Add cocotb_xls_test macro

Creates cocotb_xls_test macro that generates a file with the
timestamp specified in the rule definition. The macro is required to
generate the timestamp for Icarus Verilog smulation in Cocotb.

Internal-tag: [#46586]
Signed-off-by: Robert Winkler <rwinkler@antmicro.com>

xls/build_rules/cocotb_xls_test.bzl

@@ -0,0 +1,37 @@
+# Copyright 2023 The XLS Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("@rules_hdl//cocotb:cocotb.bzl", "cocotb_test")
+
+def cocotb_xls_test(**kwargs):
+    name = kwargs["name"]
+    top = kwargs["hdl_toplevel"]
+
+    if "timescale" in kwargs:
+        timescale = kwargs["timescale"]
+        timestamp_target = name + "-timescale"
+        timestamp_verilog = name + "_timescale.v"
+        native.genrule(
+            name = timestamp_target,
+            srcs = [],
+            cmd = "echo \\`timescale {}/{} > $@".format(
+                timescale["unit"],
+                timescale["precission"],
+            ),
+            outs = [timestamp_verilog],
+        )
+        kwargs["verilog_sources"].insert(0, timestamp_verilog)
+        kwargs.pop("timescale")
+
+    cocotb_test(**kwargs)

xls/examples/cocotb/BUILD

@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-load("@rules_hdl//cocotb:cocotb.bzl", "cocotb_test")
 load("@xls_pip_deps//:requirements.bzl", "requirement")
 load("//xls/build_rules:xls_build_defs.bzl", "xls_dslx_verilog")
+load("//xls/build_rules:cocotb_xls_test.bzl", "cocotb_xls_test")
 
 xls_dslx_verilog(
     name = "running_counter_verilog",
@@ -32,18 +32,21 @@ xls_dslx_verilog(
     verilog_file = "running_counter.v",
 )
 
-cocotb_test(
+cocotb_xls_test(
     name = "running_counter_cocotb",
     hdl_toplevel = "RunningCounter",
     hdl_toplevel_lang = "verilog",
     test_module = [
         "cocotb_running_counter.py",
     ],
     verilog_sources = [
-        "timescale.v",
         "dumpvcd.v",
         ":running_counter.v",
     ],
+    timescale = {
+        "unit": "1ns",
+        "precission": "1ps",
+    },
     deps = [
         requirement("cocotb"),
         requirement("cocotb_bus"),