repair bug of im2col

src/operators/math/im2col.cpp

@@ -73,9 +73,7 @@ class Im2ColFunctor<ColFormat::kCFO, CPU, T> {
     const int osize = col_height;
     const int isize = im_height;
     bool pad1 = padding[0] > 0;
-    bool pad2 =
-        (pad1 &&
-         (((isize - 2 * padding[0] + filter_height) % stride[0] == 0) ? 1 : 0));
+    bool pad2 = padding[1] > 0;
     int fill = isize % 2;
     if (stride[0] == 1 && filter_height == 3 && pad1 && pad2 &&
         dilation[0] == 1 && im_height > 2) {