/* * Simple C functions to supplement the C library * * Copyright (c) 2006 Fabrice Bellard * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include "qemu/osdep.h" #include "qemu/cutils.h" #include "qemu/bswap.h" #include "host/cpuinfo.h" static bool (*buffer_is_zero_accel)(const void *, size_t); static bool buffer_is_zero_integer(const void *buf, size_t len) { if (unlikely(len < 8)) { /* For a very small buffer, simply accumulate all the bytes. */ const unsigned char *p = buf; const unsigned char *e = buf + len; unsigned char t = 0; do { t |= *p++; } while (p < e); return t == 0; } else { /* Otherwise, use the unaligned memory access functions to handle the beginning and end of the buffer, with a couple of loops handling the middle aligned section. */ uint64_t t = ldq_he_p(buf); const uint64_t *p = (uint64_t *)(((uintptr_t)buf + 8) & -8); const uint64_t *e = (uint64_t *)(((uintptr_t)buf + len) & -8); for (; p + 8 <= e; p += 8) { __builtin_prefetch(p + 8); if (t) { return false; } t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7]; } while (p < e) { t |= *p++; } t |= ldq_he_p(buf + len - 8); return t == 0; } } #if defined(CONFIG_AVX2_OPT) || defined(__SSE2__) #include <immintrin.h> /* Note that each of these vectorized functions require len >= 64. */ static bool __attribute__((target("sse2"))) buffer_zero_sse2(const void *buf, size_t len) { __m128i t = _mm_loadu_si128(buf); __m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16); __m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16); __m128i zero = _mm_setzero_si128(); /* Loop over 16-byte aligned blocks of 64. */ while (likely(p <= e)) { __builtin_prefetch(p); t = _mm_cmpeq_epi8(t, zero); if (unlikely(_mm_movemask_epi8(t) != 0xFFFF)) { return false; } t = p[-4] | p[-3] | p[-2] | p[-1]; p += 4; } /* Finish the aligned tail. */ t |= e[-3]; t |= e[-2]; t |= e[-1]; /* Finish the unaligned tail. */ t |= _mm_loadu_si128(buf + len - 16); return _mm_movemask_epi8(_mm_cmpeq_epi8(t, zero)) == 0xFFFF; } #ifdef CONFIG_AVX2_OPT static bool __attribute__((target("avx2"))) buffer_zero_avx2(const void *buf, size_t len) { /* Begin with an unaligned head of 32 bytes. */ __m256i t = _mm256_loadu_si256(buf); __m256i *p = (__m256i *)(((uintptr_t)buf + 5 * 32) & -32); __m256i *e = (__m256i *)(((uintptr_t)buf + len) & -32); /* Loop over 32-byte aligned blocks of 128. */ while (p <= e) { __builtin_prefetch(p); if (unlikely(!_mm256_testz_si256(t, t))) { return false; } t = p[-4] | p[-3] | p[-2] | p[-1]; p += 4; } ; /* Finish the last block of 128 unaligned. */ t |= _mm256_loadu_si256(buf + len - 4 * 32); t |= _mm256_loadu_si256(buf + len - 3 * 32); t |= _mm256_loadu_si256(buf + len - 2 * 32); t |= _mm256_loadu_si256(buf + len - 1 * 32); return _mm256_testz_si256(t, t); } #endif /* CONFIG_AVX2_OPT */ static unsigned __attribute__((noinline)) select_accel_cpuinfo(unsigned info) { /* Array is sorted in order of algorithm preference. */ static const struct { unsigned bit; bool (*fn)(const void *, size_t); } all[] = { #ifdef CONFIG_AVX2_OPT { CPUINFO_AVX2, buffer_zero_avx2 }, #endif { CPUINFO_SSE2, buffer_zero_sse2 }, { CPUINFO_ALWAYS, buffer_is_zero_integer }, }; for (unsigned i = 0; i < ARRAY_SIZE(all); ++i) { if (info & all[i].bit) { buffer_is_zero_accel = all[i].fn; return all[i].bit; } } return 0; } static unsigned used_accel; static void __attribute__((constructor)) init_accel(void) { used_accel = select_accel_cpuinfo(cpuinfo_init()); } #define INIT_ACCEL NULL bool test_buffer_is_zero_next_accel(void) { /* * Accumulate the accelerators that we've already tested, and * remove them from the set to test this round. We'll get back * a zero from select_accel_cpuinfo when there are no more. */ unsigned used = select_accel_cpuinfo(cpuinfo & ~used_accel); used_accel |= used; return used; } #else bool test_buffer_is_zero_next_accel(void) { return false; } #define INIT_ACCEL buffer_is_zero_integer #endif static bool (*buffer_is_zero_accel)(const void *, size_t) = INIT_ACCEL; bool buffer_is_zero_ool(const void *buf, size_t len) { if (unlikely(len == 0)) { return true; } if (!buffer_is_zero_sample3(buf, len)) { return false; } /* All bytes are covered for any len <= 3. */ if (unlikely(len <= 3)) { return true; } if (likely(len >= 256)) { return buffer_is_zero_accel(buf, len); } return buffer_is_zero_integer(buf, len); } bool buffer_is_zero_ge256(const void *buf, size_t len) { return buffer_is_zero_accel(buf, len); }