cpuuse, rtmonuse and gcc (was: erc32 wrong compilation flags for initial task with fpu?)

[Jiri Gaisler]

This is pretty bad. If the kernel uses floats, then compilation
with -msoft-float will not work if the application later is linked
without -msoft-float. Are the CPU_usage_Dump() and Period_usage_Dump()
new functions or have they always been around? Are there other
functions in the kernel that uses floats as well?

Jiri.

Aleix Conchillo Flaqué wrote:
> Hi again,
> 
> I forced the SPARC_HAS_FPU to 1, so CPU_HARDWARE_FP is set to TRUE.
> Now (compiling RTEMS with -msoft-float), the CPU_usage_Dump and
> Period_usage_Dump print 0.000 for percentage values.
> 
> I have disassembled the code and I have seen that the compiler forces
> those functions (by chance, only these two) to use __floatsidf and
> __divdf3 functions, which I think are for software floating point
> emulation. This is fine, the problem is that they use floating point
> registers internally.
> 
> So, even RTEMS is compiled with -msoft-float, gcc floating point
> software emulation function use floating point registers, which is
> kind of scary.
> 
> Luckily, my task had the RTEMS_FLOATING_POINT attribute set, so I
> could see the statistics. Removing the attribute, which I think it
> should, crashed the application because of the gcc problem cited
> above.
> 
> The problems I am facing now are:
> 
> - gcc uses floating point registers for some floating point software
> emulation routines.
> - cpu_usage_dump and period_usage_dump do not print correct percentage
> values. I am not sure if this is caused by the point above.
> 
> Does this makes any sense at all?
> 
> 
> Aleix
> 
>