Boost performance of QChar::isDigit

Make it inline; add fast checks for ascii digits;
add fallback function that uses the fastcall calling
convention.

On ia32, this change makes isDigit ~370x faster for
ascii digit characters, ~250x faster for non-digit
ascii characters, and ~1.5x faster for non-ascii
characters.

Note that this change is NOT binary compatible.

Also add an autotest with expected results from
before the optimization, to ensure that the
behavior is the same.

Change-Id: I718fadecda3f591d6f4c22374d8e476f4724fd83
Reviewed-on: http://codereview.qt-project.org/4902
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

src/corelib/tools/qchar.cpp

@@ -601,12 +601,19 @@ bool QChar::isLetterOrNumber() const
 }
 
 /*!
+    \fn bool QChar::isDigit() const
+
     Returns true if the character is a decimal digit
     (Number_DecimalDigit); otherwise returns false.
 */
-bool QChar::isDigit() const
+
+/*!
+    \internal
+    \overload
+*/
+bool QChar::isDigit(ushort ucs2)
 {
-    return (qGetProp(ucs)->category == Number_DecimalDigit);
+    return (qGetProp(ucs2)->category == Number_DecimalDigit);
 }
 
 /*!

src/corelib/tools/qchar.h

@@ -237,7 +237,8 @@ public:
     bool isLetter() const;
     bool isNumber() const;
     bool isLetterOrNumber() const;
-    bool isDigit() const;
+    inline bool isDigit() const
+    { return (ucs <= '9' && ucs >= '0') || (ucs > 127 && isDigit(ucs)); }
     bool isSymbol() const;
     inline bool isLower() const {
         return (ucs >= 'a' && ucs <= 'z')
@@ -315,6 +316,8 @@ public:
     static QString QT_FASTCALL decomposition(uint ucs4);
 
 private:
+    static bool QT_FASTCALL isDigit(ushort ucs2);
+
 #ifdef QT_NO_CAST_FROM_ASCII
     QChar(char c);
     QChar(uchar c);

tests/auto/corelib/tools/qchar/tst_qchar.cpp

@@ -73,6 +73,8 @@ private slots:
     void toLower();
     void toTitle();
     void toCaseFolded();
+    void isDigit_data();
+    void isDigit();
     void isPrint();
     void isUpper();
     void isLower();
@@ -223,6 +225,25 @@ void tst_QChar::toCaseFolded()
     QVERIFY(QChar::toCaseFolded((ushort)0xb5) == 0x3bc);
 }
 
+void tst_QChar::isDigit_data()
+{
+    QTest::addColumn<ushort>("ucs");
+    QTest::addColumn<bool>("expected");
+
+    for (ushort ucs = 0; ucs < 256; ++ucs) {
+        bool isDigit = (ucs <= '9' && ucs >= '0');
+        QString tag = QString::fromLatin1("0x%0").arg(QString::number(ucs, 16));
+        QTest::newRow(tag.toLatin1()) << ucs << isDigit;
+    }
+}
+
+void tst_QChar::isDigit()
+{
+    QFETCH(ushort, ucs);
+    QFETCH(bool, expected);
+    QCOMPARE(QChar(ucs).isDigit(), expected);
+}
+
 void tst_QChar::isPrint()
 {
     QVERIFY(QChar('A').isPrint());