Jeff Epler
19000d6e49
(note: this should probably end up squashed) Most MCUs apart from Cortex-M0 with Thumb 1 have an instruction for computing the "high part" of a multiplication (e.g., the upper 32 bits of a 32x32 multiply). When they do, gcc uses this to implement a small and fast overflow check using the __builtin_mul_overflow intrinsic, which is preferable to the guard division method used in smallint.c. However, in contrast to the previous mp_small_int_mul_overflow routine, which checks that the result fits not only within mp_int_t but is SMALL_INT_FITS(), __builtin_mul_overflow only checks for overflow of the C type. As a result, a slight change in the code flow is needed for MP_BINARY_OP_MULTIPLY. Other sites using mp_small_int_mul_overflow already had the result value flow through to a SMALL_INT_FITS check so they didn't need any additional changes. Signed-off-by: Jeff Epler <jepler@gmail.com>
74 lines
3.2 KiB
C
74 lines
3.2 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2013, 2014 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef MICROPY_INCLUDED_PY_SMALLINT_H
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#define MICROPY_INCLUDED_PY_SMALLINT_H
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#include "py/mpconfig.h"
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#include "py/misc.h"
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// Functions for small integer arithmetic
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#ifndef MP_SMALL_INT_MIN
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// In SMALL_INT, next-to-highest bits is used as sign, so both must match for value in range
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#if MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_A || MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_C
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#define MP_SMALL_INT_MIN ((mp_int_t)(((mp_int_t)MP_OBJ_WORD_MSBIT_HIGH) >> 1))
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#define MP_SMALL_INT_FITS(n) ((((n) ^ ((mp_uint_t)(n) << 1)) & MP_OBJ_WORD_MSBIT_HIGH) == 0)
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// Mask to truncate mp_int_t to positive value
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#define MP_SMALL_INT_POSITIVE_MASK ~(MP_OBJ_WORD_MSBIT_HIGH | (MP_OBJ_WORD_MSBIT_HIGH >> 1))
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#elif MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_B
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#define MP_SMALL_INT_MIN ((mp_int_t)(((mp_int_t)MP_OBJ_WORD_MSBIT_HIGH) >> 2))
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#define MP_SMALL_INT_FITS(n) ((((n) & MP_SMALL_INT_MIN) == 0) || (((n) & MP_SMALL_INT_MIN) == MP_SMALL_INT_MIN))
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// Mask to truncate mp_int_t to positive value
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#define MP_SMALL_INT_POSITIVE_MASK ~(MP_OBJ_WORD_MSBIT_HIGH | (MP_OBJ_WORD_MSBIT_HIGH >> 1) | (MP_OBJ_WORD_MSBIT_HIGH >> 2))
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#elif MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
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#define MP_SMALL_INT_MIN ((mp_int_t)(((mp_int_t)0xffff800000000000) >> 1))
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#define MP_SMALL_INT_FITS(n) ((((n) ^ ((n) << 1)) & 0xffff800000000000) == 0)
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// Mask to truncate mp_int_t to positive value
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#define MP_SMALL_INT_POSITIVE_MASK ~(0xffff800000000000 | (0xffff800000000000 >> 1))
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#endif
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#endif
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#define MP_SMALL_INT_MAX ((mp_int_t)(~(MP_SMALL_INT_MIN)))
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// https://stackoverflow.com/a/4589384/1976323
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// Number of bits in inttype_MAX, or in any (1<<k)-1 where 0 <= k < 2040
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#define MP_IMAX_BITS(m) ((m) / ((m) % 255 + 1) / 255 % 255 * 8 + 7 - 86 / ((m) % 255 + 12))
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// The number of bits in a MP_SMALL_INT including the sign bit.
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#define MP_SMALL_INT_BITS (MP_IMAX_BITS(MP_SMALL_INT_MAX) + 1)
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mp_int_t mp_small_int_modulo(mp_int_t dividend, mp_int_t divisor);
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mp_int_t mp_small_int_floor_divide(mp_int_t num, mp_int_t denom);
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#endif // MICROPY_INCLUDED_PY_SMALLINT_H
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