yosys: avoid resynthesis on ORFS upgrade when yosys doesn't change

This still works:

bazel run //sram:sdq_17x64_synth $(pwd)/tmp open_synth

Signed-off-by: Øyvind Harboe <[email protected]>

openroad.bzl

@@ -154,14 +154,13 @@ def yosys_environment(ctx):
 def config_environment(config):
     return {"DESIGN_CONFIG": config.path}
 
-def flow_inputs(ctx):
+def flow_inputs(ctx, openroad = True):
     return depset(
         [
             ctx.executable._klayout,
             ctx.executable._make,
-            ctx.executable._openroad,
             ctx.file._makefile,
-        ] +
+        ] + ([ctx.executable._openroad] if openroad else []) +
         ctx.files._ruby +
         ctx.files._ruby_dynamic +
         ctx.files._tcl +
@@ -637,7 +636,7 @@ def _yosys_impl(ctx):
             ctx.files.verilog_files +
             ctx.files.extra_configs,
             transitive = [
-                flow_inputs(ctx),
+                flow_inputs(ctx, openroad = False),
                 yosys_inputs(ctx),
                 data_inputs(ctx),
                 pdk_inputs(ctx),
@@ -678,7 +677,7 @@ def _yosys_impl(ctx):
             [canon_output, config] +
             ctx.files.extra_configs,
             transitive = [
-                flow_inputs(ctx),
+                flow_inputs(ctx, openroad = False),
                 yosys_inputs(ctx),
                 data_inputs(ctx),
                 pdk_inputs(ctx),
@@ -688,7 +687,22 @@ def _yosys_impl(ctx):
         outputs = synth_outputs + synth_logs,
     )
 
-    outputs = [canon_output] + synth_outputs
+    # Dummy action to make sure that the flow environment is available to
+    # bazel run foo_synth without causing resynthesis when upgrading
+    # ORFS where yosys did not change, saves many hours of synthesis
+    dummy_output = _declare_artifact(ctx, "results", "dummy.txt")
+    ctx.actions.run_shell(
+        command = "touch " + dummy_output.path,
+        env = flow_environment(ctx),
+        inputs = depset(
+            transitive = [
+                flow_inputs(ctx),
+            ],
+        ),
+        outputs = [dummy_output],
+    )
+
+    outputs = [canon_output] + synth_outputs + [dummy_output]
 
     config_short = _declare_artifact(ctx, "results", "1_synth.short.mk")
     ctx.actions.write(