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authorAlexander Monakov <amonakov@ispras.ru>2024-02-06 23:48:07 +0300
committerRichard Henderson <richard.henderson@linaro.org>2024-05-03 08:03:05 -0700
commit93a6085618f16fb2cd316d1e84f1a638b7e2d8ff (patch)
tree68e4b09262ecdf1029e21b95ac5009ba53212579
parentcbe3d5264631aa193fd2705820cbde6c5a602abb (diff)
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util/bufferiszero: Remove useless prefetches
Use of prefetching in bufferiszero.c is quite questionable: - prefetches are issued just a few CPU cycles before the corresponding line would be hit by demand loads; - they are done for simple access patterns, i.e. where hardware prefetchers can perform better; - they compete for load ports in loops that should be limited by load port throughput rather than ALU throughput. Signed-off-by: Alexander Monakov <amonakov@ispras.ru> Signed-off-by: Mikhail Romanov <mmromanov@ispras.ru> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20240206204809.9859-5-amonakov@ispras.ru>
-rw-r--r--util/bufferiszero.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/util/bufferiszero.c b/util/bufferiszero.c
index 972f394..00118d6 100644
--- a/util/bufferiszero.c
+++ b/util/bufferiszero.c
@@ -50,7 +50,6 @@ static bool buffer_is_zero_integer(const void *buf, size_t len)
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;
}
@@ -80,7 +79,6 @@ buffer_zero_sse2(const void *buf, size_t len)
/* 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;
@@ -111,7 +109,6 @@ buffer_zero_avx2(const void *buf, size_t len)
/* Loop over 32-byte aligned blocks of 128. */
while (p <= e) {
- __builtin_prefetch(p);
if (unlikely(!_mm256_testz_si256(t, t))) {
return false;
}