fix expand as op (#48336)

* fix expand as op

* fix bug

paddle/phi/kernels/impl/expand_as_kernel_impl.h

@@ -120,24 +120,36 @@ void ExpandAsKernel(const Context& ctx,
                         target_rank,
                         MAX_RANK_SUPPORTED));
 
+  std::vector<int> real_target_shape = target_shape;
+  for (size_t i = 0; i < target_shape.size(); ++i) {
+    if (target_shape[i] == -1) {
+      if (y) {
+        if (y->IsInitialized()) {
+          real_target_shape = phi::vectorize<int>(y->dims());
+        }
+      }
+      break;
+    }
+  }
+
   switch (target_rank) {
     case 1:
-      ExpandAs<Context, T, 1>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 1>(ctx, x, real_target_shape, out);
       break;
     case 2:
-      ExpandAs<Context, T, 2>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 2>(ctx, x, real_target_shape, out);
       break;
     case 3:
-      ExpandAs<Context, T, 3>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 3>(ctx, x, real_target_shape, out);
       break;
     case 4:
-      ExpandAs<Context, T, 4>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 4>(ctx, x, real_target_shape, out);
       break;
     case 5:
-      ExpandAs<Context, T, 5>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 5>(ctx, x, real_target_shape, out);
       break;
     case 6:
-      ExpandAs<Context, T, 6>(ctx, x, target_shape, out);
+      ExpandAs<Context, T, 6>(ctx, x, real_target_shape, out);
       break;
   }
 }