add trivial test

tests/Transforms/layout_propagation/BUILD

@@ -0,0 +1,10 @@
+load("//bazel:lit.bzl", "glob_lit_tests")
+
+package(default_applicable_licenses = ["@heir//:license"])
+
+glob_lit_tests(
+    name = "all_tests",
+    data = ["@heir//tests:test_utilities"],
+    driver = "@heir//tests:run_lit.sh",
+    test_file_exts = ["mlir"],
+)

tests/Transforms/layout_propagation/elementwise_add.mlir

@@ -0,0 +1,16 @@
+// RUN: heir-opt --layout-propagation %s | FileCheck %s
+
+!stensor = !secret.secret<tensor<32x32xi16>>
+#row_major = affine_map<(i, j) -> (32*i + j)>
+
+// Just test that the layout propagation pass runs, even though no layout
+// conversion ops are inserted.
+// CHECK-LABEL: elementwise_sum
+func.func @elementwise_sum(%arg0: !stensor, %arg1: !stensor) -> !stensor {
+  %0 = secret.generic ins(%arg0, %arg1: !stensor, !stensor) {
+  ^body(%pt_arg0: tensor<32x32xi16>, %pt_arg1: tensor<32x32xi16>):
+    %3 = arith.addi %pt_arg0, %pt_arg1: tensor<32x32xi16>
+    secret.yield %3 : tensor<32x32xi16>
+  } -> !stensor
+  return %0 : !stensor
+}