/*-------------------------------------------------------------------------
 *
 * pg_crc32c_sse42.c
 *	  Compute CRC-32C checksum using Intel SSE 4.2 or AVX-512 instructions.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/port/pg_crc32c_sse42.c
 *
 *-------------------------------------------------------------------------
 */
#include "c.h"

#include <nmmintrin.h>
#ifdef USE_AVX512_CRC32C_WITH_RUNTIME_CHECK
#include <immintrin.h>
#endif

#include "port/pg_crc32c.h"

pg_attribute_no_sanitize_alignment()
pg_attribute_target("sse4.2")
pg_crc32c
pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len)
{
	const unsigned char *p = data;
	const unsigned char *pend = p + len;

	/*
	 * Process eight bytes of data at a time.
	 *
	 * NB: We do unaligned accesses here. The Intel architecture allows that,
	 * and performance testing didn't show any performance gain from aligning
	 * the begin address.
	 */
#ifdef __x86_64__
	while (p + 8 <= pend)
	{
		crc = (uint32) _mm_crc32_u64(crc, *((const uint64 *) p));
		p += 8;
	}

	/* Process remaining full four bytes if any */
	if (p + 4 <= pend)
	{
		crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
		p += 4;
	}
#else

	/*
	 * Process four bytes at a time. (The eight byte instruction is not
	 * available on the 32-bit x86 architecture).
	 */
	while (p + 4 <= pend)
	{
		crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
		p += 4;
	}
#endif							/* __x86_64__ */

	/* Process any remaining bytes one at a time. */
	while (p < pend)
	{
		crc = _mm_crc32_u8(crc, *p);
		p++;
	}

	return crc;
}

#ifdef USE_AVX512_CRC32C_WITH_RUNTIME_CHECK

/*
 * Note: There is no copyright notice in the following generated code.
 *
 * We have modified the output to
 *   - match our function declaration
 *   - match whitespace to our project style
 *   - add a threshold for the alignment stanza
 */

/* Generated by https://github.com/corsix/fast-crc32/ using: */
/* ./generate -i avx512_vpclmulqdq -p crc32c -a v1e */
/* MIT licensed */

#define clmul_lo(a, b) (_mm512_clmulepi64_epi128((a), (b), 0))
#define clmul_hi(a, b) (_mm512_clmulepi64_epi128((a), (b), 17))

pg_attribute_target("vpclmulqdq,avx512vl")
pg_crc32c
pg_comp_crc32c_avx512(pg_crc32c crc, const void *data, size_t len)
{
	/* adjust names to match generated code */
	pg_crc32c	crc0 = crc;
	const char *buf = data;

	/* Align on cacheline boundary. The threshold is somewhat arbitrary. */
	if (unlikely(len > 256))
	{
		for (; len && ((uintptr_t) buf & 7); --len)
			crc0 = _mm_crc32_u8(crc0, *buf++);
		while (((uintptr_t) buf & 56) && len >= 8)
		{
			crc0 = _mm_crc32_u64(crc0, *(const uint64_t *) buf);
			buf += 8;
			len -= 8;
		}
	}

	if (len >= 64)
	{
		const char *end = buf + len;
		const char *limit = buf + len - 64;
		__m128i		z0;

		/* First vector chunk. */
		__m512i		x0 = _mm512_loadu_si512((const void *) buf),
					y0;
		__m512i		k;

		k = _mm512_broadcast_i32x4(_mm_setr_epi32(0x740eef02, 0, 0x9e4addf8, 0));
		x0 = _mm512_xor_si512(_mm512_castsi128_si512(_mm_cvtsi32_si128(crc0)), x0);
		buf += 64;

		/* Main loop. */
		while (buf <= limit)
		{
			y0 = clmul_lo(x0, k), x0 = clmul_hi(x0, k);
			x0 = _mm512_ternarylogic_epi64(x0, y0,
										   _mm512_loadu_si512((const void *) buf),
										   0x96);
			buf += 64;
		}

		/* Reduce 512 bits to 128 bits. */
		k = _mm512_setr_epi32(0x1c291d04, 0, 0xddc0152b, 0,
							  0x3da6d0cb, 0, 0xba4fc28e, 0,
							  0xf20c0dfe, 0, 0x493c7d27, 0,
							  0, 0, 0, 0);
		y0 = clmul_lo(x0, k), k = clmul_hi(x0, k);
		y0 = _mm512_xor_si512(y0, k);
		z0 = _mm_ternarylogic_epi64(_mm512_castsi512_si128(y0),
									_mm512_extracti32x4_epi32(y0, 1),
									_mm512_extracti32x4_epi32(y0, 2),
									0x96);
		z0 = _mm_xor_si128(z0, _mm512_extracti32x4_epi32(x0, 3));

		/* Reduce 128 bits to 32 bits, and multiply by x^32. */
		crc0 = _mm_crc32_u64(0, _mm_extract_epi64(z0, 0));
		crc0 = _mm_crc32_u64(crc0, _mm_extract_epi64(z0, 1));
		len = end - buf;
	}

	return pg_comp_crc32c_sse42(crc0, buf, len);
}

#endif