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QString: move the body of qustrlen's SSE2 implementation

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Change-Id: I0e5f6bec596a4a78bd3bfffd16c96189533ad94e
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
This commit is contained in:
Thiago Macieira 2022-01-11 17:26:21 -08:00
parent 40083f380f
commit 1acd028b0c
1 changed files with 38 additions and 34 deletions
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72
src/corelib/text/qstring.cpp
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@ -415,6 +415,42 @@ static Q_ALWAYS_INLINE __m128i mm_load8_zero_extend(const void *ptr)
return _mm_unpacklo_epi8(data, _mm_setzero_si128());
}
[[maybe_unused]] ATTRIBUTE_NO_SANITIZE
static qsizetype qustrlen_sse2(const char16_t *str) noexcept
{
// find the 16-byte alignment immediately prior or equal to str
quintptr misalignment = quintptr(str) & 0xf;
Q_ASSERT((misalignment & 1) == 0);
const char16_t *ptr = str - (misalignment / 2);
// load 16 bytes and see if we have a null
// (aligned loads can never segfault)
const __m128i zeroes = _mm_setzero_si128();
__m128i data = _mm_load_si128(reinterpret_cast<const __m128i *>(ptr));
__m128i comparison = _mm_cmpeq_epi16(data, zeroes);
quint32 mask = _mm_movemask_epi8(comparison);
// ignore the result prior to the beginning of str
mask >>= misalignment;
// Have we found something in the first block? Need to handle it now
// because of the left shift above.
if (mask)
return qCountTrailingZeroBits(quint32(mask)) / 2;
do {
ptr += 8;
data = _mm_load_si128(reinterpret_cast<const __m128i *>(ptr));
comparison = _mm_cmpeq_epi16(data, zeroes);
mask = _mm_movemask_epi8(comparison);
} while (mask == 0);
// found a null
uint idx = qCountTrailingZeroBits(quint32(mask));
return ptr - str + idx / 2;
}
// Scans from \a ptr to \a end until \a maskval is non-zero. Returns true if
// the no non-zero was found. Returns false and updates \a ptr to point to the
// first 16-bit word that has any bit set (note: if the input is 8-bit, \a ptr
@ -517,48 +553,16 @@ static bool simdTestMask(const char *&ptr, const char *end, quint32 maskval)
}
#endif
ATTRIBUTE_NO_SANITIZE
qsizetype QtPrivate::qustrlen(const char16_t *str) noexcept
{
qsizetype result = 0;
#if defined(__SSE2__) && !(defined(__SANITIZE_ADDRESS__) || __has_feature(address_sanitizer))
// find the 16-byte alignment immediately prior or equal to str
quintptr misalignment = quintptr(str) & 0xf;
Q_ASSERT((misalignment & 1) == 0);
const char16_t *ptr = str - (misalignment / 2);
// load 16 bytes and see if we have a null
// (aligned loads can never segfault)
const __m128i zeroes = _mm_setzero_si128();
__m128i data = _mm_load_si128(reinterpret_cast<const __m128i *>(ptr));
__m128i comparison = _mm_cmpeq_epi16(data, zeroes);
quint32 mask = _mm_movemask_epi8(comparison);
// ignore the result prior to the beginning of str
mask >>= misalignment;
// Have we found something in the first block? Need to handle it now
// because of the left shift above.
if (mask)
return qCountTrailingZeroBits(quint32(mask)) / 2;
do {
ptr += 8;
data = _mm_load_si128(reinterpret_cast<const __m128i *>(ptr));
comparison = _mm_cmpeq_epi16(data, zeroes);
mask = _mm_movemask_epi8(comparison);
} while (mask == 0);
// found a null
uint idx = qCountTrailingZeroBits(quint32(mask));
return ptr - str + idx / 2;
return qustrlen_sse2(str);
#endif
if (sizeof(wchar_t) == sizeof(char16_t))
return wcslen(reinterpret_cast<const wchar_t *>(str));
qsizetype result = 0;
while (*str++)
++result;
return result;