On Sat, 9 Mar 2002, Todd Vierling wrote:

> On Sun, 10 Mar 2002, matthew green wrote:
>
> :    [note: -mcpu=v8 means the resulting code will not run on sparc v7 and
> :    older systems.]
> :
> : this isn't true; we emulate these instructions in the kernel.
>
> However, it's ungodly slow, since the emulation makes the already slow
> sun4's and sun4c's have to do even more work.
>
> : /etc/ld.so.conf work needs to be done for sparc.
>
> Yes.  I've already said precisely what needs to be done in the past to make
> this less grotty, and it's pretty simple, but I simply don't have the

In the mean time are these details sufficient enough to compose a chapter
for "The NetBSD Guide" on optimizing for different ports (at least i386,
sparc, etc. where there are CPUs of different steppings) ?

-lava

> machinery in easy reach to test it on the varying architectures:
>
> * A flag indicating presence of v8 instructions needs to be in the machdep
>   sysctl tree.  I don't know if there is one there already capable of being
>   used in ld.so.conf.
>
> * Given the above, a small `libc_v8.so', in the vein of `libm387.so' for
>   i386, can be created that simply contains the v8 instruction replacements
>   for the libcalls:
>
>   .mul    .umul    .div    .udiv    .rem    .urem
>
> * ld.so.conf can be shipped by default with a libc override, such as:
>
>   libc.so.12       machdep.v8_present       1:libc_v8.so.0,libc.so.12
>
> With all of the above, you gain *nearly* all the speed all around for v8
> instructions on sun4m and sun4u-32 architectures (modulo the overhead of
> layering libc_v8 on libc), without hosing speed for the same binaries on v7
> systems.
>
> --
> -- Todd Vierling <tv@wasabisystems.com>  *  Wasabi & NetBSD:  Run with it.
> -- CDs, Integration, Embedding, Support -- http://www.wasabisystems.com/
>

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