lkml.org 
[lkml]   [2004]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [BUG] PPC math-emu multiply problem
Greg Weeks wrote:

> Dan Malek wrote:
>
>>
>> On Jul 29, 2004, at 10:06 AM, Kumar Gala wrote:
>>
>>>
>>> On Jul 29, 2004, at 8:14 AM, Greg Weeks wrote:
>>>
>>>> I'm seeing what appears to be a bug in the ppc kernel trap math
>>>> emulator. An extreme case for multiplies isn't working the way gcc
>>>> soft-float or hardware floating point is.
>>>
>>>
>>
>> I'm not surprised. I lifted this code from Sparc, glibc, and adapted
>> it as best I could for PPC years ago for the 8xx. I was happy when
>> it appeared to work for the general cases. :-)
>>
>> Due to its overhead, I never expected it to be _the_ solution for
>> processors that don't have floating point hardware. Recompiling
>> the libraries with soft-float and using that option when compiling
>> is the way to go.
>
>
> OK, this patch fixes my multiply problem with the LSB test. I still
> need to test to make sure I didn't break anything else, but it appears
> the rounding is only used when converting back to IEEE format. Is
> there some reason this is something really dumb to do?
>
When I actually built a kernel rather than just my test code the
FP_ROUNDMODE is picked up from the linux/math-emu/soft-fp.h. I don't
want to change the common definition unless I'm sure this is the correct
solution.

Signed-off-by: Greg Weeks <greg.weeks@timesys.com> under TS0087

--- tanith-linux-2.6.6/arch/ppc/math-emu/soft-fp.h.orig 2004-07-30
10:31:34.000000000 -0400
+++ tanith-linux-2.6.6/arch/ppc/math-emu/soft-fp.h 2004-07-30
11:18:59.000000000 -0400
@@ -14,9 +14,8 @@
# define FP_RND_ZERO 1
# define FP_RND_PINF 2
# define FP_RND_MINF 3
-#ifndef FP_ROUNDMODE
-# define FP_ROUNDMODE FP_RND_NEAREST
-#endif
+#undef FP_ROUNDMODE
+# define FP_ROUNDMODE FP_RND_ZERO
#endif

#define _FP_ROUND_NEAREST(wc, X) \
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:04    [W:1.142 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site