From 41421f5dca3587172c870b548921331398a06c19 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sat, 18 Apr 2020 03:43:15 +0000
Subject: [PATCH] ast, rpc: record original name of $paramod\* as \hdlname
 attribute.

The $paramod name mangling is not invertible (the \ character, which
separates the module name from the parameters, is valid in the module
name itself), which does not stop people from trying to invert it.

This commit makes it easy to invert the name mangling by storing
the original name explicitly, and fixes the firrtl backend to use
the newly introduced attribute.
---
 backends/firrtl/firrtl.cc     | 13 ++-----------
 frontends/ast/ast.cc          |  3 +++
 frontends/rpc/rpc_frontend.cc |  2 ++
 3 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/backends/firrtl/firrtl.cc b/backends/firrtl/firrtl.cc
index fd7f20cc6..40d05a036 100644
--- a/backends/firrtl/firrtl.cc
+++ b/backends/firrtl/firrtl.cc
@@ -306,17 +306,8 @@ struct FirrtlWorker
 		// If this is a parameterized module, its parent module is encoded in the cell type
 		if (cell->type.begins_with("$paramod"))
 		{
-			std::string::iterator it;
-			for (it = cell_type.begin(); it < cell_type.end(); it++)
-			{
-				switch (*it) {
-					case '\\': /* FALL_THROUGH */
-					case '=': /* FALL_THROUGH */
-					case '\'': /* FALL_THROUGH */
-					case '$': instanceOf.append("_"); break;
-					default: instanceOf.append(1, *it); break;
-				}
-			}
+			log_assert(cell->has_attribute(ID::hdlname));
+			instanceOf = cell->get_string_attribute(ID::hdlname);
 		}
 		else
 		{
diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 245a53611..de741a506 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -1565,6 +1565,9 @@ std::string AstModule::derive_common(RTLIL::Design *design, const dict<RTLIL::Id
 	rewritten.reserve(GetSize(parameters));
 
 	AstNode *new_ast = ast->clone();
+	if (!new_ast->attributes.count(ID::hdlname))
+		new_ast->attributes[ID::hdlname] = AstNode::mkconst_str(stripped_name);
+
 	para_counter = 0;
 	for (auto child : new_ast->children) {
 		if (child->type != AST_PARAMETER)
diff --git a/frontends/rpc/rpc_frontend.cc b/frontends/rpc/rpc_frontend.cc
index a23f7548e..46ee6a733 100644
--- a/frontends/rpc/rpc_frontend.cc
+++ b/frontends/rpc/rpc_frontend.cc
@@ -217,6 +217,8 @@ struct RpcModule : RTLIL::Module {
 				module.second->name = mangled_name;
 				module.second->design = design;
 				module.second->attributes.erase(ID::top);
+				if (!module.second->has_attribute(ID::hdlname))
+					module.second->set_string_attribute(ID::hdlname, module.first.str());
 				design->modules_[mangled_name] = module.second;
 				derived_design->modules_.erase(module.first);
 			}