On 02/18/2003 Izumi Tsutsui wrote:
>
> What do you mean "backward compatible on Sh4"?
> AFAIK, instruction sets between SH3 and SH4 are mostly same
> at least on userland. Most instructions added on SH4 are
> for the privileged mode (cache control etc.)

The FPU seems to be SH4 only. I just noticed that only if I compile a
program using floats with the -m4 parameter, fpu opcodes are actually
generated. Without -m4 it's all subroutine calls. (Btw, with -m4
doesn't build a functional program, some different subroutines are
missing.)

Also I found this line in cpu_getmcontext
(sys/arch/sh3/sh3/sh3_machdep.c):

-------
/* FPU context is currently not handled by the kernel. */
memset(&mcp->__fpregs, 0, sizeof (mcp->__fpregs));
-------

It seems the FPU isn't used by NetBSD/dreamcast :-(

regards,
chris