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QString::toLatin1: do the same as fromLatin1 for sub-16 characters

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Perform a pair of overlapped loads & stores, so we can perform the
contracting and inserting of question marks in vector code.

Change-Id: Ib42b3adc93bf4d43bd55fffd16c2f5e479b0f6fa
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
This commit is contained in:
Thiago Macieira 2021-12-22 00:26:15 -03:00
parent 3ef43ca837
commit 339aa99fec
1 changed files with 29 additions and 30 deletions
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59
src/corelib/text/qstring.cpp
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@ -955,10 +955,9 @@ static void qt_to_latin1_internal(uchar *dst, const char16_t *src, qsizetype len
return _mm_packus_epi16(chunk1, chunk2);
};
uchar *e = dst + length;
qptrdiff offset = 0;
if (size_t(length) >= sizeof(__m128i)) {
// because of possible overlapping, we won't process the last chunk in the loop
qptrdiff offset = 0;
for ( ; offset + 2 * sizeof(__m128i) < size_t(length); offset += sizeof(__m128i))
_mm_storeu_si128(reinterpret_cast<__m128i *>(dst + offset), loadChunkAt(offset));
@ -971,45 +970,45 @@ static void qt_to_latin1_internal(uchar *dst, const char16_t *src, qsizetype len
}
# if !defined(__OPTIMIZE_SIZE__)
// we're going to write to dst[offset..offset+7] (8 bytes)
if (dst + offset + 7 < e) {
__m128i chunk = _mm_loadu_si128(reinterpret_cast<const __m128i *>(src + offset));
chunk = mergeQuestionMarks(chunk);
if (length >= 4) {
// this code is fine even for in-place conversion because we load both
// before any store
if (length >= 8) {
__m128i chunk1 = _mm_loadu_si128(reinterpret_cast<const __m128i *>(src));
__m128i chunk2 = _mm_loadu_si128(reinterpret_cast<const __m128i *>(src + length - 8));
chunk1 = mergeQuestionMarks(chunk1);
chunk2 = mergeQuestionMarks(chunk2);
// pack, where the upper half is ignored
const __m128i result = _mm_packus_epi16(chunk, chunk);
_mm_storel_epi64(reinterpret_cast<__m128i *>(dst + offset), result);
offset += 8;
}
// pack, where the upper half is ignored
const __m128i result1 = _mm_packus_epi16(chunk1, chunk1);
const __m128i result2 = _mm_packus_epi16(chunk2, chunk2);
_mm_storel_epi64(reinterpret_cast<__m128i *>(dst), result1);
_mm_storel_epi64(reinterpret_cast<__m128i *>(dst + length - 8), result2);
} else {
__m128i chunk1 = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(src));
__m128i chunk2 = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(src + length - 4));
chunk1 = mergeQuestionMarks(chunk1);
chunk2 = mergeQuestionMarks(chunk2);
// we're going to write to dst[offset..offset+3] (4 bytes)
if (dst + offset + 3 < e) {
__m128i chunk = _mm_loadl_epi64(reinterpret_cast<const __m128i *>(src + offset));
chunk = mergeQuestionMarks(chunk);
// pack, we'll the upper three quarters
const __m128i result = _mm_packus_epi16(chunk, chunk);
qToUnaligned(_mm_cvtsi128_si32(result), dst + offset);
offset += 4;
// pack, we'll zero the upper three quarters
const __m128i result1 = _mm_packus_epi16(chunk1, chunk1);
const __m128i result2 = _mm_packus_epi16(chunk2, chunk2);
qToUnaligned(_mm_cvtsi128_si32(result1), dst);
qToUnaligned(_mm_cvtsi128_si32(result2), dst + length - 4);
}
return;
}
length = length % 4;
# else
length = length % 16;
# endif // optimize size
// advance dst, src for tail processing
dst += offset;
src += offset;
# if !defined(__OPTIMIZE_SIZE__)
return UnrollTailLoop<3>::exec(length, [=](qsizetype i) {
if (Checked)
dst[i] = (src[i]>0xff) ? '?' : (uchar) src[i];
else
dst[i] = src[i];
});
# endif
# else
length = length % 16;
# endif // optimize size
#elif defined(__ARM_NEON__)
// Refer to the documentation of the SSE2 implementation.
// This uses exactly the same method as for SSE except: