1 // SPDX-License-Identifier: BSD-2-Clause
2 /*
3 * Copyright (c) 2014, STMicroelectronics International N.V.
4 */
5
6 /*
7 * Form ABI specifications:
8 * int __aeabi_idiv(int numerator, int denominator);
9 * unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator);
10 *
11 * typedef struct { int quot; int rem; } idiv_return;
12 * typedef struct { unsigned quot; unsigned rem; } uidiv_return;
13 *
14 * __value_in_regs idiv_return __aeabi_idivmod(int numerator,
15 * int *denominator);
16 * __value_in_regs uidiv_return __aeabi_uidivmod(unsigned *numerator,
17 * unsigned denominator);
18 */
19
20 /* struct qr - stores qutient/remainder to handle divmod EABI interfaces. */
21 struct qr {
22 unsigned q; /* computed quotient */
23 unsigned r; /* computed remainder */
24 unsigned q_n; /* specficies if quotient shall be negative */
25 unsigned r_n; /* specficies if remainder shall be negative */
26 };
27
28 static void uint_div_qr(unsigned numerator, unsigned denominator,
29 struct qr *qr);
30
31 /* returns in R0 and R1 by tail calling an asm function */
32 unsigned __aeabi_uidivmod(unsigned numerator, unsigned denominator);
33
34 unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator);
35
36 /* returns in R0 and R1 by tail calling an asm function */
37 signed __aeabi_idivmod(signed numerator, signed denominator);
38
39 signed __aeabi_idiv(signed numerator, signed denominator);
40
41 /*
42 * __ste_idivmod_ret_t __aeabi_idivmod(signed numerator, signed denominator)
43 * Numerator and Denominator are received in R0 and R1.
44 * Where __ste_idivmod_ret_t is returned in R0 and R1.
45 *
46 * __ste_uidivmod_ret_t __aeabi_uidivmod(unsigned numerator,
47 * unsigned denominator)
48 * Numerator and Denominator are received in R0 and R1.
49 * Where __ste_uidivmod_ret_t is returned in R0 and R1.
50 */
51 #ifdef __GNUC__
52 signed ret_idivmod_values(signed quotient, signed remainder);
53 unsigned ret_uidivmod_values(unsigned quotient, unsigned remainder);
54 #else
55 #error "Compiler not supported"
56 #endif
57
division_qr(unsigned n,unsigned p,struct qr * qr)58 static void division_qr(unsigned n, unsigned p, struct qr *qr)
59 {
60 unsigned i = 1, q = 0;
61 if (p == 0) {
62 qr->r = 0xFFFFFFFF; /* division by 0 */
63 return;
64 }
65
66 while ((p >> 31) == 0) {
67 i = i << 1; /* count the max division steps */
68 p = p << 1; /* increase p until it has maximum size*/
69 }
70
71 while (i > 0) {
72 q = q << 1; /* write bit in q at index (size-1) */
73 if (n >= p)
74 {
75 n -= p;
76 q++;
77 }
78 p = p >> 1; /* decrease p */
79 i = i >> 1; /* decrease remaining size in q */
80 }
81 qr->r = n;
82 qr->q = q;
83 }
84
uint_div_qr(unsigned numerator,unsigned denominator,struct qr * qr)85 static void uint_div_qr(unsigned numerator, unsigned denominator, struct qr *qr)
86 {
87
88 division_qr(numerator, denominator, qr);
89
90 /* negate quotient and/or remainder according to requester */
91 if (qr->q_n)
92 qr->q = -qr->q;
93 if (qr->r_n)
94 qr->r = -qr->r;
95 }
96
__aeabi_uidiv(unsigned numerator,unsigned denominator)97 unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator)
98 {
99 struct qr qr = { .q_n = 0, .r_n = 0 };
100
101 uint_div_qr(numerator, denominator, &qr);
102
103 return qr.q;
104 }
105
__aeabi_uidivmod(unsigned numerator,unsigned denominator)106 unsigned __aeabi_uidivmod(unsigned numerator, unsigned denominator)
107 {
108 struct qr qr = { .q_n = 0, .r_n = 0 };
109
110 uint_div_qr(numerator, denominator, &qr);
111
112 return ret_uidivmod_values(qr.q, qr.r);
113 }
114
__aeabi_idiv(signed numerator,signed denominator)115 signed __aeabi_idiv(signed numerator, signed denominator)
116 {
117 struct qr qr = { .q_n = 0, .r_n = 0 };
118
119 if (((numerator < 0) && (denominator > 0)) ||
120 ((numerator > 0) && (denominator < 0)))
121 qr.q_n = 1; /* quotient shall be negate */
122 if (numerator < 0) {
123 numerator = -numerator;
124 qr.r_n = 1; /* remainder shall be negate */
125 }
126 if (denominator < 0)
127 denominator = -denominator;
128
129 uint_div_qr(numerator, denominator, &qr);
130
131 return qr.q;
132 }
133
__aeabi_idivmod(signed numerator,signed denominator)134 signed __aeabi_idivmod(signed numerator, signed denominator)
135 {
136 struct qr qr = { .q_n = 0, .r_n = 0 };
137
138 if (((numerator < 0) && (denominator > 0)) ||
139 ((numerator > 0) && (denominator < 0)))
140 qr.q_n = 1; /* quotient shall be negate */
141 if (numerator < 0) {
142 numerator = -numerator;
143 qr.r_n = 1; /* remainder shall be negate */
144 }
145 if (denominator < 0)
146 denominator = -denominator;
147
148 uint_div_qr(numerator, denominator, &qr);
149
150 return ret_idivmod_values(qr.q, qr.r);
151 }
152