[RFA:] Fix lsb? bug with insn fields beyond base insn size.

[Doug Evans <dje@transmeta.com>]

Hans-Peter Nilsson writes:
 > Ok to commit?
 > 
 > 2002-06-19  Hans-Peter Nilsson  <hp@axis.com>
 > 
 > 	* types.scm (bitrange-overlap?): Handle lsb0?.
 > 	* utils-gen.scm (-gen-extract-word): Ditto.
 > 
 > Index: utils-gen.scm
 > ===================================================================
 > RCS file: /cvs/src/src/cgen/utils-gen.scm,v
 > retrieving revision 1.6
 > diff -p -c -r1.6 utils-gen.scm
 > *** utils-gen.scm	14 Nov 2001 19:46:43 -0000	1.6
 > --- utils-gen.scm	19 Jun 2002 00:10:20 -0000
 > ***************
 > *** 116,125 ****
 >   
 >   (define (-gen-extract-word word-name word-start word-length start length
 >   			   unsigned? lsb0?)
 > !   ; ??? lsb0?
 > !   (let ((word-end (+ word-start word-length))
 > ! 	(end (+ start length))
 > ! 	(base (if (< start word-start) word-start start)))
 >       (string-append "("
 >   		   "EXTRACT_"
 >   		   (if (current-arch-insn-lsb0?) "LSB0" "MSB0")
 > --- 116,131 ----
 >   
 >   (define (-gen-extract-word word-name word-start word-length start length
 >   			   unsigned? lsb0?)
 > !   ; Canonicalize on the low and high numbered ends of the field; use the
 > !   ; lsb?-adjusted numbering only when necessary.
 > !   (let* ((field-low (if lsb0? (- start length) start))
 > ! 	 (field-high (if lsb0? start (+ start length)))
 > ! 	 (word-low word-start)
 > ! 	 (word-high (+ word-start word-length))
 > ! 	 ; The field part within the extracted word.
 > ! 	 (fieldpart-low (if (< field-low word-low) 0 (- field-low word-low)))
 > ! 	 (fieldpart-high (if (> field-high word-high)
 > ! 			     word-length (- field-high word-low))))
 >       (string-append "("
 >   		   "EXTRACT_"
 >   		   (if (current-arch-insn-lsb0?) "LSB0" "MSB0")
 > ***************
 > *** 133,148 ****
 >   		   ", "
 >   		   (number->string word-length)
 >   		   ", "
 > ! 		   (number->string (if (< start word-start)
 > ! 				       0
 > ! 				       (- start word-start)))
 >   		   ", "
 > ! 		   (number->string (if (< end word-end)
 > ! 				       (- end base)
 > ! 				       (- word-end base)))
 >   		   ") << "
 > ! 		   (number->string (if (> end word-end)
 > ! 				       (- end word-end)
 >   				       0))
 >   		   ")"))
 >   )
 > --- 139,150 ----
 >   		   ", "
 >   		   (number->string word-length)
 >   		   ", "
 > ! 		   (number->string (if lsb0? fieldpart-high fieldpart-low))
 >   		   ", "
 > ! 	>>>>>>>	   (number->string (+ 1 (- fieldpart-high fieldpart-low)))
 >   		   ") << "
 > ! 		   (number->string (if (> field-high word-high)
 > ! 				       (- field-high word-high)
 >   				       0))
 >   		   ")"))
 >   )

Are you sure you want the +1 here (grep for >>>)?
I didn't study the lsb0? = #t case, but for lsb0? = #f I compared the old/new
equations on paper and you don't want the +1.

I'm guessing the same would be true for lsb0? = #t.
[unless of course you rework the fieldpart high/low calculations]