diff options
| author | Thiago Macieira <thiago.macieira@intel.com> | 2022-01-18 11:31:40 -0800 |
|---|---|---|
| committer | Thiago Macieira <thiago.macieira@intel.com> | 2022-01-21 14:08:01 -0800 |
| commit | 517821b1730695dc41403668854871c746face26 (patch) | |
| tree | d70cf2d2ec29a5b630bc7b024e80a6110ddb4452 /src | |
| parent | e1654aeb2e7fa282af045496c4903b06d2893e21 (diff) | |
QHash: improve aeshash's page detection code
We don't need to test for actually crossing a page boundary. It suffices
to check if we're in the upper half or the lower half of the page. In
the upper half, we load ending at the end; in the lower half, we load
starting at the current position. This way, it can never crash.
Pick-to: 6.2.3 6.2 6.3
Change-Id: Icad7c1bad46a449c8e8afffd16cb743e622b3405
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Diffstat (limited to 'src')
| -rw-r--r-- | src/corelib/tools/qhash.cpp | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp index 8f7ffb79b8..0de69ad20a 100644 --- a/src/corelib/tools/qhash.cpp +++ b/src/corelib/tools/qhash.cpp @@ -597,10 +597,11 @@ lt16: // 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; __m128i data; - if (Q_LIKELY(quintptr(src + 1) & 0xff0)) { - // same page, we definitely can't fault: + if ((quintptr(src) & (PageSize / 2)) == 0) { + // lower half of the page: // load all 16 bytes and mask off the bytes past the end of the source static const qint8 maskarray[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, @@ -610,15 +611,14 @@ lt16: data = _mm_loadu_si128(src); data = _mm_and_si128(data, mask); } else { - // too close to the end of the page, it could fault: + // upper half of the page: // load 16 bytes ending at the data end, then shuffle them to the beginning static const qint8 shufflecontrol[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }; __m128i control = _mm_loadu_si128(reinterpret_cast<const __m128i *>(shufflecontrol + 15 - len)); - p = reinterpret_cast<const uchar *>(src - 1); - data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(p + len)); + data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(p + len) - 1); data = _mm_shuffle_epi8(data, control); } |