arch/sh/kernel/cpu/sh2a/opcode_helper.c

   1 /*
   2  * arch/sh/kernel/cpu/sh2a/opcode_helper.c
   3  *
   4  * Helper for the SH-2A 32-bit opcodes.
   5  *
   6  *  Copyright (C) 2007  Paul Mundt
   7  *
   8  * This file is subject to the terms and conditions of the GNU General Public
   9  * License.  See the file "COPYING" in the main directory of this archive
  10  * for more details.
  11  */
  12 #include <linux/kernel.h>
  13 #include <asm/system.h>
  14
  15 /*
  16  * Instructions on SH are generally fixed at 16-bits, however, SH-2A
  17  * introduces some 32-bit instructions. Since there are no real
  18  * constraints on their use (and they can be mixed and matched), we need
  19  * to check the instruction encoding to work out if it's a true 32-bit
  20  * instruction or not.
  21  *
  22  * Presently, 32-bit opcodes have only slight variations in what the
  23  * actual encoding looks like in the first-half of the instruction, which
  24  * makes it fairly straightforward to differentiate from the 16-bit ones.
  25  *
  26  * First 16-bits of encoding            Used by
  27  *
  28  *      0011nnnnmmmm0001        mov.b, mov.w, mov.l, fmov.d,
  29  *                              fmov.s, movu.b, movu.w
  30  *
  31  *      0011nnnn0iii1001        bclr.b, bld.b, bset.b, bst.b, band.b,
  32  *                              bandnot.b, bldnot.b, bor.b, bornot.b,
  33  *                              bxor.b
  34  *
  35  *      0000nnnniiii0000        movi20
  36  *      0000nnnniiii0001        movi20s
  37  */
  38 unsigned int instruction_size(unsigned int insn)
  39 {
  40         /* Look for the common cases */
  41         switch ((insn & 0xf00f)) {
  42         case 0x0000:    /* movi20 */
  43         case 0x0001:    /* movi20s */
  44         case 0x3001:    /* 32-bit mov/fmov/movu variants */
  45                 return 4;
  46         }
  47
  48         /* And the special cases.. */
  49         switch ((insn & 0xf08f)) {
  50         case 0x3009:    /* 32-bit b*.b bit operations */
  51                 return 4;
  52         }
  53
  54         return 2;
  55 }