src/compiler/x86/pred.lisp

   1 ;;;; predicate VOPs for the x86 VM
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!VM")
  13 \f
  14 ;;;; the branch VOP
  15
  16 ;;; The unconditional branch, emitted when we can't drop through to the desired
  17 ;;; destination. Dest is the continuation we transfer control to.
  18 (define-vop (branch)
  19   (:info dest)
  20   (:generator 5
  21     (inst jmp dest)))
  22
  23 \f
  24 ;;;; conditional VOPs
  25
  26 ;;; Note: a constant-tn is allowed in CMP; it uses an EA displacement,
  27 ;;; not immediate data.
  28 (define-vop (if-eq)
  29   (:args (x :scs (any-reg descriptor-reg control-stack constant)
  30             :load-if (not (and (sc-is x immediate)
  31                                (sc-is y any-reg descriptor-reg
  32                                       control-stack constant))))
  33          (y :scs (any-reg descriptor-reg immediate)
  34             :load-if (not (and (sc-is x any-reg descriptor-reg immediate)
  35                                (sc-is y control-stack constant)))))
  36   (:conditional)
  37   (:info target not-p)
  38   (:policy :fast-safe)
  39   (:translate eq)
  40   (:generator 3
  41     (cond
  42      ((sc-is y immediate)
  43       (let ((val (tn-value y)))
  44         (etypecase val
  45           (integer
  46            (if (and (zerop val) (sc-is x any-reg descriptor-reg))
  47                (inst test x x) ; smaller
  48              (inst cmp x (fixnumize val))))
  49           (symbol
  50            (inst cmp x (+ nil-value (static-symbol-offset val))))
  51           (character
  52            (inst cmp x (logior (ash (char-code val) n-widetag-bits)
  53                                base-char-widetag))))))
  54      ((sc-is x immediate) ; and y not immediate
  55       ;; Swap the order to fit the compare instruction.
  56       (let ((val (tn-value x)))
  57         (etypecase val
  58           (integer
  59            (if (and (zerop val) (sc-is y any-reg descriptor-reg))
  60                (inst test y y) ; smaller
  61              (inst cmp y (fixnumize val))))
  62           (symbol
  63            (inst cmp y (+ nil-value (static-symbol-offset val))))
  64           (character
  65            (inst cmp y (logior (ash (char-code val) n-widetag-bits)
  66                                base-char-widetag))))))
  67       (t
  68        (inst cmp x y)))
  69
  70     (inst jmp (if not-p :ne :e) target)))