[MooreToCore][NFC] Fix the visibility of hw.module. (#7396)

Author: Hailong Sun

lib/Conversion/MooreToCore/MooreToCore.cpp

@@ -103,10 +103,14 @@ struct SVModuleOpConversion : public OpConversionPattern<SVModuleOp> {
     auto outputOp = op.getOutputOp();
     rewriter.setInsertionPoint(op);
 
-    // Create the hw.module to replace svmoduleOp
+    // Create the hw.module to replace moore.module
     auto hwModuleOp =
         rewriter.create<hw::HWModuleOp>(op.getLoc(), op.getSymNameAttr(),
                                         getModulePortInfo(*typeConverter, op));
+    // Make hw.module have the same visibility as the moore.module.
+    // The entry/top level module is public, otherwise is private.
+    SymbolTable::setSymbolVisibility(hwModuleOp,
+                                     SymbolTable::getSymbolVisibility(op));
     rewriter.eraseBlock(hwModuleOp.getBodyBlock());
     rewriter.inlineRegionBefore(op.getBodyRegion(), hwModuleOp.getBodyRegion(),
                                 hwModuleOp.getBodyRegion().end());

test/Conversion/MooreToCore/basic.mlir

@@ -201,8 +201,8 @@ moore.module @InstanceNull() {
   moore.output
 }
 
-// CHECK-LABEL: hw.module @Null() {
-moore.module @Null() {
+// CHECK-LABEL: hw.module private @Null() {
+moore.module private @Null() {
 
   // CHECK-NEXT: hw.output
   moore.output
@@ -222,10 +222,10 @@ moore.module @Top(in %arg0 : !moore.l1, in %arg1 : !moore.l1, out out0 : !moore.
   moore.output %inst_1.c : !moore.l1
 }
 
-// CHECK-LABEL: hw.module @SubModule_0(in
+// CHECK-LABEL: hw.module private @SubModule_0(in
 // CHECK-SAME: %[[V0:.*]] : i1, in
 // CHECK-SAME: %[[V1:.*]] : i1, out c : i1) {
-moore.module @SubModule_0(in %a : !moore.l1, in %b : !moore.l1, out c : !moore.l1) {
+moore.module private @SubModule_0(in %a : !moore.l1, in %b : !moore.l1, out c : !moore.l1) {
   // CHECK-NEXT: %[[V2:.*]] = comb.and %[[V0]], %[[V1]] : i1
   %0 = moore.and %a, %b : !moore.l1