diff options
Diffstat (limited to 'lib/libutils/isoc/arch/arm/arm32_aeabi_divmod.c')
| -rw-r--r-- | lib/libutils/isoc/arch/arm/arm32_aeabi_divmod.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/lib/libutils/isoc/arch/arm/arm32_aeabi_divmod.c b/lib/libutils/isoc/arch/arm/arm32_aeabi_divmod.c new file mode 100644 index 0000000..0df1e51 --- /dev/null +++ b/lib/libutils/isoc/arch/arm/arm32_aeabi_divmod.c @@ -0,0 +1,219 @@ +/* + * Copyright (c) 2014, STMicroelectronics International N.V. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/* + * 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 qutient/remainder to handle divmod EABI interfaces. */ +struct qr { + unsigned q; /* computed quotient */ + unsigned r; /* computed remainder */ + unsigned q_n; /* specficies if quotient shall be negative */ + unsigned r_n; /* specficies if remainder shall be negative */ +}; + +static void uint_div_qr(unsigned numerator, unsigned denominator, + struct qr *qr); + +/* returns in R0 and R1 by tail calling an asm function */ +unsigned __aeabi_uidivmod(unsigned numerator, unsigned denominator); + +unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator); +unsigned __aeabi_uimod(unsigned numerator, unsigned denominator); + +/* returns in R0 and R1 by tail calling an asm function */ +signed __aeabi_idivmod(signed numerator, signed denominator); + +signed __aeabi_idiv(signed numerator, signed denominator); +signed __aeabi_imod(signed numerator, signed 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 ret_idivmod_values(signed quotient, signed remainder); +unsigned ret_uidivmod_values(unsigned quotient, unsigned remainder); +#else +#error "Compiler not supported" +#endif + +static void division_qr(unsigned n, unsigned p, struct qr *qr) +{ + unsigned 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 numerator, unsigned 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 __aeabi_uidiv(unsigned numerator, unsigned denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + uint_div_qr(numerator, denominator, &qr); + + return qr.q; +} + +unsigned __aeabi_uimod(unsigned numerator, unsigned denominator) +{ + struct qr qr = { .q_n = 0, .r_n = 0 }; + + uint_div_qr(numerator, denominator, &qr); + + return qr.r; +} + +unsigned __aeabi_uidivmod(unsigned numerator, unsigned 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 __aeabi_idiv(signed numerator, signed 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 __aeabi_imod(signed numerator, signed denominator) +{ + signed s; + signed i; + signed j; + signed h; + + struct qr qr = { .q_n = 0, .r_n = 0 }; + + /* in case modulo of a power of 2 */ + for (i = 0, j = 0, h = 0, s = denominator; (s != 0) || (h > 1); i++) { + if (s & 1) { + j = i; + h++; + } + s = s >> 1; + } + if (h == 1) + return numerator >> j; + + 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.r; +} + +signed __aeabi_idivmod(signed numerator, signed 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); +} |