This is the mail archive of the
binutils@sources.redhat.com
mailing list for the binutils project.
Re: STUB_MOVE in elfxx-mips.c
cgd@broadcom.com writes:
> At 01 Oct 2003 09:38:17 -0700, Ian Lance Taylor wrote:
> > There was a processor from IDT which has this property.
>
> Could that be construed to say:
>
> "we should support doing it either way, depending on what CPU
> is being tuned for?"
>
> because if you're going to violate peoples' expectations to implement
> an optimization for a specific processor (which ultimately makes the
> assembler implementation more complex), then shouldn't you afford that
> opportunity for other processors?
Sure. As I said, it seemed to me at the time that `add' would never
be slower than `or', so it seemed reasonable to always use `add' as
the implementation of the `move' pseudo-op. Which is what the
assembler does today. And it still seems reasonable to me.
> No, I don't have a performance bias for either 'add' or 'or' for my
> parts. However, I do have a strong bias against code the implements
> things in violation of peoples expectations, and, most especially code
> that tells you that two things are the same, when they're not (e.g.,
> disassembler).
You're quite right about the disassembler. I would support a patch to
simply move the `move' pseudo-op to the end of the opcode table, so
that the move was disassembled as the actual instruction (and remove
the disassembly of `or' as `move'). This would presumably break the
testsuite somewhat.
Ian