Messages in this thread Patch in this message | | | Date | Fri, 30 Jul 2004 11:23:22 -0400 | From | Greg Weeks <> | Subject | Re: [BUG] PPC math-emu multiply problem |
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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/
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