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-rw-r--r--src/corelib/codecs/qutfcodec.cpp16
1 files changed, 13 insertions, 3 deletions
diff --git a/src/corelib/codecs/qutfcodec.cpp b/src/corelib/codecs/qutfcodec.cpp
index f1054ceb98..b4bc1583e6 100644
--- a/src/corelib/codecs/qutfcodec.cpp
+++ b/src/corelib/codecs/qutfcodec.cpp
@@ -53,6 +53,16 @@ enum { Endian = 0, Data = 1 };
static const uchar utf8bom[] = { 0xef, 0xbb, 0xbf };
#if defined(__SSE2__) && defined(QT_COMPILER_SUPPORTS_SSE2)
+static Q_ALWAYS_INLINE uint qBitScanReverse(unsigned v) Q_DECL_NOTHROW
+{
+ uint result = qCountLeadingZeroBits(v);
+ // Now Invert the result: clz will count *down* from the msb to the lsb, so the msb index is 31
+ // and the lsb index is 0. The result for _bit_scan_reverse is expected to be the index when
+ // counting up: msb index is 0 (because it starts there), and the lsb index is 31.
+ result ^= sizeof(unsigned) * 8 - 1;
+ return result;
+}
+
static inline bool simdEncodeAscii(uchar *&dst, const ushort *&nextAscii, const ushort *&src, const ushort *end)
{
// do sixteen characters at a time
@@ -81,9 +91,9 @@ static inline bool simdEncodeAscii(uchar *&dst, const ushort *&nextAscii, const
// find the next probable ASCII character
// we don't want to load 32 bytes again in this loop if we know there are non-ASCII
// characters still coming
- nextAscii = src + _bit_scan_reverse(n) + 1;
+ nextAscii = src + qBitScanReverse(n) + 1;
- n = _bit_scan_forward(n);
+ n = qCountTrailingZeroBits(n);
dst += n;
src += n;
return false;
@@ -132,7 +142,7 @@ static inline bool simdDecodeAscii(ushort *&dst, const uchar *&nextAscii, const
// find the next probable ASCII character
// we don't want to load 16 bytes again in this loop if we know there are non-ASCII
// characters still coming
- n = _bit_scan_reverse(n);
+ n = qBitScanReverse(n);
nextAscii = src + (n / BitSpacing) + 1;
return false;