Some free or "MIPS-like" CPUs don't implement it because of a patent
problem. I've seen at least one implementation on opencores.org that has
this (missing) feature.
Probably if the compiler were to emit lwl and lwr code via
__attribute__((packed)), these instructions would have to be emulated by
the kernel on such a CPU. I imagine this would be quite a bit worse than
just doing two normal loads and extracting the desired word.
On Tue, May 20, 2003 at 06:32:31PM +0000, Gilad Benjamini wrote:
> About two months ago there was a discussion
> here about disabling lwl-lwr.
> Can someone shed some light on why the discussion
> emerged ?
> Is this a performance issue, a processor which
> doesn't support it, or something else ?
> If this is a performance issue, I'll be happy
> to hear more details.