Add a rust-cosim flag

tools/hdl.bzl

@@ -125,6 +125,8 @@ def _hdl_unit_impl(ctx: AnalysisContext) -> list[Provider]:
         cmd.add("--output", out_run_py.as_output())
         if ctx.attrs.simulator:
             cmd.add("--simulator", ctx.attrs.simulator)
+        if ctx.attrs.rust_cosim:
+            cmd.add("--rust-cosim", ctx.attrs.rust_cosim)
         ctx.actions.run(cmd, category="vunit")
 
         # Left here as an example of how to put the vunit_out
@@ -225,6 +227,11 @@ vhdl_unit = rule(
             doc="nvc or ghdl",
             default="nvc",
         ),
+        "rust_cosim": attrs.option(
+            attrs.string(),
+            doc="Path to Rust cosim library (sets both GPI_USERS env var and NVC --load flag)",
+            default=None,
+        ),
         "_toolchain": attrs.toolchain_dep(
             doc="Use system python toolchain for running VUnit",
             default="toolchains//:python",
@@ -266,4 +273,4 @@ def third_party(**kwargs):
 # are dropped from synthesis and simulation outputs
 def black_box(**kwargs):
     kwargs.update({"is_black_box": True})
-    vhdl_unit(**kwargs)
+    vhdl_unit(**kwargs)

tools/vunit_gen/templates/run_py.jinja2

@@ -74,8 +74,16 @@ vu.add_verification_components()
 vu.set_sim_option("disable_ieee_warnings", True)
 {% if simulator == "nvc" %}
 # Dump arrays of records, may have a perf penalty
-vu.set_sim_option("nvc.sim_flags", ["--dump-arrays"])
+nvc_sim_flags = ["--dump-arrays"]
+{% if rust_cosim %}
+# Load Rust cosimulation library
+nvc_sim_flags.append("--load")
+nvc_sim_flags.append("{{rust_cosim}}")
+# Set GPI_USERS environment variable for Rust cosimulation
+os.environ["GPI_USERS"] = "{{rust_cosim}}"
+{% endif %}
+vu.set_sim_option("nvc.sim_flags", nvc_sim_flags)
 vu.set_sim_option("nvc.global_flags", ["--ignore-time"])
 {% endif %}
 # Run vunit function
-vu.main()
+vu.main()

tools/vunit_gen/vunit_gen_cli.py

@@ -15,6 +15,7 @@
 )
 parser.add_argument("--output", dest="output", help="Explicit output list")
 parser.add_argument("--simulator", dest="simulator", default="", help="specify simulator name (ghdl or nvc)")
+parser.add_argument("--rust-cosim", dest="rust_cosim", default="", help="Path to Rust cosim library")
 
 args = parser.parse_args()
 
@@ -72,6 +73,7 @@ def main():
         simulator=args.simulator,
         vhdl_standard=inputs.get("vhdl_std"),
         codec_packages=[],
+        rust_cosim=args.rust_cosim,
         # vunit_out=args.vunit_out,
     )
     with open(args.output, mode="w", encoding="utf-8") as message: