AuroraMiddleware/qt5base-lts
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QString: don't let the compiler emit unnecessary looping

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When AVX2 was enabled, we know we don't need to loop in qt_is_ascii()
(QtPrivate::isAscii(QLatin1String)).

Pick-to: 6.3 6.2
Change-Id: Ib42b3adc93bf4d43bd55fffd16c14f8f95ae8678
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
This commit is contained in:
Thiago Macieira 2021-12-16 15:26:57 -03:00
parent 449f6d5f61
commit 1a9e7a3aad
1 changed files with 6 additions and 0 deletions
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6
src/corelib/text/qstring.cpp
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@ -474,6 +474,7 @@ bool qt_is_ascii(const char *&ptr, const char *end) noexcept
{ {
#if defined(__SSE2__) #if defined(__SSE2__)
// Testing for the high bit can be done efficiently with just PMOVMSKB // Testing for the high bit can be done efficiently with just PMOVMSKB
bool loops = true;
# if defined(__AVX2__) # if defined(__AVX2__)
while (ptr + 32 <= end) { while (ptr + 32 <= end) {
__m256i data = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(ptr)); __m256i data = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(ptr));
@ -485,7 +486,9 @@ bool qt_is_ascii(const char *&ptr, const char *end) noexcept
} }
ptr += 32; ptr += 32;
} }
loops = false;
# endif # endif
while (ptr + 16 <= end) { while (ptr + 16 <= end) {
__m128i data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(ptr)); __m128i data = _mm_loadu_si128(reinterpret_cast<const __m128i *>(ptr));
quint32 mask = _mm_movemask_epi8(data); quint32 mask = _mm_movemask_epi8(data);
@ -495,6 +498,9 @@ bool qt_is_ascii(const char *&ptr, const char *end) noexcept
return false; return false;
} }
ptr += 16; ptr += 16;
if (!loops)
break;
} }
if (ptr + 8 <= end) { if (ptr + 8 <= end) {
__m128i data = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(ptr)); __m128i data = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(ptr));