inlines.h

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/**
 *  Copyright (C) 2026 HJimmyK(Jericho Knox)
 *
 *  This file is part of LAMMP.
 *
 *  LAMMP is free software: you can redistribute it and/or modify it under
 *  the terms of the GNU Lesser General Public License (LGPL) as published
 *   by the Free Software Foundation; either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed WITHOUT ANY WARRANTY.
 *
 *  See <https://www.gnu.org/licenses/>.
 */
 
#ifndef __LAMMP_INLINES_H__
#define __LAMMP_INLINES_H__
 
#include "../lmmpn.h"
#include "mparam.h"
 
#ifdef _MSC_VER
#include <intrin.h>
#endif
 
static inline int __lmmp_limb_bits_(mp_limb_t x) {
    int k = 0;
    while (x) {
        x >>= 1;
        k++;
    }
    return k;
}
 
static inline int __lmmp_limb_popcnt_(mp_limb_t x) {
#if defined(__GNUC__) || defined(__clang__)
    mp_limb_t count;
#if defined(__x86_64__) && defined(USE_ASM)
    __asm__ volatile("popcnt %1, %0" : "=r"(count) : "r"(x) : "cc");
#else
    count = __builtin_popcountll(x);
#endif
    return count;
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
    return (int)__popcnt64(x);
#else
    int k = 0;
    while (x) {
        k += x & 1;
        x >>= 1;
    }
    return k;
#endif
}
 
static inline int __lmmp_leading_zeros_(mp_limb_t x) {
    if (x == 0) return 64;
#ifdef __GNUC__
    return __builtin_clzll(x);
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
    unsigned long index;
    _BitScanReverse64(&index, x);  
    return 63 - (int)index;
#else
    int n = 0;
    if (x <= 0x00000000FFFFFFFF) { n += 32; x <<= 32; }
    if (x <= 0x0000FFFFFFFFFFFF) { n += 16; x <<= 16; }
    if (x <= 0x00FFFFFFFFFFFFFF) { n += 8;  x <<= 8; }
    if (x <= 0x0FFFFFFFFFFFFFFF) { n += 4;  x <<= 4; }
    if (x <= 0x3FFFFFFFFFFFFFFF) { n += 2;  x <<= 2; }
    if (x <= 0x7FFFFFFFFFFFFFFF) { n += 1;  x <<= 1; }
    return n;
#endif
}
 
static inline int __lmmp_tailing_zeros_(mp_limb_t x) {
    if (x == 0) return 64;
#ifdef __GNUC__
    return __builtin_ctzll(x);
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
    unsigned long index;
    _BitScanForward64(&index, x);
    return (int)index;
#else
    int n = 0;
    if ((x & 0x00000000FFFFFFFF) == 0) { n += 32; x >>= 32; }
    if ((x & 0x000000000000FFFF) == 0) { n += 16; x >>= 16; }
    if ((x & 0x00000000000000FF) == 0) { n += 8;  x >>= 8; }
    if ((x & 0x000000000000000F) == 0) { n += 4;  x >>= 4; }
    if ((x & 0x0000000000000003) == 0) { n += 2;  x >>= 2; }
    if ((x & 0x0000000000000001) == 0) { n += 1;  x >>= 1; }
    return n;
#endif
}
 
static inline void __lmmp_mullh_(mp_limb_t a, mp_limb_t b, mp_ptr restrict dst) {
#if (defined(__GNUC__) || defined(__clang__)) && defined(__SIZEOF_INT128__)
    __uint128_t prod = (__uint128_t)a * b;
    dst[0] = (mp_limb_t)prod;
    dst[1] = (mp_limb_t)(prod >> 64);
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
    dst[0] = _umul128(a, b, dst + 1);
#else
    uint64_t ah = a >> 32, bh = b >> 32;
    a = (uint32_t)a, b = (uint32_t)b;
    uint64_t r0 = a * b, r1 = a * bh, r2 = ah * b, r3 = ah * bh;
    r3 += (r1 >> 32) + (r2 >> 32);
    r1 = (uint32_t)r1, r2 = (uint32_t)r2;
    r1 += r2;
    r1 += (r0 >> 32);
    dst[1] = r3 + (r1 >> 32);
    dst[0] = (r1 << 32) | (uint32_t)r0;
#endif
}
 
static inline mp_limb_t __lmmp_mulh_(mp_limb_t a, mp_limb_t b) {
#if (defined(__GNUC__) || defined(__clang__)) && defined(__SIZEOF_INT128__)
    __uint128_t t = (__uint128_t)a * (__uint128_t)b;
    return (mp_limb_t)(t >> 64);
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
    return __umulh(a, b);
#else
    uint64_t ah = a >> 32, bh = b >> 32;
    a = (uint32_t)a, b = (uint32_t)b;
    uint64_t r0 = a * b, r1 = a * bh, r2 = ah * b, r3 = ah * bh;
    r3 += (r1 >> 32) + (r2 >> 32);
    r1 = (uint32_t)r1, r2 = (uint32_t)r2;
    r1 += r2;
    r1 += (r0 >> 32);
    return r3 + (r1 >> 32);
#endif
}
 
static inline void __lmmp_mul_n_(mp_ptr restrict dst, mp_srcptr restrict numa, mp_srcptr restrict numb, mp_size_t n) {
    if (n < MUL_TOOM22_THRESHOLD)
        lmmp_mul_basecase_(dst, numa, n, numb, n);
    else if (n < MUL_TOOM33_THRESHOLD)
        lmmp_mul_toom22_(dst, numa, n, numb, n);
    else if (n < MUL_TOOM44_THRESHOLD)
        lmmp_mul_toom33_(dst, numa, n, numb, n);
    else if (n < MUL_FFT_THRESHOLD)
        lmmp_mul_toom44_(dst, numa, n, numb, n);
    else
        lmmp_mul_fft_(dst, numa, n, numb, n);
}
 
static inline void __lmmp_sqr_(mp_ptr restrict dst, mp_srcptr restrict numa, mp_size_t na) {
    if (na < MUL_TOOM22_THRESHOLD)
        lmmp_sqr_basecase_(dst, numa, na);
    else if (na < MUL_TOOM33_THRESHOLD)
        lmmp_sqr_toom2_(dst, numa, na);
    else if (na < MUL_TOOM44_THRESHOLD)
        lmmp_sqr_toom3_(dst, numa, na);
    else if (na < MUL_FFT_THRESHOLD)
        lmmp_sqr_toom4_(dst, numa, na);
    else
        lmmp_mul_fft_(dst, numa, na, numa, na);
}
 
#define lmmp_leading_zeros_ __lmmp_leading_zeros_
#define lmmp_tailing_zeros_ __lmmp_tailing_zeros_
#define lmmp_limb_bits_ __lmmp_limb_bits_
#define lmmp_limb_popcnt_ __lmmp_limb_popcnt_
#define lmmp_mullh_ __lmmp_mullh_
#define lmmp_mulh_ __lmmp_mulh_
#define lmmp_sqr_ __lmmp_sqr_
#define lmmp_mul_n_ __lmmp_mul_n_
 
#endif // __LAMMP_INLINES_H__