qemu

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/*
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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/cutils.h"
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#include "qemu/bswap.h"
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#include "host/cpuinfo.h"
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typedef bool (*biz_accel_fn)(const void *, size_t);
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static bool buffer_is_zero_int_lt256(const void *buf, size_t len)
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{
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    uint64_t t;
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    const uint64_t *p, *e;
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    /*
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     * Use unaligned memory access functions to handle
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     * the beginning and end of the buffer.
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     */
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    if (unlikely(len <= 8)) {
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        return (ldl_he_p(buf) | ldl_he_p(buf + len - 4)) == 0;
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    }
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    t = ldq_he_p(buf) | ldq_he_p(buf + len - 8);
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    p = QEMU_ALIGN_PTR_DOWN(buf + 8, 8);
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    e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8);
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    /* Read 0 to 31 aligned words from the middle. */
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    while (p < e) {
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        t |= *p++;
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    }
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    return t == 0;
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}
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static bool buffer_is_zero_int_ge256(const void *buf, size_t len)
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{
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    /*
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     * Use unaligned memory access functions to handle
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     * the beginning and end of the buffer.
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     */
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    uint64_t t = ldq_he_p(buf) | ldq_he_p(buf + len - 8);
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    const uint64_t *p = QEMU_ALIGN_PTR_DOWN(buf + 8, 8);
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    const uint64_t *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8);
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    /* Collect a partial block at the tail end. */
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    t |= e[-7] | e[-6] | e[-5] | e[-4] | e[-3] | e[-2] | e[-1];
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    /*
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     * Loop over 64 byte blocks.
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     * With the head and tail removed, e - p >= 30,
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     * so the loop must iterate at least 3 times.
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     */
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    do {
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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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        p += 8;
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    } while (p < e - 7);
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    return t == 0;
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}
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#include "host/bufferiszero.c.inc"
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static biz_accel_fn buffer_is_zero_accel;
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static unsigned accel_index;
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bool buffer_is_zero_ool(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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    if (!buffer_is_zero_sample3(buf, len)) {
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        return false;
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    }
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    /* All bytes are covered for any len <= 3.  */
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    if (unlikely(len <= 3)) {
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        return true;
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    }
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    if (likely(len >= 256)) {
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        return buffer_is_zero_accel(buf, len);
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    }
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    return buffer_is_zero_int_lt256(buf, len);
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}
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bool buffer_is_zero_ge256(const void *buf, size_t len)
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{
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    return buffer_is_zero_accel(buf, len);
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}
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bool test_buffer_is_zero_next_accel(void)
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{
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    if (accel_index != 0) {
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        buffer_is_zero_accel = accel_table[--accel_index];
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        return true;
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    }
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    return false;
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}
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static void __attribute__((constructor)) init_accel(void)
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{
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    accel_index = best_accel();
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    buffer_is_zero_accel = accel_table[accel_index];
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}
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