alignment.lisp

   1 ;;;;------------------------------------------------------------------
   2 ;;;;
   3 ;;;;    Copyright (C) 2001-2002, 2004,
   4 ;;;;    Department of Computer Science, University of Tromso, Norway.
   5 ;;;;
   6 ;;;;    For distribution policy, see the accompanying file COPYING.
   7 ;;;;
   8 ;;;; Filename:      alignment.lisp
   9 ;;;; Description:
  10 ;;;; Author:        Frode Vatvedt Fjeld <frodef@acm.org>
  11 ;;;; Created at:    Wed Apr 10 12:47:08 2002
  12 ;;;;
  13 ;;;; $Id: alignment.lisp,v 1.3 2004/02/10 00:03:09 ffjeld Exp $
  14 ;;;;
  15 ;;;;------------------------------------------------------------------
  16
  17 (in-package #:ia-x86)
  18
  19 (defclass alignment ()
  20   ((type
  21     :initarg :type
  22     :reader alignment-type)))
  23
  24 (defmethod create-alignment ((alignment alignment) pc)
  25   (ecase (first (alignment-type alignment))
  26     (:code
  27      ;; For optimal performance across the Intel Architecture family, it is recommended that:
  28      ;; *  Loop entry labels should be 16-byte aligned when less than eight bytes away from a
  29      ;;    16-byte boundary.
  30      ;; *  Labels that follow a conditional branch should not be aligned.
  31      ;; *  Labels that follow an unconditional branch or function call should be 16-byte aligned
  32      ;;    when less than eight bytes away from a 16-byte boundary.
  33      (ecase (second (alignment-type alignment))
  34        (:loop
  35          (when (< 8 (mod pc 16))
  36            (nthcdr (mod pc 16) '#.(make-list 16 :initial-element #c(#x90 1))))
  37          )))))
  38
  39