diff options
Diffstat (limited to 'lib/aarch32/arm32_aeabi_divmod.c')
| -rw-r--r-- | lib/aarch32/arm32_aeabi_divmod.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/lib/aarch32/arm32_aeabi_divmod.c b/lib/aarch32/arm32_aeabi_divmod.c new file mode 100644 index 0000000..89a9033 --- /dev/null +++ b/lib/aarch32/arm32_aeabi_divmod.c @@ -0,0 +1,156 @@ +/* + * Copyright (c) 2017-2019, Arm Limited and Contributors. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + */ + +/* + * Form ABI specifications: + * int __aeabi_idiv(int numerator, int denominator); + * unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator); + * + * typedef struct { int quot; int rem; } idiv_return; + * typedef struct { unsigned quot; unsigned rem; } uidiv_return; + * + * __value_in_regs idiv_return __aeabi_idivmod(int numerator, + * int *denominator); + * __value_in_regs uidiv_return __aeabi_uidivmod(unsigned *numerator, + * unsigned denominator); + */ + +/* struct qr - stores quotient/remainder to handle divmod EABI interfaces. */ +struct qr { + unsigned int q; /* computed quotient */ + unsigned int r; /* computed remainder */ + unsigned int q_n; /* specifies if quotient shall be negative */ + unsigned int r_n; /* specifies if remainder shall be negative */ +}; + +static void uint_div_qr(unsigned int numerator, unsigned int denominator, + struct qr *qr); + +/* returns in R0 and R1 by tail calling an asm function */ +unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator); + +unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator); + +/* returns in R0 and R1 by tail calling an asm function */ +signed int __aeabi_idivmod(signed int numerator, signed int denominator); + +signed int __aeabi_idiv(signed int numerator, signed int denominator); + +/* + * __ste_idivmod_ret_t __aeabi_idivmod(signed numerator, signed denominator) + * Numerator and Denominator are received in R0 and R1. + * Where __ste_idivmod_ret_t is returned in R0 and R1. + * + * __ste_uidivmod_ret_t __aeabi_uidivmod(unsigned numerator, + * unsigned denominator) + * Numerator and Denominator are received in R0 and R1. + * Where __ste_uidivmod_ret_t is returned in R0 and R1. + */ +#ifdef __GNUC__ +signed int ret_idivmod_values(signed int quotient, signed int remainder); +unsigned int ret_uidivmod_values(unsigned int quotient, unsigned int remainder); +#else +#error "Compiler not supported" +#endif + +static void division_qr(unsigned int n, unsigned int p, struct qr *qr) +{ + unsigned int i = 1, q = 0; + + if (p == 0) { + qr->r = 0xFFFFFFFF; /* division by 0 */ + return; + } + + while ((p >> 31) == 0) { + i = i << 1; /* count the max division steps */ + p = p << 1; /* increase p until it has maximum size*/ + } + + while (i > 0) { + q = q << 1; /* write bit in q at index (size-1) */ + if (n >= p) { + n -= p; + q++; + } + p = p >> 1; /* decrease p */ + i = i >> 1; /* decrease remaining size in q */ + } + qr->r = n; + qr->q = q; +} + +static void uint_div_qr(unsigned int numerator, unsigned int denominator, + struct qr *qr) +{ + division_qr(numerator, denominator, qr); + + /* negate quotient and/or remainder according to requester */ + if (qr->q_n) + qr->q = -qr->q; + if (qr->r_n) + qr->r = -qr->r; +} + +unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + uint_div_qr(numerator, denominator, &qr); + + return qr.q; +} + +unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + uint_div_qr(numerator, denominator, &qr); + + return ret_uidivmod_values(qr.q, qr.r); +} + +signed int __aeabi_idiv(signed int numerator, signed int denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + if (((numerator < 0) && (denominator > 0)) || + ((numerator > 0) && (denominator < 0))) + qr.q_n = 1; /* quotient shall be negate */ + + if (numerator < 0) { + numerator = -numerator; + qr.r_n = 1; /* remainder shall be negate */ + } + + if (denominator < 0) + denominator = -denominator; + + uint_div_qr(numerator, denominator, &qr); + + return qr.q; +} + +signed int __aeabi_idivmod(signed int numerator, signed int denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + if (((numerator < 0) && (denominator > 0)) || + ((numerator > 0) && (denominator < 0))) + qr.q_n = 1; /* quotient shall be negate */ + + if (numerator < 0) { + numerator = -numerator; + qr.r_n = 1; /* remainder shall be negate */ + } + + if (denominator < 0) + denominator = -denominator; + + uint_div_qr(numerator, denominator, &qr); + + return ret_idivmod_values(qr.q, qr.r); +} |