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>
74 lines
2.4 KiB
C++
74 lines
2.4 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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// This is a small library for implementing common bit vector utilities,
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// namely:
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//
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// - popcount : The number of bits set in an unsigned int
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// - ctz : The number of trailing zero bits in an unsigned int.
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// Must be called with a value that has at least 1 bit set.
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//
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// These methods will typically use instrinics when available, and have a
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// generic fallback in the event that the instrinic is not available.
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//
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// If clz (count leading zeros) is needed, it can be added when needed.
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#ifndef BITS_H
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#define BITS_H
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#if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86))
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#include <intrin.h>
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#pragma intrinsic(_BitScanForward,_BitScanReverse,__popcnt)
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#endif
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// Uses plain nextpnr namespace to avoid header inclusion nightmare that is
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// "nextpnr.h".
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namespace nextpnr {
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struct Bits {
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static int generic_popcount(unsigned int x);
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static int generic_ctz(unsigned int x);
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static int popcount(unsigned int x) {
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#if defined(__GNUC__) || defined(__clang__)
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return __builtin_popcount(x);
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#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86))
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return __popcnt(v);
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#else
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return generic_popcount(x);
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#endif
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}
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static int ctz(unsigned int x) {
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#if defined(__GNUC__) || defined(__clang__)
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return __builtin_ctz(x);
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#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86))
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unsigned long result;
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_BitScanForward(&result, v);
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return result;
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#else
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return generic_ctz(x);
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#endif
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}
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};
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};
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#endif /* BITS_H */
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