Speed-up parsing of SVG path data.

Instead of using operations that shuffle the array of numbers, just
use pointer to iterate the numbers. This reduced the amount of
memory operations during the parsing.

In addition, parse the numbers to QVarLengthArray instead of QVector.
This works well because usually a path element is typically followed by
a short list of numbers.

Loading tiger.svg (tests/benchmarks/qsvgrenderer) is now 8% faster,
mostly due to the time spent in parsePathDataFast is reduced from
26.1 millions instructions to just 20.5 millions (27% speed-up).

Reviewed-by: Kim

1 files changed, 127 insertions, 117 deletions

diff --git a/src/svg/qsvghandler.cpp b/src/svg/qsvghandler.cpp
index 27de011..9683efd 100644
--- a/src/svg/qsvghandler.cpp
+++ b/src/svg/qsvghandler.cpp
@@ -1414,24 +1414,29 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
         QChar pathElem = *str;
         ++str;
         QChar endc = *end;
-        *const_cast<QChar *>(end) = 0; // parseNumbersList requires 0-termination that QStringRef cannot guarantee
-        QVector<qreal> arg = parseNumbersList(str);
+        *const_cast<QChar *>(end) = 0; // parseNumbersArray requires 0-termination that QStringRef cannot guarantee
+        QVarLengthArray<qreal, 8> arg;
+        parseNumbersArray(str, arg);
         *const_cast<QChar *>(end) = endc;
         if (pathElem == QLatin1Char('z') || pathElem == QLatin1Char('Z'))
             arg.append(0);//dummy
-        while (!arg.isEmpty()) {
+        const qreal *num = arg.constData();
+        int count = arg.count();
+        while (count > 0) {
             qreal offsetX = x;        // correction offsets
             qreal offsetY = y;        // for relative commands
             switch (pathElem.unicode()) {
             case 'm': {
-                if (arg.count() < 2) {
-                    arg.pop_front();
+                if (count < 2) {
+                    num++;
+                    count--;
                     break;
                 }
-                x = x0 = arg[0] + offsetX;
-                y = y0 = arg[1] + offsetY;
+                x = x0 = num[0] + offsetX;
+                y = y0 = num[1] + offsetY;
+                num += 2;
+                count -= 2;
                 path.moveTo(x0, y0);
-                arg.pop_front(); arg.pop_front();
 
                  // As per 1.2  spec 8.3.2 The "moveto" commands
                  // If a 'moveto' is followed by multiple pairs of coordinates without explicit commands,
@@ -1440,15 +1445,16 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
             }
                 break;
             case 'M': {
-                if (arg.count() < 2) {
-                    arg.pop_front();
+                if (count < 2) {
+                    num++;
+                    count--;
                     break;
                 }
-                x = x0 = arg[0];
-                y = y0 = arg[1];
-
+                x = x0 = num[0];
+                y = y0 = num[1];
+                num += 2;
+                count -= 2;
                 path.moveTo(x0, y0);
-                arg.pop_front(); arg.pop_front();
 
                 // As per 1.2  spec 8.3.2 The "moveto" commands
                 // If a 'moveto' is followed by multiple pairs of coordinates without explicit commands,
@@ -1460,96 +1466,104 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
             case 'Z': {
                 x = x0;
                 y = y0;
+                count--; // skip dummy
+                num++;
                 path.closeSubpath();
-                arg.pop_front();//pop dummy
             }
                 break;
             case 'l': {
-                if (arg.count() < 2) {
-                    arg.pop_front();
+                if (count < 2) {
+                    num++;
+                    count--;
                     break;
                 }
-                x = arg.front() + offsetX;
-                arg.pop_front();
-                y = arg.front() + offsetY;
-                arg.pop_front();
+                x = x0 = num[0] + offsetX;
+                y = y0 = num[1] + offsetY;
+                num += 2;
+                count -= 2;
                 path.lineTo(x, y);
 
             }
                 break;
             case 'L': {
-                if (arg.count() < 2) {
-                    arg.pop_front();
+                if (count < 2) {
+                    num++;
+                    count--;
                     break;
                 }
-                x = arg.front(); arg.pop_front();
-                y = arg.front(); arg.pop_front();
+                x = x0 = num[0];
+                y = y0 = num[1];
+                num += 2;
+                count -= 2;
                 path.lineTo(x, y);
             }
                 break;
             case 'h': {
-                x = arg.front() + offsetX; arg.pop_front();
+                x = num[0] + offsetX;
+                num++;
+                count--;
                 path.lineTo(x, y);
             }
                 break;
             case 'H': {
-                x = arg[0];
+                x = num[0];
+                num++;
+                count--;
                 path.lineTo(x, y);
-                arg.pop_front();
             }
                 break;
             case 'v': {
-                y = arg[0] + offsetY;
+                y = num[0] + offsetY;
+                num++;
+                count--;
                 path.lineTo(x, y);
-                arg.pop_front();
             }
                 break;
             case 'V': {
-                y = arg[0];
+                y = num[0];
+                num++;
+                count--;
                 path.lineTo(x, y);
-                arg.pop_front();
             }
                 break;
             case 'c': {
-                if (arg.count() < 6) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 6) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF c1(arg[0]+offsetX, arg[1]+offsetY);
-                QPointF c2(arg[2]+offsetX, arg[3]+offsetY);
-                QPointF e(arg[4]+offsetX, arg[5]+offsetY);
+                QPointF c1(num[0] + offsetX, num[1] + offsetY);
+                QPointF c2(num[2] + offsetX, num[3] + offsetY);
+                QPointF e(num[4] + offsetX, num[5] + offsetY);
+                num += 6;
+                count -= 6;
                 path.cubicTo(c1, c2, e);
                 ctrlPt = c2;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'C': {
-                if (arg.count() < 6) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 6) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF c1(arg[0], arg[1]);
-                QPointF c2(arg[2], arg[3]);
-                QPointF e(arg[4], arg[5]);
+                QPointF c1(num[0], num[1]);
+                QPointF c2(num[2], num[3]);
+                QPointF e(num[4], num[5]);
+                num += 6;
+                count -= 6;
                 path.cubicTo(c1, c2, e);
                 ctrlPt = c2;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 's': {
-                if (arg.count() < 4) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 4) {
+                    num += count;
+                    count = 0;
                     break;
                 }
                 QPointF c1;
@@ -1558,20 +1572,20 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
                     c1 = QPointF(2*x-ctrlPt.x(), 2*y-ctrlPt.y());
                 else
                     c1 = QPointF(x, y);
-                QPointF c2(arg[0]+offsetX, arg[1]+offsetY);
-                QPointF e(arg[2]+offsetX, arg[3]+offsetY);
+                QPointF c2(num[0] + offsetX, num[1] + offsetY);
+                QPointF e(num[2] + offsetX, num[3] + offsetY);
+                num += 4;
+                count -= 4;
                 path.cubicTo(c1, c2, e);
                 ctrlPt = c2;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'S': {
-                if (arg.count() < 4) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 4) {
+                    num += count;
+                    count = 0;
                     break;
                 }
                 QPointF c1;
@@ -1580,55 +1594,57 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
                     c1 = QPointF(2*x-ctrlPt.x(), 2*y-ctrlPt.y());
                 else
                     c1 = QPointF(x, y);
-                QPointF c2(arg[0], arg[1]);
-                QPointF e(arg[2], arg[3]);
+                QPointF c2(num[0], num[1]);
+                QPointF e(num[2], num[3]);
+                num += 4;
+                count -= 4;
                 path.cubicTo(c1, c2, e);
                 ctrlPt = c2;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'q': {
-                if (arg.count() < 4) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 4) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF c(arg[0]+offsetX, arg[1]+offsetY);
-                QPointF e(arg[2]+offsetX, arg[3]+offsetY);
+                QPointF c(num[0] + offsetX, num[1] + offsetY);
+                QPointF e(num[2] + offsetX, num[3] + offsetY);
+                num += 4;
+                count -= 4;
                 path.quadTo(c, e);
                 ctrlPt = c;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'Q': {
-                if (arg.count() < 4) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 4) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF c(arg[0], arg[1]);
-                QPointF e(arg[2], arg[3]);
+                QPointF c(num[0], num[1]);
+                QPointF e(num[2], num[3]);
+                num += 4;
+                count -= 4;
                 path.quadTo(c, e);
                 ctrlPt = c;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 't': {
-                if (arg.count() < 2) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 2) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF e(arg[0]+offsetX, arg[1]+offsetY);
+                QPointF e(num[0] + offsetX, num[1] + offsetY);
+                num += 2;
+                count -= 2;
                 QPointF c;
                 if (lastMode == 'q' || lastMode == 'Q' ||
                     lastMode == 't' || lastMode == 'T')
@@ -1639,16 +1655,17 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
                 ctrlPt = c;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'T': {
-                if (arg.count() < 2) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 2) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                QPointF e(arg[0], arg[1]);
+                QPointF e(num[0], num[1]);
+                num += 2;
+                count -= 2;
                 QPointF c;
                 if (lastMode == 'q' || lastMode == 'Q' ||
                     lastMode == 't' || lastMode == 'T')
@@ -1659,22 +1676,22 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
                 ctrlPt = c;
                 x = e.x();
                 y = e.y();
-                arg.pop_front(); arg.pop_front();
                 break;
             }
             case 'a': {
-                if (arg.count() < 7) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 7) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                qreal rx = arg[0];
-                qreal ry = arg[1];
-                qreal xAxisRotation = arg[2];
-                qreal largeArcFlag  = arg[3];
-                qreal sweepFlag = arg[4];
-                qreal ex = arg[5] + offsetX;
-                qreal ey = arg[6] + offsetY;
+                qreal rx = (*num++);
+                qreal ry = (*num++);
+                qreal xAxisRotation = (*num++);
+                qreal largeArcFlag  = (*num++);
+                qreal sweepFlag = (*num++);
+                qreal ex = (*num++) + offsetX;
+                qreal ey = (*num++) + offsetY;
+                count -= 7;
                 qreal curx = x;
                 qreal cury = y;
                 pathArc(path, rx, ry, xAxisRotation, int(largeArcFlag),
@@ -1682,36 +1699,29 @@ static bool parsePathDataFast(const QStringRef &dataStr, QPainterPath &path)
 
                 x = ex;
                 y = ey;
-
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front();
             }
                 break;
             case 'A': {
-                if (arg.count() < 7) {
-                    while (arg.count())
-                        arg.pop_front();
+                if (count < 7) {
+                    num += count;
+                    count = 0;
                     break;
                 }
-                qreal rx = arg[0];
-                qreal ry = arg[1];
-                qreal xAxisRotation = arg[2];
-                qreal largeArcFlag  = arg[3];
-                qreal sweepFlag = arg[4];
-                qreal ex = arg[5];
-                qreal ey = arg[6];
+                qreal rx = (*num++);
+                qreal ry = (*num++);
+                qreal xAxisRotation = (*num++);
+                qreal largeArcFlag  = (*num++);
+                qreal sweepFlag = (*num++);
+                qreal ex = (*num++);
+                qreal ey = (*num++);
+                count -= 7;
                 qreal curx = x;
                 qreal cury = y;
                 pathArc(path, rx, ry, xAxisRotation, int(largeArcFlag),
                         int(sweepFlag), ex, ey, curx, cury);
+
                 x = ex;
                 y = ey;
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front(); arg.pop_front();
-                arg.pop_front();
             }
                 break;
             default: