Fix reshape op. (#10253)

paddle/fluid/operators/reshape_op.h

@@ -93,8 +93,14 @@ class ReshapeOp : public framework::OperatorWithKernel {
 
     if (unk_dim_idx != -1) {
       output_shape[unk_dim_idx] = -in_size / capacity;
-      PADDLE_ENFORCE_EQ(output_shape[unk_dim_idx] * capacity, -in_size,
-                        "Invalid shape is given.");
+      // in_size < 0 and is un-determinate in compile time, skip the check,
+      // for example, in_dims = [-1, 8, 1, 1], shape = [-1, 3, 8],
+      // capacity = -24, in_size = -8, output_shape[0] = 0
+      // the following check will fail.
+      if (in_size > 0) {
+        PADDLE_ENFORCE_EQ(output_shape[unk_dim_idx] * capacity, -in_size,
+                          "Invalid shape is given.");
+      }
     } else {
       PADDLE_ENFORCE_EQ(capacity, in_size, "Invalid shape is given.");
     }