On Tue, Jul 30, 2002 at 06:28:32PM -0400, Zajerko-McKee, Nick wrote:
> I'm trying to write some inline assembler code that needs the madd and mulu
> op codes found on the 4KC processor. I've tried setting the cpu to 4650,
> but it failed to recognize the mulu instruction. Can someone give me the
> magic incantation? I'm running right now GCC 2.95.3 from Montavista. I
> guess one way I can attack it for now is to build the op code by hand, but
> that is quite dirty, IMHO...
That's an inconsistence in the MIPS instruction set. The old two operand
multiply instruction exists as both signed and unsigned (mult / multu)
but the new-style signed multiply only in an unsigned flavour. In other
words, there is no mulu instruction.
I guess the reason was that this instruction is mainly used for DSP-style
stuff which need signed arithmetics while burning valuable space in the
instruction set for a mulu instruction wasn't considered worth the