e189666a2d
This library captures use of __builtin_popcount and __builtin_ctz on GCC/clang and hopefully handles the MSVC case. Signed-off-by: Keith Rothman <537074+litghost@users.noreply.github.com>
52 lines
1.5 KiB
C++
52 lines
1.5 KiB
C++
/*
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* nextpnr -- Next Generation Place and Route
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*
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* Copyright (c) 2013 Mike Pedersen
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* Copyright (C) 2021 Symbiflow Authors
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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*/
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#include "bits.h"
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#include <limits>
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#include <stdexcept>
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namespace nextpnr {
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int Bits::generic_popcount(unsigned int v) {
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unsigned int c; // c accumulates the total bits set in v
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for (c = 0; v; c++) {
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v &= v - 1; // clear the least significant bit set
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}
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return c;
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}
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int Bits::generic_ctz(unsigned int x) {
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if(x == 0) {
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throw std::runtime_error("Cannot call ctz with arg = 0");
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}
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for(size_t i = 0; i < std::numeric_limits<unsigned int>::digits; ++i) {
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if((x & (1 << i)) != 0) {
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return i;
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}
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}
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// Unreachable!
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throw std::runtime_error("Unreachable!");
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}
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};
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