> "Correct" usage would be to enable those three instructions
> with a "-mcpu=nevada", or better still, "-mcpu=r5200" (for
> consistency), and to enable the rest of the MIPS IV ISA
> with "-mips4" instead of the archaic r8000 hack.
I should add "Correct", but not useful for 32-bit
kernels. "-mips32", once that percolates through
the gcc food chain, would be *almost* perfect
for 32-bit Nevada kernels. I say almost, because
while MIPS32 is 32-bit MIPS IV plus MADD, it also
has a handfull of instructions that are not supported
by the R52xx, of which it is wildly improbable but
theoretically possible that the multiply-subtracts
might somehow get emitted in compiled application
code. It should work just fine for kernel purposes, though.
Meanwhile, try piping objdump of a "-mmad" kernel
through "grep -i mad". I'd be stunned if a single MADD
turned up. If it gains nothing, but breaks builds, then
for heaven's sake banish -mmad from the kernel
makefiles!
Regards,
Kevin K.
