[firtool] Add -grand-central-instantiate-companion

Add an option that will cause Grand Central companion modules to not be
bound in (they are directly instantiated) and interfaces are no longer
emitted.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

test/Dialect/FIRRTL/SFCTests/GrandCentralInterfaces/InstantiateCompanionOnly.fir

@@ -0,0 +1,59 @@
+; RUN: firtool %s --grand-central-instantiate-companion | FileCheck %s --check-prefix CHECK
+
+circuit Foo : %[[
+  {
+    "class": "sifive.enterprise.grandcentral.GrandCentralView$SerializedViewAnnotation",
+    "name": "bar_view",
+    "companion": "~Foo|Companion",
+    "parent": "~Foo|Foo",
+    "view": {
+      "class": "sifive.enterprise.grandcentral.AugmentedBundleType",
+      "defName": "Bar_View",
+      "elements": [
+        {
+          "name": "bar_in",
+          "description": "bar in",
+          "tpe": {
+            "class": "sifive.enterprise.grandcentral.AugmentedGroundType",
+            "ref": {
+              "circuit": "Foo",
+              "module": "Foo",
+              "path": [],
+              "ref": "a",
+              "component": []
+            },
+            "tpe": {
+              "class": "sifive.enterprise.grandcentral.GrandCentralView$UnknownGroundType$"
+            }
+          }
+        }
+      ]
+    }
+  },
+  {
+    "class": "sifive.enterprise.grandcentral.ExtractGrandCentralAnnotation",
+    "directory": "Wire/firrtl/gct",
+    "filename": "Wire/firrtl/bindings.sv"
+  }
+]]
+  module Companion :
+    input clock: Clock
+    input a: UInt<1>
+
+    assert(clock, a, UInt<1>(1), "hello")
+
+  module Foo :
+    input clock: Clock
+
+    wire a: UInt<1>
+    a is invalid
+
+    inst companion of Companion
+    companion.clock <= clock
+    companion.a <= a
+
+    ; CHECK:     module Foo
+    ; CHECK-NOT: endmodule
+    ; CHECK-NOT:   emitted as a bind statement
+    ; CHECK:       Companion companion
+    ; CHECK:     endmodule

tools/firtool/firtool.cpp

@@ -303,6 +303,15 @@ static cl::opt<bool>
                         cl::desc("Disable the Grand Central passes"),
                         cl::init(false), cl::Hidden, cl::cat(mainCategory));
 
+static cl::opt<bool> grandCentralInstantiateCompanionOnly(
+    "grand-central-instantiate-companion",
+    cl::desc(
+        "Run Grand Central in a mode where the companion module is "
+        "instantiated and not bound in and the interface is dropped.  This is "
+        "intended for situations where there is useful assertion logic inside "
+        "the companion, but you don't care about the actual interface."),
+    cl::init(false), cl::Hidden, cl::cat(mainCategory));
+
 static cl::opt<bool> exportModuleHierarchy(
     "export-module-hierarchy",
     cl::desc("Export module and instance hierarchy as JSON"), cl::init(false),
@@ -753,7 +762,8 @@ static LogicalResult processBuffer(
   // certain black boxes should be placed.  Note: all Grand Central Taps related
   // collateral is resolved entirely by LowerAnnotations.
   if (!disableGrandCentral)
-    pm.addNestedPass<firrtl::CircuitOp>(firrtl::createGrandCentralPass());
+    pm.addNestedPass<firrtl::CircuitOp>(
+        firrtl::createGrandCentralPass(grandCentralInstantiateCompanionOnly));
 
   // Read black box source files into the IR.
   StringRef blackBoxRoot = blackBoxRootPath.empty()