[XLA] Produce fake args using one computation, not N.

This is much faster to compile.

PiperOrigin-RevId: 207577415

tensorflow/compiler/xla/client/lib/testing.cc

@@ -98,14 +98,13 @@ std::vector<std::unique_ptr<GlobalData>> MakeFakeArgumentsOrDie(
       << "Computation should have progran shape.";
   auto program_shape = computation.proto().program_shape();
 
-  // For every (unbound) parameter that the computation wants, we manufacture
-  // some arbitrary data so that we can invoke the computation.
-  std::vector<std::unique_ptr<GlobalData>> fake_arguments;
-  for (const Shape& parameter : program_shape.parameters()) {
-    fake_arguments.push_back(MakeFakeDataOrDie(parameter, client));
-  }
-
-  return fake_arguments;
+  // Create and run a program which produces a tuple with one element per
+  // parameter, then return the tuple's constituent buffers.
+  std::vector<Shape> param_shapes(program_shape.parameters().begin(),
+                                  program_shape.parameters().end());
+  auto fake_input_tuple =
+      MakeFakeDataOrDie(ShapeUtil::MakeTupleShape(param_shapes), client);
+  return client->DeconstructTuple(*fake_input_tuple).ValueOrDie();
 }
 
 }  // namespace xla