lib/aarch32/arm32_aeabi_divmod.c

   1 /*
   2  * Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved.
   3  *
   4  * SPDX-License-Identifier: BSD-3-Clause
   5  */
   6
   7 /*
   8  * Form ABI specifications:
   9  *      int __aeabi_idiv(int numerator, int denominator);
  10  *     unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator);
  11  *
  12  *     typedef struct { int quot; int rem; } idiv_return;
  13  *     typedef struct { unsigned quot; unsigned rem; } uidiv_return;
  14  *
  15  *     __value_in_regs idiv_return __aeabi_idivmod(int numerator,
  16  *     int *denominator);
  17  *     __value_in_regs uidiv_return __aeabi_uidivmod(unsigned *numerator,
  18  *     unsigned denominator);
  19  */
  20
  21 /* struct qr - stores quotient/remainder to handle divmod EABI interfaces. */
  22 struct qr {
  23         unsigned int q;         /* computed quotient */
  24         unsigned int r;         /* computed remainder */
  25         unsigned int q_n;       /* specifies if quotient shall be negative */
  26         unsigned int r_n;       /* specifies if remainder shall be negative */
  27 };
  28
  29 static void uint_div_qr(unsigned int numerator, unsigned int denominator,
  30                         struct qr *qr);
  31
  32 /* returns in R0 and R1 by tail calling an asm function */
  33 unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator);
  34
  35 unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator);
  36
  37 /* returns in R0 and R1 by tail calling an asm function */
  38 signed int __aeabi_idivmod(signed int numerator, signed int denominator);
  39
  40 signed int __aeabi_idiv(signed int numerator, signed int denominator);
  41
  42 /*
  43  * __ste_idivmod_ret_t __aeabi_idivmod(signed numerator, signed denominator)
  44  * Numerator and Denominator are received in R0 and R1.
  45  * Where __ste_idivmod_ret_t is returned in R0 and R1.
  46  *
  47  * __ste_uidivmod_ret_t __aeabi_uidivmod(unsigned numerator,
  48  *                                       unsigned denominator)
  49  * Numerator and Denominator are received in R0 and R1.
  50  * Where __ste_uidivmod_ret_t is returned in R0 and R1.
  51  */
  52 #ifdef __GNUC__
  53 signed int ret_idivmod_values(signed int quotient, signed int remainder);
  54 unsigned int ret_uidivmod_values(unsigned int quotient, unsigned int remainder);
  55 #else
  56 #error "Compiler not supported"
  57 #endif
  58
  59 static void division_qr(unsigned int n, unsigned int p, struct qr *qr)
  60 {
  61         unsigned int i = 1, q = 0;
  62
  63         if (p == 0) {
  64                 qr->r = 0xFFFFFFFF;     /* division by 0 */
  65                 return;
  66         }
  67
  68         while ((p >> 31) == 0) {
  69                 i = i << 1;     /* count the max division steps */
  70                 p = p << 1;     /* increase p until it has maximum size*/
  71         }
  72
  73         while (i > 0) {
  74                 q = q << 1;     /* write bit in q at index (size-1) */
  75                 if (n >= p) {
  76                         n -= p;
  77                         q++;
  78                 }
  79                 p = p >> 1;     /* decrease p */
  80                 i = i >> 1;     /* decrease remaining size in q */
  81         }
  82         qr->r = n;
  83         qr->q = q;
  84 }
  85
  86 static void uint_div_qr(unsigned int numerator, unsigned int denominator,
  87                         struct qr *qr)
  88 {
  89         division_qr(numerator, denominator, qr);
  90
  91         /* negate quotient and/or remainder according to requester */
  92         if (qr->q_n)
  93                 qr->q = -qr->q;
  94         if (qr->r_n)
  95                 qr->r = -qr->r;
  96 }
  97
  98 unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator)
  99 {
 100         struct qr qr = { .q_n = 0, .r_n = 0 };
 101
 102         uint_div_qr(numerator, denominator, &qr);
 103
 104         return qr.q;
 105 }
 106
 107 unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator)
 108 {
 109         struct qr qr = { .q_n = 0, .r_n = 0 };
 110
 111         uint_div_qr(numerator, denominator, &qr);
 112
 113         return ret_uidivmod_values(qr.q, qr.r);
 114 }
 115
 116 signed int __aeabi_idiv(signed int numerator, signed int denominator)
 117 {
 118         struct qr qr = { .q_n = 0, .r_n = 0 };
 119
 120         if (((numerator < 0) && (denominator > 0)) ||
 121             ((numerator > 0) && (denominator < 0)))
 122                 qr.q_n = 1;     /* quotient shall be negate */
 123
 124         if (numerator < 0) {
 125                 numerator = -numerator;
 126                 qr.r_n = 1;     /* remainder shall be negate */
 127         }
 128
 129         if (denominator < 0)
 130                 denominator = -denominator;
 131
 132         uint_div_qr(numerator, denominator, &qr);
 133
 134         return qr.q;
 135 }
 136
 137 signed int __aeabi_idivmod(signed int numerator, signed int denominator)
 138 {
 139         struct qr qr = { .q_n = 0, .r_n = 0 };
 140
 141         if (((numerator < 0) && (denominator > 0)) ||
 142             ((numerator > 0) && (denominator < 0)))
 143                 qr.q_n = 1;     /* quotient shall be negate */
 144
 145         if (numerator < 0) {
 146                 numerator = -numerator;
 147                 qr.r_n = 1;     /* remainder shall be negate */
 148         }
 149
 150         if (denominator < 0)
 151                 denominator = -denominator;
 152
 153         uint_div_qr(numerator, denominator, &qr);
 154
 155         return ret_idivmod_values(qr.q, qr.r);
 156 }