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/*
* SPDX-License-Identifier: GPL-2.0-or-later
* buffer_is_zero acceleration, x86 version.
*/
#if defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
#include <immintrin.h>
/* Helper for preventing the compiler from reassociating
chains of binary vector operations. */
#define SSE_REASSOC_BARRIER(vec0, vec1) asm("" : "+x"(vec0), "+x"(vec1))
/* Note that these vectorized functions may assume len >= 256. */
static bool __attribute__((target("sse2")))
buffer_zero_sse2(const void *buf, size_t len)
{
/* Unaligned loads at head/tail. */
__m128i v = *(__m128i_u *)(buf);
__m128i w = *(__m128i_u *)(buf + len - 16);
/* Align head/tail to 16-byte boundaries. */
const __m128i *p = QEMU_ALIGN_PTR_DOWN(buf + 16, 16);
const __m128i *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 16);
__m128i zero = { 0 };
/* Collect a partial block at tail end. */
v |= e[-1]; w |= e[-2];
SSE_REASSOC_BARRIER(v, w);
v |= e[-3]; w |= e[-4];
SSE_REASSOC_BARRIER(v, w);
v |= e[-5]; w |= e[-6];
SSE_REASSOC_BARRIER(v, w);
v |= e[-7]; v |= w;
/*
* Loop over complete 128-byte blocks.
* With the head and tail removed, e - p >= 14, so the loop
* must iterate at least once.
*/
do {
v = _mm_cmpeq_epi8(v, zero);
if (unlikely(_mm_movemask_epi8(v) != 0xFFFF)) {
return false;
}
v = p[0]; w = p[1];
SSE_REASSOC_BARRIER(v, w);
v |= p[2]; w |= p[3];
SSE_REASSOC_BARRIER(v, w);
v |= p[4]; w |= p[5];
SSE_REASSOC_BARRIER(v, w);
v |= p[6]; w |= p[7];
SSE_REASSOC_BARRIER(v, w);
v |= w;
p += 8;
} while (p < e - 7);
return _mm_movemask_epi8(_mm_cmpeq_epi8(v, zero)) == 0xFFFF;
}
#ifdef CONFIG_AVX2_OPT
static bool __attribute__((target("avx2")))
buffer_zero_avx2(const void *buf, size_t len)
{
/* Unaligned loads at head/tail. */
__m256i v = *(__m256i_u *)(buf);
__m256i w = *(__m256i_u *)(buf + len - 32);
/* Align head/tail to 32-byte boundaries. */
const __m256i *p = QEMU_ALIGN_PTR_DOWN(buf + 32, 32);
const __m256i *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 32);
__m256i zero = { 0 };
/* Collect a partial block at tail end. */
v |= e[-1]; w |= e[-2];
SSE_REASSOC_BARRIER(v, w);
v |= e[-3]; w |= e[-4];
SSE_REASSOC_BARRIER(v, w);
v |= e[-5]; w |= e[-6];
SSE_REASSOC_BARRIER(v, w);
v |= e[-7]; v |= w;
/* Loop over complete 256-byte blocks. */
for (; p < e - 7; p += 8) {
/* PTEST is not profitable here. */
v = _mm256_cmpeq_epi8(v, zero);
if (unlikely(_mm256_movemask_epi8(v) != 0xFFFFFFFF)) {
return false;
}
v = p[0]; w = p[1];
SSE_REASSOC_BARRIER(v, w);
v |= p[2]; w |= p[3];
SSE_REASSOC_BARRIER(v, w);
v |= p[4]; w |= p[5];
SSE_REASSOC_BARRIER(v, w);
v |= p[6]; w |= p[7];
SSE_REASSOC_BARRIER(v, w);
v |= w;
}
return _mm256_movemask_epi8(_mm256_cmpeq_epi8(v, zero)) == 0xFFFFFFFF;
}
#endif /* CONFIG_AVX2_OPT */
static biz_accel_fn const accel_table[] = {
buffer_is_zero_int_ge256,
buffer_zero_sse2,
#ifdef CONFIG_AVX2_OPT
buffer_zero_avx2,
#endif
};
static unsigned best_accel(void)
{
#ifdef CONFIG_AVX2_OPT
unsigned info = cpuinfo_init();
if (info & CPUINFO_AVX2) {
return 2;
}
#endif
return 1;
}
#else
# include "host/include/generic/host/bufferiszero.c.inc"
#endif
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