mirror of
https://gitlab.com/qemu-project/qemu
synced 2024-10-14 15:02:54 +00:00
util/bufferiszero:
- Remove sse4.1 and avx512 variants - Reorganize for early test for acceleration - Remove useless prefetches - Optimize sse2, avx2 and integer variants - Add simd acceleration for aarch64 - Add bufferiszero-bench -----BEGIN PGP SIGNATURE----- iQFRBAABCgA7FiEEekgeeIaLTbaoWgXAZN846K9+IV8FAmY0/qMdHHJpY2hhcmQu aGVuZGVyc29uQGxpbmFyby5vcmcACgkQZN846K9+IV+ULQf/T2JSdvG6/EjDCf4N cnSGiUV2MIeByw8tkrc/fWCNdlulHhk9gbg9l+f2muwK8H/k2BdynbrQnt1Ymmtk xzM6+PNOcByaovSAkvNweZVbrQX36Yih9S7f3n+xcxfVuvvYhKSLHXLkeqO96LMd rN+WRpxhReaU3n8/FO7o3S26SRpk7X9kRfShaT7U7ytHGjGsXUvMKIRs30hbsJTB yjed0a0u54FoSlN6AEqjWdgzaWP8nT65+8Yxe3dzB9hx09UiolZo60eHqYy7Mkno N6aMOB6gUUbCiKZ3Qk+1zEX97vl26NH3zt5tIIJTWDoIkC3f9qbg1x5hwWLQ3rra rM8h8w== =DnZO -----END PGP SIGNATURE----- Merge tag 'pull-misc-20240503' of https://gitlab.com/rth7680/qemu into staging util/bufferiszero: - Remove sse4.1 and avx512 variants - Reorganize for early test for acceleration - Remove useless prefetches - Optimize sse2, avx2 and integer variants - Add simd acceleration for aarch64 - Add bufferiszero-bench # -----BEGIN PGP SIGNATURE----- # # iQFRBAABCgA7FiEEekgeeIaLTbaoWgXAZN846K9+IV8FAmY0/qMdHHJpY2hhcmQu # aGVuZGVyc29uQGxpbmFyby5vcmcACgkQZN846K9+IV+ULQf/T2JSdvG6/EjDCf4N # cnSGiUV2MIeByw8tkrc/fWCNdlulHhk9gbg9l+f2muwK8H/k2BdynbrQnt1Ymmtk # xzM6+PNOcByaovSAkvNweZVbrQX36Yih9S7f3n+xcxfVuvvYhKSLHXLkeqO96LMd # rN+WRpxhReaU3n8/FO7o3S26SRpk7X9kRfShaT7U7ytHGjGsXUvMKIRs30hbsJTB # yjed0a0u54FoSlN6AEqjWdgzaWP8nT65+8Yxe3dzB9hx09UiolZo60eHqYy7Mkno # N6aMOB6gUUbCiKZ3Qk+1zEX97vl26NH3zt5tIIJTWDoIkC3f9qbg1x5hwWLQ3rra # rM8h8w== # =DnZO # -----END PGP SIGNATURE----- # gpg: Signature made Fri 03 May 2024 08:11:31 AM PDT # gpg: using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F # gpg: issuer "richard.henderson@linaro.org" # gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [ultimate] * tag 'pull-misc-20240503' of https://gitlab.com/rth7680/qemu: tests/bench: Add bufferiszero-bench util/bufferiszero: Add simd acceleration for aarch64 util/bufferiszero: Simplify test_buffer_is_zero_next_accel util/bufferiszero: Introduce biz_accel_fn typedef util/bufferiszero: Improve scalar variant util/bufferiszero: Optimize SSE2 and AVX2 variants util/bufferiszero: Remove useless prefetches util/bufferiszero: Reorganize for early test for acceleration util/bufferiszero: Remove AVX512 variant util/bufferiszero: Remove SSE4.1 variant Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson
commit
909aff7eaf
|
|
@ -187,9 +187,39 @@ char *freq_to_str(uint64_t freq_hz);
|
|||
/* used to print char* safely */
|
||||
#define STR_OR_NULL(str) ((str) ? (str) : "null")
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||||
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bool buffer_is_zero(const void *buf, size_t len);
|
||||
/*
|
||||
* Check if a buffer is all zeroes.
|
||||
*/
|
||||
|
||||
bool buffer_is_zero_ool(const void *vbuf, size_t len);
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bool buffer_is_zero_ge256(const void *vbuf, size_t len);
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bool test_buffer_is_zero_next_accel(void);
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||||
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static inline bool buffer_is_zero_sample3(const char *buf, size_t len)
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||||
{
|
||||
/*
|
||||
* For any reasonably sized buffer, these three samples come from
|
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* three different cachelines. In qemu-img usage, we find that
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* each byte eliminates more than half of all buffer testing.
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* It is therefore critical to performance that the byte tests
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* short-circuit, so that we do not pull in additional cache lines.
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* Do not "optimize" this to !(a | b | c).
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*/
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return !buf[0] && !buf[len - 1] && !buf[len / 2];
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}
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#ifdef __OPTIMIZE__
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static inline bool buffer_is_zero(const void *buf, size_t len)
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{
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return (__builtin_constant_p(len) && len >= 256
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? buffer_is_zero_sample3(buf, len) &&
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buffer_is_zero_ge256(buf, len)
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: buffer_is_zero_ool(buf, len));
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}
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#else
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#define buffer_is_zero buffer_is_zero_ool
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#endif
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/*
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* Implementation of ULEB128 (http://en.wikipedia.org/wiki/LEB128)
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* Input is limited to 14-bit numbers
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|
|
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47
tests/bench/bufferiszero-bench.c
Normal file
47
tests/bench/bufferiszero-bench.c
Normal file
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@ -0,0 +1,47 @@
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/*
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* QEMU buffer_is_zero speed benchmark
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* (at your option) any later version. See the COPYING file in the
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* top-level directory.
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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/units.h"
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static void test(const void *opaque)
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{
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size_t max = 64 * KiB;
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void *buf = g_malloc0(max);
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int accel_index = 0;
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do {
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if (accel_index != 0) {
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g_test_message("%s", ""); /* gnu_printf Werror for simple "" */
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}
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for (size_t len = 1 * KiB; len <= max; len *= 4) {
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double total = 0.0;
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g_test_timer_start();
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do {
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buffer_is_zero_ge256(buf, len);
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total += len;
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} while (g_test_timer_elapsed() < 0.5);
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total /= MiB;
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g_test_message("buffer_is_zero #%d: %2zuKB %8.0f MB/sec",
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accel_index, len / (size_t)KiB,
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total / g_test_timer_last());
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}
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accel_index++;
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} while (test_buffer_is_zero_next_accel());
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g_free(buf);
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}
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int main(int argc, char **argv)
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{
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g_test_init(&argc, &argv, NULL);
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g_test_add_data_func("/cutils/bufferiszero/speed", NULL, test);
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return g_test_run();
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}
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|
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@ -21,6 +21,7 @@ benchs = {}
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|
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if have_block
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benchs += {
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'bufferiszero-bench': [],
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'benchmark-crypto-hash': [crypto],
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'benchmark-crypto-hmac': [crypto],
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'benchmark-crypto-cipher': [crypto],
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||||
|
|
|
|||
|
|
@ -26,265 +26,290 @@
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#include "qemu/bswap.h"
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#include "host/cpuinfo.h"
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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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typedef bool (*biz_accel_fn)(const void *, size_t);
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|
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static bool buffer_is_zero_int_lt256(const void *buf, size_t len)
|
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{
|
||||
if (unlikely(len < 8)) {
|
||||
/* For a very small buffer, simply accumulate all the bytes. */
|
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const unsigned char *p = buf;
|
||||
const unsigned char *e = buf + len;
|
||||
unsigned char t = 0;
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uint64_t t;
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const uint64_t *p, *e;
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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
|
||||
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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||||
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return t == 0;
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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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||||
|
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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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#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
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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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*/
|
||||
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 {
|
||||
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;
|
||||
} while (p < e - 7);
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||||
|
||||
return t == 0;
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||||
}
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||||
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#if defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
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#include <immintrin.h>
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||||
|
||||
/* Note that each of these vectorized functions require len >= 64. */
|
||||
/* Helper for preventing the compiler from reassociating
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||||
chains of binary vector operations. */
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||||
#define SSE_REASSOC_BARRIER(vec0, vec1) asm("" : "+x"(vec0), "+x"(vec1))
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||||
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||||
/* Note that these vectorized functions may assume len >= 256. */
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||||
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||||
static bool __attribute__((target("sse2")))
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||||
buffer_zero_sse2(const void *buf, size_t len)
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||||
{
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__m128i t = _mm_loadu_si128(buf);
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__m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
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__m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
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__m128i zero = _mm_setzero_si128();
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||||
/* Unaligned loads at head/tail. */
|
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__m128i v = *(__m128i_u *)(buf);
|
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__m128i w = *(__m128i_u *)(buf + len - 16);
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/* Align head/tail to 16-byte boundaries. */
|
||||
const __m128i *p = QEMU_ALIGN_PTR_DOWN(buf + 16, 16);
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const __m128i *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 16);
|
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__m128i zero = { 0 };
|
||||
|
||||
/* Loop over 16-byte aligned blocks of 64. */
|
||||
while (likely(p <= e)) {
|
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__builtin_prefetch(p);
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t = _mm_cmpeq_epi8(t, zero);
|
||||
if (unlikely(_mm_movemask_epi8(t) != 0xFFFF)) {
|
||||
/* Collect a partial block at tail end. */
|
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v |= e[-1]; w |= e[-2];
|
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SSE_REASSOC_BARRIER(v, w);
|
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v |= e[-3]; w |= e[-4];
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SSE_REASSOC_BARRIER(v, w);
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v |= e[-5]; w |= e[-6];
|
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SSE_REASSOC_BARRIER(v, w);
|
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v |= e[-7]; v |= w;
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|
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/*
|
||||
* Loop over complete 128-byte blocks.
|
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* With the head and tail removed, e - p >= 14, so the loop
|
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* must iterate at least once.
|
||||
*/
|
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do {
|
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v = _mm_cmpeq_epi8(v, zero);
|
||||
if (unlikely(_mm_movemask_epi8(v) != 0xFFFF)) {
|
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return false;
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}
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t = p[-4] | p[-3] | p[-2] | p[-1];
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p += 4;
|
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}
|
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v = p[0]; w = p[1];
|
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SSE_REASSOC_BARRIER(v, w);
|
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v |= p[2]; w |= p[3];
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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;
|
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p += 8;
|
||||
} while (p < e - 7);
|
||||
|
||||
/* 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;
|
||||
return _mm_movemask_epi8(_mm_cmpeq_epi8(v, zero)) == 0xFFFF;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_AVX2_OPT
|
||||
static bool __attribute__((target("sse4")))
|
||||
buffer_zero_sse4(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);
|
||||
|
||||
/* Loop over 16-byte aligned blocks of 64. */
|
||||
while (likely(p <= e)) {
|
||||
__builtin_prefetch(p);
|
||||
if (unlikely(!_mm_testz_si128(t, t))) {
|
||||
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_testz_si128(t, t);
|
||||
}
|
||||
|
||||
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);
|
||||
/* 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 };
|
||||
|
||||
/* Loop over 32-byte aligned blocks of 128. */
|
||||
while (p <= e) {
|
||||
__builtin_prefetch(p);
|
||||
if (unlikely(!_mm256_testz_si256(t, t))) {
|
||||
/* 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;
|
||||
}
|
||||
t = p[-4] | p[-3] | p[-2] | p[-1];
|
||||
p += 4;
|
||||
} ;
|
||||
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;
|
||||
}
|
||||
|
||||
/* 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);
|
||||
return _mm256_movemask_epi8(_mm256_cmpeq_epi8(v, zero)) == 0xFFFFFFFF;
|
||||
}
|
||||
#endif /* CONFIG_AVX2_OPT */
|
||||
|
||||
#ifdef CONFIG_AVX512F_OPT
|
||||
static bool __attribute__((target("avx512f")))
|
||||
buffer_zero_avx512(const void *buf, size_t len)
|
||||
{
|
||||
/* Begin with an unaligned head of 64 bytes. */
|
||||
__m512i t = _mm512_loadu_si512(buf);
|
||||
__m512i *p = (__m512i *)(((uintptr_t)buf + 5 * 64) & -64);
|
||||
__m512i *e = (__m512i *)(((uintptr_t)buf + len) & -64);
|
||||
|
||||
/* Loop over 64-byte aligned blocks of 256. */
|
||||
while (p <= e) {
|
||||
__builtin_prefetch(p);
|
||||
if (unlikely(_mm512_test_epi64_mask(t, t))) {
|
||||
return false;
|
||||
}
|
||||
t = p[-4] | p[-3] | p[-2] | p[-1];
|
||||
p += 4;
|
||||
}
|
||||
|
||||
t |= _mm512_loadu_si512(buf + len - 4 * 64);
|
||||
t |= _mm512_loadu_si512(buf + len - 3 * 64);
|
||||
t |= _mm512_loadu_si512(buf + len - 2 * 64);
|
||||
t |= _mm512_loadu_si512(buf + len - 1 * 64);
|
||||
|
||||
return !_mm512_test_epi64_mask(t, t);
|
||||
|
||||
}
|
||||
#endif /* CONFIG_AVX512F_OPT */
|
||||
|
||||
/*
|
||||
* Make sure that these variables are appropriately initialized when
|
||||
* SSE2 is enabled on the compiler command-line, but the compiler is
|
||||
* too old to support CONFIG_AVX2_OPT.
|
||||
*/
|
||||
#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
|
||||
# define INIT_USED 0
|
||||
# define INIT_LENGTH 0
|
||||
# define INIT_ACCEL buffer_zero_int
|
||||
#else
|
||||
# ifndef __SSE2__
|
||||
# error "ISA selection confusion"
|
||||
# endif
|
||||
# define INIT_USED CPUINFO_SSE2
|
||||
# define INIT_LENGTH 64
|
||||
# define INIT_ACCEL buffer_zero_sse2
|
||||
#endif
|
||||
|
||||
static unsigned used_accel = INIT_USED;
|
||||
static unsigned length_to_accel = INIT_LENGTH;
|
||||
static bool (*buffer_accel)(const void *, size_t) = INIT_ACCEL;
|
||||
|
||||
static unsigned __attribute__((noinline))
|
||||
select_accel_cpuinfo(unsigned info)
|
||||
{
|
||||
/* Array is sorted in order of algorithm preference. */
|
||||
static const struct {
|
||||
unsigned bit;
|
||||
unsigned len;
|
||||
bool (*fn)(const void *, size_t);
|
||||
} all[] = {
|
||||
#ifdef CONFIG_AVX512F_OPT
|
||||
{ CPUINFO_AVX512F, 256, buffer_zero_avx512 },
|
||||
#endif
|
||||
static biz_accel_fn const accel_table[] = {
|
||||
buffer_is_zero_int_ge256,
|
||||
buffer_zero_sse2,
|
||||
#ifdef CONFIG_AVX2_OPT
|
||||
{ CPUINFO_AVX2, 128, buffer_zero_avx2 },
|
||||
{ CPUINFO_SSE4, 64, buffer_zero_sse4 },
|
||||
buffer_zero_avx2,
|
||||
#endif
|
||||
{ CPUINFO_SSE2, 64, buffer_zero_sse2 },
|
||||
{ CPUINFO_ALWAYS, 0, buffer_zero_int },
|
||||
};
|
||||
};
|
||||
|
||||
for (unsigned i = 0; i < ARRAY_SIZE(all); ++i) {
|
||||
if (info & all[i].bit) {
|
||||
length_to_accel = all[i].len;
|
||||
buffer_accel = all[i].fn;
|
||||
return all[i].bit;
|
||||
}
|
||||
static unsigned best_accel(void)
|
||||
{
|
||||
unsigned info = cpuinfo_init();
|
||||
|
||||
#ifdef CONFIG_AVX2_OPT
|
||||
if (info & CPUINFO_AVX2) {
|
||||
return 2;
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
|
||||
static void __attribute__((constructor)) init_accel(void)
|
||||
{
|
||||
used_accel = select_accel_cpuinfo(cpuinfo_init());
|
||||
}
|
||||
#endif /* CONFIG_AVX2_OPT */
|
||||
|
||||
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;
|
||||
}
|
||||
|
||||
static bool select_accel_fn(const void *buf, size_t len)
|
||||
{
|
||||
if (likely(len >= length_to_accel)) {
|
||||
return buffer_accel(buf, len);
|
||||
}
|
||||
return buffer_zero_int(buf, len);
|
||||
}
|
||||
|
||||
#else
|
||||
#define select_accel_fn buffer_zero_int
|
||||
bool test_buffer_is_zero_next_accel(void)
|
||||
{
|
||||
return false;
|
||||
}
|
||||
#endif
|
||||
return info & CPUINFO_SSE2 ? 1 : 0;
|
||||
}
|
||||
|
||||
#elif defined(__aarch64__) && defined(__ARM_NEON)
|
||||
#include <arm_neon.h>
|
||||
|
||||
/*
|
||||
* Checks if a buffer is all zeroes
|
||||
* Helper for preventing the compiler from reassociating
|
||||
* chains of binary vector operations.
|
||||
*/
|
||||
bool buffer_is_zero(const void *buf, size_t len)
|
||||
#define REASSOC_BARRIER(vec0, vec1) asm("" : "+w"(vec0), "+w"(vec1))
|
||||
|
||||
static bool buffer_is_zero_simd(const void *buf, size_t len)
|
||||
{
|
||||
uint32x4_t t0, t1, t2, t3;
|
||||
|
||||
/* Align head/tail to 16-byte boundaries. */
|
||||
const uint32x4_t *p = QEMU_ALIGN_PTR_DOWN(buf + 16, 16);
|
||||
const uint32x4_t *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 16);
|
||||
|
||||
/* Unaligned loads at head/tail. */
|
||||
t0 = vld1q_u32(buf) | vld1q_u32(buf + len - 16);
|
||||
|
||||
/* Collect a partial block at tail end. */
|
||||
t1 = e[-7] | e[-6];
|
||||
t2 = e[-5] | e[-4];
|
||||
t3 = e[-3] | e[-2];
|
||||
t0 |= e[-1];
|
||||
REASSOC_BARRIER(t0, t1);
|
||||
REASSOC_BARRIER(t2, t3);
|
||||
t0 |= t1;
|
||||
t2 |= t3;
|
||||
REASSOC_BARRIER(t0, t2);
|
||||
t0 |= t2;
|
||||
|
||||
/*
|
||||
* Loop over complete 128-byte blocks.
|
||||
* With the head and tail removed, e - p >= 14, so the loop
|
||||
* must iterate at least once.
|
||||
*/
|
||||
do {
|
||||
/*
|
||||
* Reduce via UMAXV. Whatever the actual result,
|
||||
* it will only be zero if all input bytes are zero.
|
||||
*/
|
||||
if (unlikely(vmaxvq_u32(t0) != 0)) {
|
||||
return false;
|
||||
}
|
||||
|
||||
t0 = p[0] | p[1];
|
||||
t1 = p[2] | p[3];
|
||||
t2 = p[4] | p[5];
|
||||
t3 = p[6] | p[7];
|
||||
REASSOC_BARRIER(t0, t1);
|
||||
REASSOC_BARRIER(t2, t3);
|
||||
t0 |= t1;
|
||||
t2 |= t3;
|
||||
REASSOC_BARRIER(t0, t2);
|
||||
t0 |= t2;
|
||||
p += 8;
|
||||
} while (p < e - 7);
|
||||
|
||||
return vmaxvq_u32(t0) == 0;
|
||||
}
|
||||
|
||||
#define best_accel() 1
|
||||
static biz_accel_fn const accel_table[] = {
|
||||
buffer_is_zero_int_ge256,
|
||||
buffer_is_zero_simd,
|
||||
};
|
||||
#else
|
||||
#define best_accel() 0
|
||||
static biz_accel_fn const accel_table[1] = {
|
||||
buffer_is_zero_int_ge256
|
||||
};
|
||||
#endif
|
||||
|
||||
static biz_accel_fn buffer_is_zero_accel;
|
||||
static unsigned accel_index;
|
||||
|
||||
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;
|
||||
}
|
||||
|
||||
/* Fetch the beginning of the buffer while we select the accelerator. */
|
||||
__builtin_prefetch(buf);
|
||||
|
||||
/* 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);
|
||||
if (likely(len >= 256)) {
|
||||
return buffer_is_zero_accel(buf, len);
|
||||
}
|
||||
return buffer_is_zero_int_lt256(buf, len);
|
||||
}
|
||||
|
||||
bool buffer_is_zero_ge256(const void *buf, size_t len)
|
||||
{
|
||||
return buffer_is_zero_accel(buf, len);
|
||||
}
|
||||
|
||||
bool test_buffer_is_zero_next_accel(void)
|
||||
{
|
||||
if (accel_index != 0) {
|
||||
buffer_is_zero_accel = accel_table[--accel_index];
|
||||
return true;
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
static void __attribute__((constructor)) init_accel(void)
|
||||
{
|
||||
accel_index = best_accel();
|
||||
buffer_is_zero_accel = accel_table[accel_index];
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue