5e33a87222
Allow selection of several acceleration functions based on the size and alignment of the buffer. Do not require ifunc support for AVX2 acceleration. Signed-off-by: Richard Henderson <rth@twiddle.net> Message-Id: <1472496380-19706-5-git-send-email-rth@twiddle.net> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
235 lines
7.6 KiB
C
235 lines
7.6 KiB
C
/*
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* Simple C functions to supplement the C library
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*
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* Copyright (c) 2006 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu/osdep.h"
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#include "qemu-common.h"
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#include "qemu/cutils.h"
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#include "qemu/bswap.h"
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/* vector definitions */
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extern void link_error(void);
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#define ACCEL_BUFFER_ZERO(NAME, SIZE, VECTYPE, NONZERO) \
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static bool NAME(const void *buf, size_t len) \
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{ \
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const void *end = buf + len; \
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do { \
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const VECTYPE *p = buf; \
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VECTYPE t; \
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if (SIZE == sizeof(VECTYPE) * 4) { \
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t = (p[0] | p[1]) | (p[2] | p[3]); \
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} else if (SIZE == sizeof(VECTYPE) * 8) { \
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t = p[0] | p[1]; \
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t |= p[2] | p[3]; \
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t |= p[4] | p[5]; \
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t |= p[6] | p[7]; \
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} else { \
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link_error(); \
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} \
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if (unlikely(NONZERO(t))) { \
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return false; \
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} \
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buf += SIZE; \
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} while (buf < end); \
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return true; \
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}
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static bool
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buffer_zero_int(const void *buf, size_t len)
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{
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if (unlikely(len < 8)) {
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/* For a very small buffer, simply accumulate all the bytes. */
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const unsigned char *p = buf;
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const unsigned char *e = buf + len;
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unsigned char t = 0;
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do {
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t |= *p++;
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} while (p < e);
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return t == 0;
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} else {
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/* Otherwise, use the unaligned memory access functions to
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handle the beginning and end of the buffer, with a couple
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of loops handling the middle aligned section. */
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uint64_t t = ldq_he_p(buf);
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const uint64_t *p = (uint64_t *)(((uintptr_t)buf + 8) & -8);
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const uint64_t *e = (uint64_t *)(((uintptr_t)buf + len) & -8);
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for (; p + 8 <= e; p += 8) {
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__builtin_prefetch(p + 8);
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if (t) {
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return false;
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}
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t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7];
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}
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while (p < e) {
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t |= *p++;
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}
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t |= ldq_he_p(buf + len - 8);
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return t == 0;
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}
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}
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#if defined(__ALTIVEC__)
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#include <altivec.h>
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/* The altivec.h header says we're allowed to undef these for
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* C++ compatibility. Here we don't care about C++, but we
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* undef them anyway to avoid namespace pollution.
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* altivec.h may redefine the bool macro as vector type.
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* Reset it to POSIX semantics.
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*/
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#undef vector
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#undef pixel
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#undef bool
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#define bool _Bool
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#define DO_NONZERO(X) vec_any_ne(X, (__vector unsigned char){ 0 })
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ACCEL_BUFFER_ZERO(buffer_zero_ppc, 128, __vector unsigned char, DO_NONZERO)
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static bool select_accel_fn(const void *buf, size_t len)
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{
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uintptr_t ibuf = (uintptr_t)buf;
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if (len % 128 == 0 && ibuf % sizeof(__vector unsigned char) == 0) {
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return buffer_zero_ppc(buf, len);
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}
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return buffer_zero_int(buf, len);
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}
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#elif defined(CONFIG_AVX2_OPT) || (defined(CONFIG_CPUID_H) && defined(__SSE2__))
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#include <cpuid.h>
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/* Do not use push_options pragmas unnecessarily, because clang
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* does not support them.
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*/
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#ifndef __SSE2__
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#pragma GCC push_options
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#pragma GCC target("sse2")
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#endif
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#include <emmintrin.h>
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#define SSE2_NONZERO(X) \
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(_mm_movemask_epi8(_mm_cmpeq_epi8((X), _mm_setzero_si128())) != 0xFFFF)
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ACCEL_BUFFER_ZERO(buffer_zero_sse2, 64, __m128i, SSE2_NONZERO)
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#ifndef __SSE2__
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#pragma GCC pop_options
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#endif
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#ifdef CONFIG_AVX2_OPT
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#pragma GCC push_options
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#pragma GCC target("avx2")
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#include <immintrin.h>
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#define AVX2_NONZERO(X) !_mm256_testz_si256((X), (X))
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ACCEL_BUFFER_ZERO(buffer_zero_avx2, 128, __m256i, AVX2_NONZERO)
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#pragma GCC pop_options
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#endif
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#define CACHE_AVX2 2
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#define CACHE_AVX1 4
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#define CACHE_SSE4 8
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#define CACHE_SSE2 16
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static unsigned cpuid_cache;
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static void __attribute__((constructor)) init_cpuid_cache(void)
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{
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int max = __get_cpuid_max(0, NULL);
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int a, b, c, d;
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unsigned cache = 0;
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if (max >= 1) {
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__cpuid(1, a, b, c, d);
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if (d & bit_SSE2) {
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cache |= CACHE_SSE2;
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}
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#ifdef CONFIG_AVX2_OPT
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if (c & bit_SSE4_1) {
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cache |= CACHE_SSE4;
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}
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/* We must check that AVX is not just available, but usable. */
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if ((c & bit_OSXSAVE) && (c & bit_AVX)) {
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__asm("xgetbv" : "=a"(a), "=d"(d) : "c"(0));
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if ((a & 6) == 6) {
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cache |= CACHE_AVX1;
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if (max >= 7) {
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__cpuid_count(7, 0, a, b, c, d);
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if (b & bit_AVX2) {
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cache |= CACHE_AVX2;
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}
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}
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}
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}
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#endif
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}
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cpuid_cache = cache;
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}
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static bool select_accel_fn(const void *buf, size_t len)
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{
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uintptr_t ibuf = (uintptr_t)buf;
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#ifdef CONFIG_AVX2_OPT
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if (len % 128 == 0 && ibuf % 32 == 0 && (cpuid_cache & CACHE_AVX2)) {
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return buffer_zero_avx2(buf, len);
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}
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#endif
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if (len % 64 == 0 && ibuf % 16 == 0 && (cpuid_cache & CACHE_SSE2)) {
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return buffer_zero_sse2(buf, len);
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}
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return buffer_zero_int(buf, len);
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}
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#elif defined(__aarch64__)
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#include "arm_neon.h"
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#define DO_NONZERO(X) (vgetq_lane_u64((X), 0) | vgetq_lane_u64((X), 1))
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ACCEL_BUFFER_ZERO(buffer_zero_neon, 128, uint64x2_t, DO_NONZERO)
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static bool select_accel_fn(const void *buf, size_t len)
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{
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uintptr_t ibuf = (uintptr_t)buf;
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if (len % 128 == 0 && ibuf % sizeof(uint64x2_t) == 0) {
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return buffer_zero_neon(buf, len);
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}
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return buffer_zero_int(buf, len);
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}
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#else
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#define select_accel_fn buffer_zero_int
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#endif
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/*
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* Checks if a buffer is all zeroes
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*/
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bool buffer_is_zero(const void *buf, size_t len)
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{
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if (unlikely(len == 0)) {
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return true;
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}
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/* Use an optimized zero check if possible. Note that this also
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includes a check for an unrolled loop over 64-bit integers. */
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return select_accel_fn(buf, len);
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}
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