* Optimal compile flags for ultra2 & power2
@ 1998-09-21 20:09 Stephen Hocking-Senior Programmer PGS Tensor Perth
1998-09-21 22:52 ` David S. Miller
1998-09-22 9:00 ` David Edelsohn
0 siblings, 2 replies; 5+ messages in thread
From: Stephen Hocking-Senior Programmer PGS Tensor Perth @ 1998-09-21 20:09 UTC (permalink / raw)
To: egcs
I was wondering what flags people use for best FP performance on these -
a) Sun ultra2
b) IBM Power2.
There's an additional quirk - a lot of the data I have to work with is 32bit
FP, so avoiding costly conversions between double & single precision (which is
a characteristic of the Power2 chipset) is important.
Stephen
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Optimal compile flags for ultra2 & power2
1998-09-21 20:09 Optimal compile flags for ultra2 & power2 Stephen Hocking-Senior Programmer PGS Tensor Perth
@ 1998-09-21 22:52 ` David S. Miller
1998-09-22 9:51 ` John Carr
1998-09-22 9:00 ` David Edelsohn
1 sibling, 1 reply; 5+ messages in thread
From: David S. Miller @ 1998-09-21 22:52 UTC (permalink / raw)
To: shocking; +Cc: egcs
Date: Tue, 22 Sep 1998 11:09:03 +0800
From: Stephen Hocking-Senior Programmer PGS Tensor Perth <shocking@prth.pgs.com>
I was wondering what flags people use for best FP performance on these -
a) Sun ultra2
-O2 -mtune=ultrasparc -fcall-used-g4 -fcall-used-g5 -fcall-used-g7
Later,
David S. Miller
davem@dm.cobaltmicro.com
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Optimal compile flags for ultra2 & power2
1998-09-21 20:09 Optimal compile flags for ultra2 & power2 Stephen Hocking-Senior Programmer PGS Tensor Perth
1998-09-21 22:52 ` David S. Miller
@ 1998-09-22 9:00 ` David Edelsohn
1 sibling, 0 replies; 5+ messages in thread
From: David Edelsohn @ 1998-09-22 9:00 UTC (permalink / raw)
To: Stephen Hocking-Senior Programmer PGS Tensor Perth; +Cc: egcs
>>>>> Stephen Hocking-Senior Programmer PGS Tensor Perth writes:
Stephen> I was wondering what flags people use for best FP performance on these -
Stephen> b) IBM Power2.
-mcpu=rios2 -ffast-math -lrs2
Make sure that -ffast-math is safe for your application -- it is a general
GCC optimization. /usr/lib/librs2.a is an additional math library
provided by IBM that substitutes the hardware fsqrt instruction for the
library sqrt call and all places that it is used.
David
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Optimal compile flags for ultra2 & power2
1998-09-21 22:52 ` David S. Miller
@ 1998-09-22 9:51 ` John Carr
1998-09-23 0:49 ` David S. Miller
0 siblings, 1 reply; 5+ messages in thread
From: John Carr @ 1998-09-22 9:51 UTC (permalink / raw)
To: David S. Miller; +Cc: shocking, egcs
> I was wondering what flags people use for best FP performance on these -
>
> a) Sun ultra2
>
> -O2 -mtune=ultrasparc -fcall-used-g4 -fcall-used-g5 -fcall-used-g7
%g7 is used by the Solaris thread library, so don't use -fcall-used-g7
in multithreaded programs (which includes any program using XIL in
Solaris 2.6).
-mcpu=ultrasparc will enable the V9 floating point instructions and
should improve performance on an Ultra; code compiled with this switch
will not run on older SPARCs.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Optimal compile flags for ultra2 & power2
1998-09-22 9:51 ` John Carr
@ 1998-09-23 0:49 ` David S. Miller
0 siblings, 0 replies; 5+ messages in thread
From: David S. Miller @ 1998-09-23 0:49 UTC (permalink / raw)
To: jfc; +Cc: shocking, egcs
Date: Tue, 22 Sep 1998 12:50:57 EDT
From: John Carr <jfc@MIT.EDU>
> I was wondering what flags people use for best FP performance on these -
>
> a) Sun ultra2
>
> -O2 -mtune=ultrasparc -fcall-used-g4 -fcall-used-g5 -fcall-used-g7
%g7 is used by the Solaris thread library, so don't use -fcall-used-g7
in multithreaded programs (which includes any program using XIL in
Solaris 2.6).
Right, and if it is non-threaded you can add -fcall-used-g6 as well.
Thanks for pointing this out.
-mcpu=ultrasparc will enable the V9 floating point instructions and
should improve performance on an Ultra; code compiled with this switch
will not run on older SPARCs.
I get enough egcs-1.1 compiler crashes and bad code-gen reports about
-mcpu=ultrasparc that I fail to recommend it any more. Hopefully I
can stabilize this in the main line soon...
Later,
David S. Miller
davem@dm.cobaltmicro.com
^ permalink raw reply [flat|nested] 5+ messages in thread
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1998-09-21 20:09 Optimal compile flags for ultra2 & power2 Stephen Hocking-Senior Programmer PGS Tensor Perth
1998-09-21 22:52 ` David S. Miller
1998-09-22 9:51 ` John Carr
1998-09-23 0:49 ` David S. Miller
1998-09-22 9:00 ` David Edelsohn
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