Work around an apparent GCC optimiser bug accessing arrays beyond end

Accessing arrays beyond their end is known to cause problems in gcc
4.4 and 4.5. So don't try to be too smart in accessing m[0][index] but
instead access the array as it's meant to be.

Upstream bug: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43247#c10

Reviewed-by: Olivier Goffart

1 files changed, 40 insertions, 28 deletions

diff --git a/src/gui/math3d/qgenericmatrix.h b/src/gui/math3d/qgenericmatrix.h
index 3224ae2..f91bce7 100644
--- a/src/gui/math3d/qgenericmatrix.h
+++ b/src/gui/math3d/qgenericmatrix.h
@@ -198,52 +198,58 @@ Q_OUTOFLINE_TEMPLATE QGenericMatrix<M, N, T> QGenericMatrix<N, M, T>::transposed
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T>& QGenericMatrix<N, M, T>::operator+=(const QGenericMatrix<N, M, T>& other)
 {
-    for (int index = 0; index < N * M; ++index)
-        m[0][index] += other.m[0][index];
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            m[col][row] += other.m[col][row];
     return *this;
 }
 
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T>& QGenericMatrix<N, M, T>::operator-=(const QGenericMatrix<N, M, T>& other)
 {
-    for (int index = 0; index < N * M; ++index)
-        m[0][index] -= other.m[0][index];
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            m[col][row] -= other.m[col][row];
     return *this;
 }
 
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T>& QGenericMatrix<N, M, T>::operator*=(T factor)
 {
-    for (int index = 0; index < N * M; ++index)
-        m[0][index] *= factor;
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            m[col][row] *= factor;
     return *this;
 }
 
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE bool QGenericMatrix<N, M, T>::operator==(const QGenericMatrix<N, M, T>& other) const
 {
-    for (int index = 0; index < N * M; ++index) {
-        if (m[0][index] != other.m[0][index])
-            return false;
-    }
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)  {
+            if (m[col][row] != other.m[col][row])
+                return false;
+        }
     return true;
 }
 
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE bool QGenericMatrix<N, M, T>::operator!=(const QGenericMatrix<N, M, T>& other) const
 {
-    for (int index = 0; index < N * M; ++index) {
-        if (m[0][index] != other.m[0][index])
-            return true;
-    }
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col) {
+            if (m[col][row] != other.m[col][row])
+                return true;
+        }
     return false;
 }
 
 template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T>& QGenericMatrix<N, M, T>::operator/=(T divisor)
 {
-    for (int index = 0; index < N * M; ++index)
-        m[0][index] /= divisor;
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            m[col][row] /= divisor;
     return *this;
 }
 
@@ -251,8 +257,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator+(const QGenericMatrix<N, M, T>& m1, const QGenericMatrix<N, M, T>& m2)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = m1.m[0][index] + m2.m[0][index];
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = m1.m[col][row] + m2.m[col][row];
     return result;
 }
 
@@ -260,8 +267,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator-(const QGenericMatrix<N, M, T>& m1, const QGenericMatrix<N, M, T>& m2)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = m1.m[0][index] - m2.m[0][index];
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = m1.m[col][row] - m2.m[col][row];
     return result;
 }
 
@@ -284,8 +292,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator-(const QGenericMatrix<N, M, T>& matrix)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = -matrix.m[0][index];
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = -matrix.m[col][row];
     return result;
 }
 
@@ -293,8 +302,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator*(T factor, const QGenericMatrix<N, M, T>& matrix)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = matrix.m[0][index] * factor;
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = matrix.m[col][row] * factor;
     return result;
 }
 
@@ -302,8 +312,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator*(const QGenericMatrix<N, M, T>& matrix, T factor)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = matrix.m[0][index] * factor;
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = matrix.m[col][row] * factor;
     return result;
 }
 
@@ -311,8 +322,9 @@ template <int N, int M, typename T>
 Q_OUTOFLINE_TEMPLATE QGenericMatrix<N, M, T> operator/(const QGenericMatrix<N, M, T>& matrix, T divisor)
 {
     QGenericMatrix<N, M, T> result(1);
-    for (int index = 0; index < N * M; ++index)
-        result.m[0][index] = matrix.m[0][index] / divisor;
+    for (int row = 0; row < M; ++row)
+        for (int col = 0; col < N; ++col)
+            result.m[col][row] = matrix.m[col][row] / divisor;
     return result;
 }