cf99fb40c9
Squashed commit of the following:
libs/libxx: Fix some confusing in naming. If the directory is called libxx, then the library must be libxx.a (unless perhaps LIBCXX is selected).
libs/: Fix paths in moved library directories.
libs: Brute force move of libc, libnx, and libxx to libs. Cannot yet build it in that configuration.
102 lines
3.9 KiB
C
102 lines
3.9 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_umul64.c
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*
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* Copyright (C) 2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/lib/math32.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: umul64
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*
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* Description:
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* Multiply two 64-bit values, factor1 and factor2, and return the
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* truncated 64-bit product.
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*
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* Input Parameters:
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* factor1 and factor2 - The values to be multiplied
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* product - The location to return the product of the two values.
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*
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****************************************************************************/
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void umul64(FAR const struct uint64_s *factor1,
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FAR const struct uint64_s *factor2,
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FAR struct uint64_s *product)
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{
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struct uint64_s part1;
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struct uint64_s part2;
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/* factor1 = factor1->ms << 32 + factor1->ls
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* factor2 = factor2->ms << 32 + factor2->ls
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*
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* Full 128-bit product:
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* factor1 * factor2 = (factor1->ms * factor2->ms << 64) +
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* factor1->ls * (factor2->ms << 32) +
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* factor2->ls * (factor1->ms << 32) +
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* factor1->ls * factor2->ls
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*
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* Truncated, 64-bit product:
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* factor1 * factor2 = (factor1->ls * factor2->ms +
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* factor2->ls * factor1->ms) << 32) +
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* factor1->ls * factor2->ls
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*
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* part1 = (factor1->ls * factor2->ms +
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* factor2->ls * factor1->ms) << 32)
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* part2 = factor1->ls * factor2->ls
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* factor1 * factor2 = part1 + part2
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*/
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/* Get part1 = factor1->ls * factor2->ms + factor2->ls * factor1->ms,
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* shifting left by 32-bits (truncating to 64-bits)
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*/
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part1.ms = factor1->ls * factor2->ms +
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factor2->ls * factor2->ms;
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part1.ls = 0;
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/* Get the full 64-bit part2 = factor1->ls * factor2->ls */
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umul32(factor1->ls, factor2->ls, &part2);
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/* The product is then the sum */
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uadd64(&part1, &part2, product);
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}
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