I built GCC with the hard abi. The software ran fine but I see a performance
hit with the hard abi.
ABI: Test Execution Time (ms)
soft 1358
softfp 96
hard 109
I don't know why the hard is slower than the softfp. Here was my test code.
int ii;
uint32_t end_time, start_time;
double dvalue[8], dresult[20];
start_time = rtems_clock_get_ticks_since_boot();
for( ii = 0; ii < 20; ii++ )
{
dresult[ii] = 0.0;
}
dvalue[0] = 12.12;
dvalue[1] = 23.23;
dvalue[2] = 34.34;
dvalue[3] = 45.45;
dvalue[4] = 56.56;
dvalue[5] = 67.67;
dvalue[6] = 78.78;
dvalue[7] = 89.89;
for( ii = 0; ii < 10000; ii++ )
{
dresult[0] += (( dvalue[0] * dvalue[0] ) + ( dvalue[1] * dvalue[1] )
+ ( dvalue[2] * dvalue[2] ) + ( dvalue[3] * dvalue[3] ) +
( dvalue[4] * dvalue[4] ) + ( dvalue[5] * dvalue[5] ) + ( dvalue[6]
* dvalue[6] ) + ( dvalue[7] * dvalue[7] )) /
(( dvalue[0] / dvalue[1] ) - ( dvalue[1] / dvalue[2] ) - (
dvalue[2] / dvalue[3] ) - ( dvalue[3] / dvalue[4] ) -
( dvalue[4] / dvalue[5] ) - ( dvalue[5] / dvalue[6] ) - ( dvalue[6]
/ dvalue[7] ));
dresult[1] += cos( dvalue[0] * PI / 180.0 );
dresult[2] += sin( dvalue[1] * PI / 180.0 );
dresult[3] += tan( dvalue[2] * PI / 180.0 );
dresult[4] += acos( 1 / dvalue[3] ) * 180.0 / PI;
dresult[5] += asin( 1 / dvalue[4] ) * 180.0 / PI;
dresult[6] += atan( dvalue[5] ) * 180.0 / PI;
dresult[7] += atan2( dvalue[6], dvalue[7] ) * 180.0 / PI;
dresult[8] += cosh( 1 / dvalue[7] );
dresult[9] += sinh( dvalue[0] );
dresult[10] += tanh( dvalue[1] );
dresult[11] += acosh( dvalue[2] );
dresult[12] += asinh( dvalue[3] );
dresult[13] += atanh( 1 / dvalue[4] );
dresult[14] += exp( 1 / dvalue[5] );
dresult[15] += pow( dvalue[6], 1 / dvalue[7] );
dresult[16] += sqrt( dvalue[7] );
dresult[17] += log( dvalue[0] );
dresult[18] += log10( dvalue[1] );
dresult[19] += log2( dvalue[2] );
}
end_time = rtems_clock_get_ticks_since_boot();
for( ii = 0; ii < 20; ii++ )
{
printf( "dresult[%d] = %f\n", ii, dresult[ii] );
}
printf( "VFP Execution Time: %lu\n", end_time - start_time );
Kevin Kirspel
Electrical Engineer - Sr. Staff
Opti Medical
235 Hembree Park Drive
Roswell GA 30076
Tel: (770)-510-4444 ext. 81642
Direct: (770)-688-1642
Fax: (770)-510-4445
-----Original Message-----
From: Sebastian Huber [mailto:sebastian.hu...@embedded-brains.de]
Sent: Friday, August 19, 2016 8:56 AM
To: Kirspel, Kevin <kevin-kirs...@idexx.com>; devel@rtems.org
Subject: Re: [PATCH 1/2] RTEMS Source Builder changes for lpc32xx VFP support
On 19/08/16 14:39, Kirspel, Kevin wrote:
> This goes back 5 or more years ago so my recollection might be off but I had
> issues with GCC 4.5.2 using -mfloat-abi=hard. NXP recommends
> -mfloat-abi=softfp. I can't find the article or forum now but I think it had
> to do with the fact that the LPC3250 VFP didn't support all the required
> instructions for -mfloat-abi=hard (something about needing a Undefined
> Instruction exception handler to process unsupported VFP instructions).
> Using -mfloat-abi=softfp eliminates the need for the Undefined Instruction
> exception handler to handle unsupported VFP instructions.
The used VFP instructions should not depend on hard vs. softfp ABI since this
should only affect the calling conventions. In addition we use now GCC 6. Could
you please test with -mfloat-abi=hard. This is what all the other VFP multilibs
use.
--
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.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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