
>>>> Dump of assembler code for function fmaf:
>>>>     0x40004024 <+0>:     add  %sp, -80, %sp
>>>>     0x40004028 <+4>:     st  %o1, [ %sp + 0x4c ]
>>>>     0x4000402c <+8>:     ld  [ %sp + 0x4c ], %f8
>>>>     0x40004030 <+12>:    st  %o0, [ %sp + 0x4c ]
>>>>     0x40004034 <+16>:    ld  [ %sp + 0x4c ], %f9
>>>>     0x40004038 <+20>:    st  %o2, [ %sp + 0x4c ]
>>>>     0x4000403c <+24>:    fsmuld  %f8, %f9, %f0
>>>>     0x40004040 <+28>:    ld  [ %sp + 0x4c ], %f8
>>>> => 0x40004044 <+32>:    fstod  %f8, %f8
>>>>     0x40004048 <+36>:    add  %sp, 0x50, %sp
>>>>     0x4000404c <+40>:    faddd  %f0, %f8, %f0
>>>>     0x40004050 <+44>:    retl
>>>>     0x40004054 <+48>:    fdtos  %f0, %f0
>>>> End of assembler dump.
>>>> (gdb) p/x $fsr
>>>> $1 = 0xe660
>>>>
>>>> Is fstod implemented on the SIS?
>>> fstod is implemented.
>>>   
>>> The instruction that takes the trap is at 0x40004040, which is ld  [ %sp
>>> + 0x4c ], %f8. Remember that SPARC has deferred FPU trap model so it is
>>> actually the previous FPU instruction FSMULD at 0x4000403c that
>>> generated the trap. This instruction is not implemented in sis, and I am
>>> not sure it is even implemented in some leon2/leon3 hardware. I will
>>> check and report back ...
>>>
>>> Jiri.
>>>
>> I use -mcpu=leon -mfix-at697f and according to the manual we have:
>>
>> The AT697F floating-point unit is based on the MEIKO core and implements the SPARC floating-point instruction-set defined in the SPARC Architecture Manual version 8.
> I am certain that AT697E did not implement FSMULD, whether AT697F does
> it I do not know but I doubt it. On the other hand, most (all?) leon3
> with an FPU does support FSMULD. Maybe somebody with an AT697F board
> could run the MATHF test and report if it runs or traps. I will add
> fsmuld support to sis, but we should really try to find out if it is
> appropriate for leon2.
>
> Jiri.

Yes, we probably have to test this on real hardware, since according to 
the SPARC v8 manual we have:

"Appendix G — SPARC ABI Software Considerations

FsMULd instruction

The floating-point
multiply single-to-double instruction (FsMULd) is new in Version 8 of 
the SPARC
architecture.  Some SPARC systems in the field emulate this instruction in
software.

Recommended use of FsMULd instruction in SPARC ABI programs:

* If FsMULd is used infrequently (on a dynamic basis):
   Use the FsMULd instruction in-line.
* If FsMULd is used heavily (on a dynamic basis), and reasonable perfor-
   mance across all systems is preferred over optimal performance on the 
fastest
   systems: Convert the operands to double precision in scratch 
registers, then
   calculate the result with the FMULd instruction.  For example,
     fsmuld  %f20,%f21,%f8
   might be replaced by:
     fstod   %f20,%f0
     fstod   %f23,%f2
     fmuld   %f0,%f2,%f8
   This provides reasonable performance on machines with hardware 
support for
   FsMULd, while not penalizing those without it with the overhead of 
trap- ping
   and emulating the instructions in supervisor software.

* If FsMULd is used heavily (on a dynamic basis), and optimal performance
   on systems which implement FsMULd in hardware is desired at the cost of
   performance degradation on most systems: Use the FsMULd instruction 
in-line."

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
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