From fff9f5047af79e7a8bd7345d9f22126d626e35a7 Mon Sep 17 00:00:00 2001 From: Thiago Macieira Date: Fri, 2 Feb 2024 22:58:45 -0800 Subject: [PATCH] qHash: update the pre-AVX512 mask to use the cacheline size MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit No change in behavior. But instead of trying to guess if we're going to cross a page boundary, we check for the cacheline: if we don't cross a cacheline boundary, then we can't cross a page boundary either. Testing bit 4 can be implemented with a shorter instruction than a test for bit 11. f43de: 40 f6 c7 20 test $0x20,%dil Change-Id: I664b9f014ffc48cbb49bfffd17b04817a0fb8c6b Reviewed-by: Mårten Nordheim --- src/corelib/tools/qhash.cpp | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp index 8077141795..87ccc46d71 100644 --- a/src/corelib/tools/qhash.cpp +++ b/src/corelib/tools/qhash.cpp @@ -756,16 +756,16 @@ aeshash128_lt16(__m128i state0, const __m128i *src, const __m128i *srcend, size_ // including NULLs at the end because the length is in the key) // WARNING: this may produce valgrind warnings, but it's safe - constexpr quintptr PageSize = 4096; + constexpr quintptr CachelineSize = 64; __m128i data; - if ((quintptr(src) & (PageSize / 2)) == 0) { - // lower half of the page: + if ((quintptr(src) & (CachelineSize / 2)) == 0) { + // lower half of the cacheline: __m128i mask = _mm_loadu_si128(reinterpret_cast(maskarray + 15 - len)); data = loadu128(src); data = _mm_and_si128(data, mask); } else { - // upper half of the page: + // upper half of the cacheline: __m128i control = _mm_loadu_si128(reinterpret_cast(shufflecontrol + 15 - len)); data = loadu128(advance(srcend, -1)); data = _mm_shuffle_epi8(data, control);