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
division_qr(unsigned int n,unsigned int p,struct qr * qr)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
uint_div_qr(unsigned int numerator,unsigned int denominator,struct qr * qr)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
__aeabi_uidiv(unsigned int numerator,unsigned int denominator)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
__aeabi_uidivmod(unsigned int numerator,unsigned int denominator)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
__aeabi_idiv(signed int numerator,signed int denominator)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
__aeabi_idivmod(signed int numerator,signed int denominator)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 }
157