Re: AW: [PATCH] Speed-up decimal formatting in *printf().

[Jonathan Larmour <jifl at eCosCentric dot com>]

[ Private mail, so sender omitted... ]
> > Sergei Organov wrote:
> > > The patch below boosts performance of decimal formatting of 
> > integers by
> > > roughly a factor of 2 on ARM7 CPU without hardware integer 
> > division. In
> > > fact it replaces integer modulo operation with multiply and 
> > subtract,
> > > that hopefully is either faster or roughly the same on all supported
> > > CPUs.
> > I agree. I've applied the patch, thanks!
>
> I think this patch could need a comment in the code, which explains why there's not simply a modulo.

Good idea. I've added this:
Index: src/output/vfnprintf.cxx
===================================================================
RCS file: 
/cvs/ecos/ecos/packages/language/c/libc/stdio/current/src/output/vfnprintf.cxx,v
retrieving revision 1.9
diff -u -5 -p -r1.9 vfnprintf.cxx
--- src/output/vfnprintf.cxx    22 Dec 2006 21:37:00 -0000      1.9
+++ src/output/vfnprintf.cxx    2 Jan 2007 11:53:12 -0000
@@ -553,10 +553,11 @@ number:                 if ((dprec = pre
                                         break;

                                 case DEC:
                                         /* many numbers are 1 digit */
                                         while (_uquad >= 10) {
+                                                /* The following is 
usually faster than using a modulo */
                                                 u_quad_t next = _uquad / 10;
                                                 *--cp = to_char(_uquad - 
(next * 10));
                                                 _uquad = next;
                                         }
                                         *--cp = to_char(_uquad);
Jifl
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