Add an SSE4.2 even simpler version of toLatin1

Use the new PCMPESTRM instruction (Parallel CoMPare Explicit-length
STRings with result in a Mask) which is added in SSE4.2 for
facilitating string operations. The "compare ranges" mode allows us to
search for characters outside the Latin 1 range and then use the
SSE4.1 PBLENDVB instruction to replace those with question marks.

Unlike previous SSE compare instructions, the PCMPxSTRx family allows
us to operate on unsigned 16-bit values. This saves us another
parallel add.

Reviewed-By: Samuel Rødal

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/auto/qstring/tst_qstring.cpp b/tests/auto/qstring/tst_qstring.cpp
index c19b168..b26121c 100644
--- a/tests/auto/qstring/tst_qstring.cpp
+++ b/tests/auto/qstring/tst_qstring.cpp
@@ -3475,6 +3475,10 @@ void tst_QString::toLatin1Roundtrip_data()
 
     static const ushort unicode6[] = { 0x180, 0x1ff, 0x8001, 0x8080, 0xfffc };
     QTest::newRow("non-latin1b") << QByteArray("?????") << QString::fromUtf16(unicode6, 5) << questionmarks;
+
+    static const ushort unicode7[] = { 'H', 'e', 'l', 'l', 'o', 0x100, 0x17f, 0x180, 0x8080, 0xfffc };
+    static const ushort unicode7q[] = { 'H', 'e', 'l', 'l', 'o', '?', '?', '?', '?', '?' };
+    QTest::newRow("mixed") << QByteArray("Hello?????") << QString::fromUtf16(unicode7, 10) << QString::fromUtf16(unicode7q, 10);
 }
 
 void tst_QString::toLatin1Roundtrip()