Couple of newbie questions

[Richard Sandiford <rsandifo@cambridge.redhat.com>]

Hi,

I'm trying to learn CGEN by doing a mini 6502 port (yes, really).
I have a couple of questions...

1)

In a define-pmacro, is there a way of using .sym to create a symbol
name and then look it up as another pmacro?  I want to do something
like:

    (define-pmacro (create-insn MODE)
      (... (.expand foo- MODE) ... (.expand bar- MODE) ...))

where (create-insn immediate) would cause the definitions of
"foo-immediate" and "bar-immediate" to be substituted. I ended up adding
a new command to do this (patch attached in case anyone's interested).
But please tell me if it's already supported in some other way!

2)

What are the requirements for CGEN_INT_INSN_P?  All the 6502
instructions fit into 24 bits, so the macro is defined to be "1".
But cgen_get_insn_value() and cgen_put_insn_value() seem to expect
instructions to be 8, 16 or 32 bits wide.  Is this a common
assumption, or would it be safe to just change those two to
support 24 bits?  Or would it better to change the condition
for setting CGEN_INT_INSN_P?

Thanks,
Richard

-------------

Index: pmacros.scm
===================================================================
RCS file: /cvs/cvsfiles/devo/cgen/pmacros.scm,v
retrieving revision 1.28
diff -c -r1.28 pmacros.scm
*** pmacros.scm	2000/07/27 04:53:32	1.28
--- pmacros.scm	2000/12/20 11:47:04
***************
*** 494,499 ****
--- 494,513 ----
      (apply map (cons transformer (cons arg1 arg-rest))))
  )
  
+ ; .expand
+ 
+ (define -pmacro-expand-command
+   (lambda args
+     (let* ((name (apply -pmacro-sym args))
+ 	   (pmacro (-pmacro-lookup name)))
+       (if (not (-pmacro? pmacro))
+ 	  (-pmacro-error "not a pmacro" name))
+       (let ((transformer (-pmacro-transformer pmacro)))
+ 	(cond ((procedure? transformer)
+ 	       pmacro)
+ 	      (else transformer)))))
+ )
+ 
  ; .apply
  
  (define (-pmacro-apply pmacro arg-list)
***************
*** 546,551 ****
--- 560,568 ----
  		(-pmacro-make '.map '(macro-name arg1 . arg-rest) #f
  			      -pmacro-map
  			      "map a macro over a list of arguments"))
+   (-pmacro-set! '.expand
+ 		(-pmacro-make '.expand 'symbols #f -pmacro-expand-command
+ 			      "the macro corresponding to a synthetic name"))
    (-pmacro-set! '.apply
  		(-pmacro-make '.apply '(macro-name arg-list) #f -pmacro-apply
  			      "apply a macro, taking arguments from a list"))