adding movz to machine description

[Rask Ingemann Lambertsen]

On Fri, Jul 07, 2006 at 04:25:08PM +0200, Petar Bajic wrote:
> but my "movz" look like this
> 
> if (c == 0)
>    a = b;
> 
> or asm: movz r1, r2, r3  ;; ((if r3 == 0, move r2 to r1))
> 
> there is no 'else'  branch.

There _is_ an 'else' branch:

if (r3 == 0)
  r1 = r2;
else
  r1 = r1;

With that, the insn definition is easy enough:

(define_insn "*movz"
	[(set (match_operand:SI 0 "register_operand" "=d")
	      (if_then_else (eq (match_operand:SI 1 "register_operand" "d")
				(const_int 0))
			    (match_operand:SI 2 "register_operand" "d")
			    (match_operand:SI 3 "register_operand" "0")))]
	""
	"movz\t%0, %2, %1"
)

This is not all that different from the "*movsicc_noc" pattern in i386.md.
You may want to add a reverse conditional pattern too, i.e. with (ne ...)
instead of (eq ...) and operands 2 and 3 swapped.

As for the expander, I don't know enough of our target machine to write one,
and I'm not sure you need one. Passes such as combine, ce1, ce2 and ce3 may
create "*movz".

Having read the rest of the thread, I suggest you reread the documentation
about define_expand, in particular the description of the DONE and FAIL
macros for the preparation statements and how they affect the generation of
the RTL template.

-- 
Rask Ingemann Lambertsen