Re: compiling new-lib

[Jens-Christian Lache <lache at tu-harburg dot de>]

Am Die, 28 Nov 2000 schrieben Sie:
> Jens-Christian Lache wrote:
> > 
> > Does anybody know if the files from new-lib get compiled
> > with optimization -O2 turned on by default?
> > 
> > If I do a doublexdouble - multiplikation (64x64) on a ARM7TDMI proc,
> > I get times of 1160 Clock-Ticks per multiplikation.
> > 
> > Jens-Christian
> > 
> > --
> > 
> > Jens-Christian Lache
> > Technische Universitaet Hamburg-Harburg
> > www.tu-harburg.de/~sejl1601
> > Mail:
> > lache@tu-harburg.de
> > lache@ngi.de
> > Tel.:
> > +0491759610756
> 
> The default target flags are "-g -O2".  This does not affect multiplication, however.
> Code for the multiplication of doubles is part of the compiler.  
> 
> What options did you specify when compiling?  If your chip supports floating point, you 
> want to specify the -mhard-float option when you compile and link.  Linking via gcc allows
> you to specify this option so that the correct newlib library is linked in.
> 
> You should also note that the default newlib math library uses integer math.  If
> you want newlib to use floating-point algorithms, then configure with --enable-newlib-hw-fp.
> 
> -- Jeff Johnston
-- 

Hello!  I don't have a floating point unit.  What I have is a 32x8 Multiplier
using the booth algor.

I have benchmarked 32x32 multiplikation before. The results were:
 1.) no loop
(two Timer-Ticks correspond to one nop)
nb       Timer-Ticks 
of 
mult
0	4		(Measure overhead)
1	24
3	47
6	87
16	242
20	304
256	3965
512	7929
1024	15868
each mult consists of
ldr     r1, [fp, #-448]
ldr     r3, [fp, #-88]
mla     r9, r3, r1, r9
=> 15.5 Timer-Ticks/ (sum+=c[i]*samples[i])
2.) loop
If I put it in a loop, the assemble code is much larger:
.L15:
        mov     r3, r5, asl #2
        ldr     r1, [ip, r3]
        add     r5, r5, #1
        ldr     r2, [r0, r3]
        cmp     r5, #79
        mla     r7, r2, r1, r7
        ble     .L15
nb of       Timer-Ticks
mult
0	4
1	26
8	204
80	2040
300	7648
600	15297
800	20397
1024	26109
=> 25.5 Timer-Ticks/loop

These results look quite allright to me. If I have double instead of int
variables inside my loop, the results look like:
  0                26
  1            2319
  2	    5034
  4	  10413
  8	  21048
 16	  41986
 32	  83948	(with overhead bit set in TC_SR)

These values look so strange to me. Shouldn't a 64x64 multi
have the size of four 32x32 mult? Or is this normal?

Jens-Christian




Jens-Christian Lache
Technische Universitaet Hamburg-Harburg
www.tu-harburg.de/~sejl1601
Mail:
lache@tu-harburg.de
lache@ngi.de
Tel.:
+0491759610756