#define update_asm CRYPTO_SHARED_NAMESPACE(update_asm)
#define _update_asm _CRYPTO_SHARED_NAMESPACE(update_asm)
#define vec_reduce_asm CRYPTO_SHARED_NAMESPACE(vec_reduce_asm)
#define _vec_reduce_asm _CRYPTO_SHARED_NAMESPACE(vec_reduce_asm)
/*
  This file is for the inversion-free Berlekamp-Massey algorithm
  see https://ieeexplore.ieee.org/document/87857

  For the implementation strategy, see
  https://eprint.iacr.org/2017/793.pdf
*/
// 20221231 djb: ALIGN(32) for some arrays; tnx thom wiggers
// 20221230 djb: add linker lines

// linker define bm
// linker use update_asm vec_reduce_asm
// linker use vec128_mul_asm
// linker use vec256_mul_asm
// linker use gf_inv

#include "bm.h"

#include "gf.h"
#include "vec128.h"
#include "params.h"

#include <stdint.h>

extern gf vec_reduce_asm(vec128 *);
extern void update_asm(void *, gf, int);

static inline uint16_t mask_nonzero(gf a)
{
	uint32_t ret = a;

	ret -= 1;
	ret >>= 31;
	ret -= 1;

	return ret;
}

static inline uint16_t mask_leq(uint16_t a, uint16_t b)
{
	uint32_t a_tmp = a;
	uint32_t b_tmp = b;
	uint32_t ret = b_tmp - a_tmp; 

	ret >>= 31;
	ret -= 1;

	return ret;
}

static inline void vec128_cmov(vec128 out[][2], uint16_t mask)
{
	int i;

	vec128 v0, v1;

	vec128 m0 = vec128_set1_16b( mask);
	vec128 m1 = vec128_set1_16b(~mask);

	for (i = 0; i < GFBITS; i++)
	{
		v0 = vec128_and(out[i][1], m0);
		v1 = vec128_and(out[i][0], m1);
		out[i][0] = vec128_or(v0, v1);
	}
}

static inline void interleave(vec256 *in, int idx0, int idx1, vec256 *mask, int b)
{
	int s = 1 << b;

	vec256 x, y;

	x = vec256_or(vec256_and(in[idx0], mask[0]), 
	vec256_sll_4x(vec256_and(in[idx1], mask[0]), s));

	y = vec256_or(vec256_srl_4x(vec256_and(in[idx0], mask[1]), s),
	                            vec256_and(in[idx1], mask[1]));

	in[idx0] = x;
	in[idx1] = y;
}

/* input: in, field elements in bitsliced form */
/* output: out, field elements in non-bitsliced form */
static inline void get_coefs(gf *out, vec256 *in)
{
	int i, k;

	vec256 mask[4][2];
	vec256 buf[16];
	
	for (i =  0; i < 13; i++) buf[i] = in[i];
	for (i = 13; i < 16; i++) buf[i] = vec256_setzero();

	mask[0][0] = vec256_set1_16b(0x5555);
	mask[0][1] = vec256_set1_16b(0xAAAA);
	mask[1][0] = vec256_set1_16b(0x3333);
	mask[1][1] = vec256_set1_16b(0xCCCC);
	mask[2][0] = vec256_set1_16b(0x0F0F);
	mask[2][1] = vec256_set1_16b(0xF0F0);
	mask[3][0] = vec256_set1_16b(0x00FF);
	mask[3][1] = vec256_set1_16b(0xFF00);

	interleave(buf,  0,  8, mask[3], 3);
	interleave(buf,  1,  9, mask[3], 3);
	interleave(buf,  2, 10, mask[3], 3);
	interleave(buf,  3, 11, mask[3], 3);
	interleave(buf,  4, 12, mask[3], 3);
	interleave(buf,  5, 13, mask[3], 3);
	interleave(buf,  6, 14, mask[3], 3);
	interleave(buf,  7, 15, mask[3], 3);

	interleave(buf,  0,  4, mask[2], 2);
	interleave(buf,  1,  5, mask[2], 2);
	interleave(buf,  2,  6, mask[2], 2);
	interleave(buf,  3,  7, mask[2], 2);
	interleave(buf,  8, 12, mask[2], 2);
	interleave(buf,  9, 13, mask[2], 2);
	interleave(buf, 10, 14, mask[2], 2);
	interleave(buf, 11, 15, mask[2], 2);

	interleave(buf,  0,  2, mask[1], 1);
	interleave(buf,  1,  3, mask[1], 1);
	interleave(buf,  4,  6, mask[1], 1);
	interleave(buf,  5,  7, mask[1], 1);
	interleave(buf,  8, 10, mask[1], 1);
	interleave(buf,  9, 11, mask[1], 1);
	interleave(buf, 12, 14, mask[1], 1);
	interleave(buf, 13, 15, mask[1], 1);

	interleave(buf,  0,  1, mask[0], 0);
	interleave(buf,  2,  3, mask[0], 0);
	interleave(buf,  4,  5, mask[0], 0);
	interleave(buf,  6,  7, mask[0], 0);
	interleave(buf,  8,  9, mask[0], 0);
	interleave(buf, 10, 11, mask[0], 0);
	interleave(buf, 12, 13, mask[0], 0);
	interleave(buf, 14, 15, mask[0], 0);

        for (i = 0; i < 16; i++)
        for (k = 0; k <  4; k++) {
                out[ (4*0 + k)*16 + i ] = (vec256_extract(buf[i], 0) >> (k*16)) & GFMASK;
                out[ (4*1 + k)*16 + i ] = (vec256_extract(buf[i], 1) >> (k*16)) & GFMASK;
                out[ (4*2 + k)*16 + i ] = (vec256_extract(buf[i], 2) >> (k*16)) & GFMASK;
                out[ (4*3 + k)*16 + i ] = (vec256_extract(buf[i], 3) >> (k*16)) & GFMASK;
        }
}

/* input: in, sequence of field elements */
/* output: out, minimal polynomial of in */
void bm(vec128 *out, vec256 *in)
{
	int i;
	uint16_t N, L;
	uint16_t mask;
	uint64_t one = 1, t;

	vec128 prod[ GFBITS ];
	vec128 interval[GFBITS];

	ALIGN(32) vec128 db[ GFBITS ][ 2 ];
	ALIGN(32) vec128 BC_tmp[ GFBITS ][ 2 ];
	ALIGN(32) vec128 BC[ GFBITS ][ 2 ];

	gf d, b, c0 = 1;
	gf coefs[256];

	// initialization

	get_coefs(coefs, in);

	BC[0][0] = vec128_set2x(0, one << 63);
	BC[0][1] = vec128_setzero();

	for (i = 1; i < GFBITS; i++)
		BC[i][0] = BC[i][1] = vec128_setzero();

	b = 1;
	L = 0;

	//

	for (i = 0; i < GFBITS; i++)
		interval[i] = vec128_setzero();

	for (N = 0; N < 256; N++)
	{
		vec128_mul_asm(prod, interval, BC[0]+1, 32);
		update_asm(interval, coefs[N], 16);

		d = vec_reduce_asm(prod);

		t = gf_mul2(c0, coefs[N], b);
		d ^= t & 0xFFFFFFFF;

		mask = mask_nonzero(d) & mask_leq(L*2, N);

		for (i = 0; i < GFBITS; i++) 
		{
			db[i][0] = vec128_setbits((d >> i) & 1);
			db[i][1] = vec128_setbits((b >> i) & 1);
		}

		vec256_mul((vec256*) BC_tmp, (vec256*) db, (vec256*) BC);

		vec128_cmov(BC, mask);
		update_asm(BC, c0 & mask, 32);

		for (i = 0; i < GFBITS; i++) 
			BC[i][1] = vec128_xor(BC_tmp[i][0], BC_tmp[i][1]);

		c0 = t >> 32; 
		b = (d & mask) | (b & ~mask);
		L = ((N+1-L) & mask) | (L & ~mask);
	}

	c0 = gf_inv(c0);

	for (i = 0; i < GFBITS; i++) 
		prod[i] = vec128_setbits((c0 >> i) & 1);

	vec128_mul_asm(out, prod, BC[0]+1, 32);
}

