conv shift: fix return before syncthreads

paddle/operators/conv_shift_op.cu

@@ -62,19 +62,19 @@ __global__ void ConvShiftForward(const T *x, const T *y, T *out, int x_width,
   if (tx < num_x) {
     int load_i = (i - y_half_width + x_width) % x_width;
     sx[tx] = x[k * x_width + load_i];
-  } else {
-    return;
   }
   __syncthreads();
 
-  // Compute dot product of sx[tx:tx + y_width] and sy.
-  T sum = 0;
-  for (int j = 0; j < y_width; ++j) {
-    sum += sx[tx + j] * sy[j];
-  }
+  if (tx < num_x) {
+    // Compute dot product of sx[tx:tx + y_width] and sy.
+    T sum = 0;
+    for (int j = 0; j < y_width; ++j) {
+      sum += sx[tx + j] * sy[j];
+    }
 
-  // Save to out[k, i].
-  out[k * x_width + i] = sum;
+    // Save to out[k, i].
+    out[k * x_width + i] = sum;
+  }
 }
 
 // Compute x gradient - initial naive implementation with atomic add.