md description for intruction that modifies multiple operands

[Richard Earnshaw]

> 
> > That didn't seem to work.  I also tried something like:
> > 
> > 	(define_insn "block4"
> > 	  [(set (match_operand:SI 0 "register_operand" "+d")
> > 	        (unspec:SI [(match_operand:SI 1 "register_operand" "+d")
> > 	                    (match_operand:SI 2 "register_operand" "+d")
> > 	                    (match_operand:SI 3 "register_operand" "+d")] 123))
> > 	   (set (match_dup 1) (unspec:SI [(match_dup 0) (match_dup 2) (match_dup 3)] 124))
> > 	   (set (match_dup 2) (unspec:SI [(match_dup 0) (match_dup 1) (match_dup 3)] 125))
> > 	   (set (match_dup 3) (unspec:SI [(match_dup 0) (match_dup 1) (match_dup 2)] 126))]
> > 	  "TARGET_FOO"
> > 	  "block4\\t%0 # %0,%1,%2,%3")
> > 
> > which works a little better, but still seems to have some problems
> > with the compiler recognizing that every operand is both an input and
> > output.
> > 
> > Am I totally off track here?
> 
> I don't think so. Though it looks like you might want to define a single
> unspec number for the pattern and maybe use a parallel? *guesses*
> 

You are probably better off if you only use match_dup to match inputs to 
inputs and outputs to outputs.  Use tied register allocation for inputs to 
outputs.  Ties are best done using adjacent number pairs.  Hence something 
like:

 	(define_insn "block4"
 	  [(set (match_operand:SI 0 "register_operand" "=d")
 	        (unspec:SI [(match_operand:SI 3 "register_operand" "2")
 	                    (match_operand:SI 5 "register_operand" "4")
 	                    (match_operand:SI 7 "register_operand" "6")] 123))
 	   (set (match_operand:SI 2 "register_operand" "=d")
		 (unspec:SI [(match_operand:SI 1 "register_operand" "0")
			     (match_dup 5) (match_dup 7)] 124))
 	   (set (match_operand:SI 4 "register_operand" "=d")
		 (unspec:SI [(match_dup 1) (match_dup 3) (match_dup 7)] 125))
 	   (set (match_operand:SI 6 "register_operand" "=d")
		 (unspec:SI [(match_dup 1) (match_dup 3) (match_dup 7)] 126))]

 	  "TARGET_FOO"
 	  "block4\\t%0 # %0,%2,%4,%6")