/* * 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-common.h" #include "qemu/cutils.h" #include "qemu/bswap.h" /* vector definitions */ extern void link_error(void); #define ACCEL_BUFFER_ZERO(NAME, SIZE, VECTYPE, NONZERO) \ static bool NAME(const void *buf, size_t len) \ { \ const void *end = buf + len; \ do { \ const VECTYPE *p = buf; \ VECTYPE t; \ if (SIZE == sizeof(VECTYPE) * 4) { \ t = (p[0] | p[1]) | (p[2] | p[3]); \ } else if (SIZE == sizeof(VECTYPE) * 8) { \ t = p[0] | p[1]; \ t |= p[2] | p[3]; \ t |= p[4] | p[5]; \ t |= p[6] | p[7]; \ } else { \ link_error(); \ } \ if (unlikely(NONZERO(t))) { \ return false; \ } \ buf += SIZE; \ } while (buf < end); \ return true; \ } static bool buffer_zero_int(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(__ALTIVEC__) #include /* The altivec.h header says we're allowed to undef these for * C++ compatibility. Here we don't care about C++, but we * undef them anyway to avoid namespace pollution. * altivec.h may redefine the bool macro as vector type. * Reset it to POSIX semantics. */ #undef vector #undef pixel #undef bool #define bool _Bool #define DO_NONZERO(X) vec_any_ne(X, (__vector unsigned char){ 0 }) ACCEL_BUFFER_ZERO(buffer_zero_ppc, 128, __vector unsigned char, DO_NONZERO) static bool select_accel_fn(const void *buf, size_t len) { uintptr_t ibuf = (uintptr_t)buf; if (len % 128 == 0 && ibuf % sizeof(__vector unsigned char) == 0) { return buffer_zero_ppc(buf, len); } return buffer_zero_int(buf, len); } #elif defined(CONFIG_AVX2_OPT) || (defined(CONFIG_CPUID_H) && defined(__SSE2__)) #include /* Do not use push_options pragmas unnecessarily, because clang * does not support them. */ #ifndef __SSE2__ #pragma GCC push_options #pragma GCC target("sse2") #endif #include #define SSE2_NONZERO(X) \ (_mm_movemask_epi8(_mm_cmpeq_epi8((X), _mm_setzero_si128())) != 0xFFFF) ACCEL_BUFFER_ZERO(buffer_zero_sse2, 64, __m128i, SSE2_NONZERO) #ifndef __SSE2__ #pragma GCC pop_options #endif #ifdef CONFIG_AVX2_OPT #pragma GCC push_options #pragma GCC target("avx2") #include #define AVX2_NONZERO(X) !_mm256_testz_si256((X), (X)) ACCEL_BUFFER_ZERO(buffer_zero_avx2, 128, __m256i, AVX2_NONZERO) #pragma GCC pop_options #endif #define CACHE_AVX2 2 #define CACHE_AVX1 4 #define CACHE_SSE4 8 #define CACHE_SSE2 16 static unsigned cpuid_cache; static void __attribute__((constructor)) init_cpuid_cache(void) { int max = __get_cpuid_max(0, NULL); int a, b, c, d; unsigned cache = 0; if (max >= 1) { __cpuid(1, a, b, c, d); if (d & bit_SSE2) { cache |= CACHE_SSE2; } #ifdef CONFIG_AVX2_OPT if (c & bit_SSE4_1) { cache |= CACHE_SSE4; } /* We must check that AVX is not just available, but usable. */ if ((c & bit_OSXSAVE) && (c & bit_AVX)) { __asm("xgetbv" : "=a"(a), "=d"(d) : "c"(0)); if ((a & 6) == 6) { cache |= CACHE_AVX1; if (max >= 7) { __cpuid_count(7, 0, a, b, c, d); if (b & bit_AVX2) { cache |= CACHE_AVX2; } } } } #endif } cpuid_cache = cache; } static bool select_accel_fn(const void *buf, size_t len) { uintptr_t ibuf = (uintptr_t)buf; #ifdef CONFIG_AVX2_OPT if (len % 128 == 0 && ibuf % 32 == 0 && (cpuid_cache & CACHE_AVX2)) { return buffer_zero_avx2(buf, len); } #endif if (len % 64 == 0 && ibuf % 16 == 0 && (cpuid_cache & CACHE_SSE2)) { return buffer_zero_sse2(buf, len); } return buffer_zero_int(buf, len); } #else #define select_accel_fn buffer_zero_int #endif /* * Checks if a buffer is all zeroes */ bool buffer_is_zero(const void *buf, size_t len) { if (unlikely(len == 0)) { return true; } /* Use an optimized zero check if possible. Note that this also includes a check for an unrolled loop over 64-bit integers. */ return select_accel_fn(buf, len); }