Re: [BUG] PPC math-emu multiply problem

From: La Monte H.P. Yarroll
Date: Thu Jul 29 2004 - 14:51:48 EST


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. :-)


Thanks for doing the initial work!

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.


Indeed, when using this board for real we generally recommend
exactly the same thing.

Remember, don't mix soft-float compilation with libraries compiled
with HW floating point, and trap emulations. They are not
compatible and will return erroneous results.


Unfortunately, LSB does not provide a set of test binaries which
use the softfloat ABI, so in order to get an LSB-comformant distribution
on this CPU, we need to use floating point emulation. Interestingly,
this is the only LSB floating point test which fails.

--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell's sig


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/