Re: adding movz to machine description

[Ian Lance Taylor <iant at google dot com>]

"Petar Bajic" <petar.bajic@micronasnit.com> writes:

> > It may be correct for the pattern to not be matched with expand.  It's
> > OK if the if-conversion pass picks it up, which seems to be what is
> > happening for you.
> >
> > If the generated code you are getting is wrong, then problem is likely
> > in the define_insn patterns somewhere.  They don't correct represent
> > what the instruction does, or they don't correctly implement it.
> >
> > Ian
> 
> After some modifications, I managed to make gcc use my define_expand -
> I see it in debug.11.ce1 and following files, but then it disapears in
> debug.17.combine, and in the end it does not appear in asm code. How
> to find out what kills it? :)

That means that the combine pass has replaced it with something else
which is equivalent which the combine pass thought would be cheaper.
Look at the generated RTL to see what it turned into.  If the
resulting code is less efficient to run, then you need to adjust your
costs (the TARGET_RTX_COSTS hook).

Ian