Optimize QMatrix4x4::rotate() for 0, 90, 180, 270 degrees.

Reviewed-by: Sarah Smith

1 files changed, 17 insertions, 4 deletions

diff --git a/src/gui/math3d/qmatrix4x4.cpp b/src/gui/math3d/qmatrix4x4.cpp
index dc17eda50a..8fc439be6c 100644
--- a/src/gui/math3d/qmatrix4x4.cpp
+++ b/src/gui/math3d/qmatrix4x4.cpp
@@ -1010,11 +1010,24 @@ QMatrix4x4& QMatrix4x4::rotate(qreal angle, const QVector3D& vector)
 */
 QMatrix4x4& QMatrix4x4::rotate(qreal angle, qreal x, qreal y, qreal z)
 {
+    if (angle == 0.0f)
+        return *this;
     QMatrix4x4 m(1); // The "1" says to not load the identity.
-    qreal a = angle * M_PI / 180.0f;
-    qreal c = qCos(a);
-    qreal s = qSin(a);
-    qreal ic;
+    qreal c, s, ic;
+    if (angle == 90.0f || angle == -270.0f) {
+        s = 1.0f;
+        c = 0.0f;
+    } else if (angle == -90.0f || angle == 270.0f) {
+        s = -1.0f;
+        c = 0.0f;
+    } else if (angle == 180.0f || angle == -180.0f) {
+        s = 0.0f;
+        c = -1.0f;
+    } else {
+        qreal a = angle * M_PI / 180.0f;
+        c = qCos(a);
+        s = qSin(a);
+    }
     bool quick = false;
     if (x == 0.0f) {
         if (y == 0.0f) {