LXR linux/arch/mn10300/include/asm/div64.h

   1/* MN10300 64-bit division
   2 *
   3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11#ifndef _ASM_DIV64
  12#define _ASM_DIV64
  13
  14#include <linux/types.h>
  15
  16extern void ____unhandled_size_in_do_div___(void);
  17
  18/*
  19 * Beginning with gcc 4.6, the MDR register is represented explicitly.  We
  20 * must, therefore, at least explicitly clobber the register when we make
  21 * changes to it.  The following assembly fragments *could* be rearranged in
  22 * order to leave the moves to/from the MDR register to the compiler, but the
  23 * gains would be minimal at best.
  24 */
  25#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
  26# define CLOBBER_MDR_CC         "mdr", "cc"
  27#else
  28# define CLOBBER_MDR_CC         "cc"
  29#endif
  30
  31/*
  32 * divide n by base, leaving the result in n and returning the remainder
  33 * - we can do this quite efficiently on the MN10300 by cascading the divides
  34 *   through the MDR register
  35 */
  36#define do_div(n, base)                                                 \
  37({                                                                      \
  38        unsigned __rem = 0;                                             \
  39        if (sizeof(n) <= 4) {                                           \
  40                asm("mov        %1,mdr  \n"                             \
  41                    "divu       %2,%0   \n"                             \
  42                    "mov        mdr,%1  \n"                             \
  43                    : "+r"(n), "=d"(__rem)                              \
  44                    : "r"(base), "1"(__rem)                             \
  45                    : CLOBBER_MDR_CC                                    \
  46                    );                                                  \
  47        } else if (sizeof(n) <= 8) {                                    \
  48                union {                                                 \
  49                        unsigned long long l;                           \
  50                        u32 w[2];                                       \
  51                } __quot;                                               \
  52                __quot.l = n;                                           \
  53                asm("mov        %0,mdr  \n"     /* MDR = 0 */           \
  54                    "divu       %3,%1   \n"                             \
  55                    /* __quot.MSL = __div.MSL / base, */                \
  56                    /* MDR = MDR:__div.MSL % base */                    \
  57                    "divu       %3,%2   \n"                             \
  58                    /* __quot.LSL = MDR:__div.LSL / base, */            \
  59                    /* MDR = MDR:__div.LSL % base */                    \
  60                    "mov        mdr,%0  \n"                             \
  61                    : "=d"(__rem), "=r"(__quot.w[1]), "=r"(__quot.w[0]) \
  62                    : "r"(base), "0"(__rem), "1"(__quot.w[1]),          \
  63                      "2"(__quot.w[0])                                  \
  64                    : CLOBBER_MDR_CC                                    \
  65                    );                                                  \
  66                n = __quot.l;                                           \
  67        } else {                                                        \
  68                ____unhandled_size_in_do_div___();                      \
  69        }                                                               \
  70        __rem;                                                          \
  71})
  72
  73/*
  74 * do an unsigned 32-bit multiply and divide with intermediate 64-bit product
  75 * so as not to lose accuracy
  76 * - we use the MDR register to hold the MSW of the product
  77 */
  78static inline __attribute__((const))
  79unsigned __muldiv64u(unsigned val, unsigned mult, unsigned div)
  80{
  81        unsigned result;
  82
  83        asm("mulu       %2,%0   \n"     /* MDR:val = val*mult */
  84            "divu       %3,%0   \n"     /* val = MDR:val/div;
  85                                         * MDR = MDR:val%div */
  86            : "=r"(result)
  87            : "0"(val), "ir"(mult), "r"(div)
  88            : CLOBBER_MDR_CC
  89            );
  90
  91        return result;
  92}
  93
  94/*
  95 * do a signed 32-bit multiply and divide with intermediate 64-bit product so
  96 * as not to lose accuracy
  97 * - we use the MDR register to hold the MSW of the product
  98 */
  99static inline __attribute__((const))
 100signed __muldiv64s(signed val, signed mult, signed div)
 101{
 102        signed result;
 103
 104        asm("mul        %2,%0   \n"     /* MDR:val = val*mult */
 105            "div        %3,%0   \n"     /* val = MDR:val/div;
 106                                         * MDR = MDR:val%div */
 107            : "=r"(result)
 108            : "0"(val), "ir"(mult), "r"(div)
 109            : CLOBBER_MDR_CC
 110            );
 111
 112        return result;
 113}
 114
 115#endif /* _ASM_DIV64 */
 116