#| -*-Scheme-*-

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
    2017, 2018, 2019, 2020 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

MIT/GNU Scheme is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Intel 386 Instruction Set, utilities

(declare (usual-integrations))

;;;; Addressing modes

;; r/m part of ModR/M byte and SIB byte.
;; These are valid only for 32-bit addressing.

(define-ea-database
  ((R (? r))
   (REGISTER)
   #b11 r)

  ((@R (? r indirect-reg))
   (MEMORY)
   #b00 r)

  ((@R 5)				; EBP
   (MEMORY)
   #b01 5
   (BYTE (8 0)))

  ((@R 4)				; ESP
   (MEMORY)
   #b00 4
   (BYTE (3 4)
	 (3 4)
	 (2 0)))

  ((@RO B (? r index-reg) (? offset))
   (MEMORY)
   #b01 r
   (BYTE (8 offset SIGNED)))

  ((@RO UB (? r index-reg) (? offset))
   (MEMORY)
   #b01 r
   (BYTE (8 offset UNSIGNED)))

  ((@RO B 4 (? offset))
   (MEMORY)
   #b01 4
   (BYTE (3 4)
	 (3 4)
	 (2 0)
	 (8 offset SIGNED)))

  ((@RO UB 4 (? offset))
   (MEMORY)
   #b01 4
   (BYTE (3 4)
	 (3 4)
	 (2 0)
	 (8 offset UNSIGNED)))

  ((@RO W (? r index-reg) (? offset))
   (MEMORY)
   #b10 r
   (IMMEDIATE offset ADDRESS SIGNED))

  ((@RO UW (? r index-reg) (? offset))
   (MEMORY)
   #b10 r
   (IMMEDIATE offset ADDRESS UNSIGNED))

  ((@RO W 4 (? offset))			; ESP
   (MEMORY)
   #b10 #b100
   (BYTE (3 4)
	 (3 4)
	 (2 0))
   (IMMEDIATE offset ADDRESS SIGNED))

  ((@RO UW 4 (? offset))		; ESP
   (MEMORY)
   #b10 #b100
   (BYTE (3 4)
	 (3 4)
	 (2 0))
   (IMMEDIATE offset ADDRESS UNSIGNED))
   
  ((@RI (? b base-reg) (? i index-reg) (? s index-scale))
   (MEMORY)
   #b00 #b100
   (BYTE (3 b)
	 (3 i)
	 (2 s)))

  ((@RI 5 (? i index-reg) (? s index-scale)) ; EBP
   (MEMORY)
   #b01 #b100
   (BYTE (3 5)
	 (3 i)
	 (2 s)
	 (8 0)))

  ((@ROI B (? b) (? offset) (? i index-reg) (? s index-scale))
   (MEMORY)
   #b01 #b100
   (BYTE (3 b)
	 (3 i)
	 (2 s)
	 (8 offset SIGNED)))

  ((@ROI UB (? b) (? offset) (? i index-reg) (? s index-scale))
   (MEMORY)
   #b01 #b100
   (BYTE (3 b)
	 (3 i)
	 (2 s)
	 (8 offset UNSIGNED)))

  ((@ROI W (? b) (? offset) (? i index-reg) (? s index-scale))
   (MEMORY)
   #b10 #b100
   (BYTE (3 b)
	 (3 i)
	 (2 s))
   (IMMEDIATE offset ADDRESS SIGNED))

  ((@ROI UW (? b) (? offset) (? i index-reg) (? s index-scale))
   (MEMORY)
   #b10 #b100
   (BYTE (3 b)
	 (3 i)
	 (2 s))
   (IMMEDIATE offset ADDRESS UNSIGNED))

  ((@ (? value))
   (MEMORY)
   #b00 #b101
   (IMMEDIATE value ADDRESS)))

(define-ea-transformer r/mW)
(define-ea-transformer mW MEMORY)
(define-ea-transformer r/mB)
(define-ea-transformer mB MEMORY)

(define-structure (effective-address
		   (conc-name ea/)
		   (constructor make-effective-address))
  (keyword false read-only true)
  (categories false read-only true)
  (mode false read-only true)
  (register false read-only true)
  (extra '() read-only true))

(define (sign-extended-byte value)
  (and (fits-in-signed-byte? value)
       value))

(define (zero-extended-byte value)
  (and (fits-in-unsigned-byte? value)
       value))

(define-integrable (indirect-reg r)
  (and (not (= r esp))
       (not (= r ebp))
       r))

(define-integrable (base-reg r)
  (and (not (= r ebp))
       r))

(define-integrable (index-reg r)
  (and (not (= r esp))
       r))

(define (index-scale scale-value)
  (case scale-value
    ((1) #b00)
    ((2) #b01)
    ((4) #b10)
    ((8) #b11)
    (else false)))