conv shift: fix return before syncthreads

paddle/operators/conv_shift_op.cu

@@ -62,11 +62,10 @@ __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();
 
+  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) {
@@ -75,6 +74,7 @@ __global__ void ConvShiftForward(const T *x, const T *y, T *out, int x_width,
 
     // Save to out[k, i].
     out[k * x_width + i] = sum;
+  }
 }
 
 // Compute x gradient - initial naive implementation with atomic add.