* ifield.scm (<ifield>, value): Provide default initial value.

	(ifield-encode-mode): Delete
	(ifield-decode-mode): Delete duplicate definition.
	(<derived-ifield>, 'make!): Initialize members encode, decode.

diff --git a/cgen/ChangeLog b/cgen/ChangeLog
index a47880b..ac963d7 100644 (file)
--- a/cgen/ChangeLog
+++ b/cgen/ChangeLog
@@ -1,3 +1,10 @@
+2009-10-14  Doug Evans  <dje@sebabeach.org>
+
+       * ifield.scm (<ifield>, value): Provide default initial value.
+       (ifield-encode-mode): Delete
+       (ifield-decode-mode): Delete duplicate definition.
+       (<derived-ifield>, 'make!): Initialize members encode, decode.
+
 2009-10-05  Dave Korn  <dave.korn.cygwin@googlemail.com>
 
        * sim-model.scm (@cpu@_prepare_run): Use @prefix@, not @cpu@,

diff --git a/cgen/ifield.scm b/cgen/ifield.scm
index cc74434..3b17cea 100644 (file)
--- a/cgen/ifield.scm
+++ b/cgen/ifield.scm
@@ -51,9 +51,9 @@
                ; here and partially in the operand.
                encode decode
 
-               ; Value of field, if there is one.
+               ; Value of field, if there is one, or #f.
                ; Possible types are: integer, <operand>, ???
-               value
+               (value . #f)
                )
              nil)
 )
@@ -78,23 +78,19 @@
 (define (ifld-word-offset f) (bitrange-word-offset (/ifld-bitrange f)))
 (define (ifld-word-length f) (bitrange-word-length (/ifld-bitrange f)))
 
-; Return the mode of the value passed to the encode rtl.
-; This is the mode of the result of the decode rtl.
+; Return the mode of the decoded value of <ifield> F.
+; ??? This is made easy because we require the decode expression to have
+; an explicit mode.
 
-(define (ifld-encode-mode f)
-  (if (ifld-decode f)
-      ; cadr/cadr gets WI in ((value pc) (sra WI ...))
-      ; FIXME: That's wrong for a fully canonical expression like
-      ; ((value pc) (sra () WI ...)).
-      (mode:lookup (cadr (cadr (ifld-decode f))))
-      (ifld-mode f))
+(define (ifld-decode-mode f)
+  (assert (elm-bound? f 'decode))
+  (let ((d (ifld-decode f)))
+    (if d
+       ;; FIXME: Does this work with canonicalized rtl?
+       (mode:lookup (cadr (cadr d)))
+       (ifld-mode f)))
 )
 
-; Return the mode of the value passed to the decode rtl.
-; This is the mode of the field.
-
-(define (ifld-decode-mode f) (ifld-mode f))
-
 ; Return start of ifield.
 
 (method-make!
@@ -1059,6 +1055,8 @@ Define an instruction multi-field, all arguments specified.
    (elm-set! self 'attrs attrs)
    (elm-set! self 'mode UINT)
    (elm-set! self 'bitrange (make <bitrange> 0 0 0 0 #f))
+   (elm-set! self 'encode #f)
+   (elm-set! self 'decode #f)
    (elm-set! self 'owner owner)
    (elm-set! self 'subfields subfields)
    self)
@@ -1161,19 +1159,6 @@ Define an instruction multi-field, all arguments specified.
   (> (ifld-word-offset f) 0)
 )
 
-; Return the mode of the decoded value of <ifield> F.
-; ??? This is made easy because we require the decode expression to have
-; an explicit mode.
-
-(define (ifld-decode-mode f)
-  (if (not (elm-bound? f 'decode))
-      (ifld-mode f)
-      (let ((d (ifld-decode f)))
-       (if d
-           (mode:lookup (cadr (cadr d)))
-           (ifld-mode f))))
-)
-
 ; Return <hardware> object to use to hold value of <ifield> F.
 ; i.e. one of h-uint, h-sint.
 ; NB: Should be defined in terms of `hardware-for-mode'.