1 files changed, 18 insertions, 7 deletions

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 86dd80c65..52fcf3ee7 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -1530,10 +1530,16 @@ skip_dynamic_range_lvalue_expansion:;
 		current_scope[wire_en->str] = wire_en;
 		while (wire_en->simplify(true, false, false, 1, -1, false, false)) { }
 
-		std::vector<RTLIL::State> x_bit;
-		x_bit.push_back(RTLIL::State::Sx);
+		AstNode *check_defval;
+		if (type == AST_LIVE || type == AST_FAIR) {
+			check_defval = new AstNode(AST_REDUCE_BOOL, children[0]->clone());
+		} else {
+			std::vector<RTLIL::State> x_bit;
+			x_bit.push_back(RTLIL::State::Sx);
+			check_defval = mkconst_bits(x_bit, false);
+		}
 
-		AstNode *assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(x_bit, false));
+		AstNode *assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), check_defval);
 		assign_check->children[0]->str = id_check;
 		assign_check->children[0]->was_checked = true;
 
@@ -1546,9 +1552,13 @@ skip_dynamic_range_lvalue_expansion:;
 		default_signals->children.push_back(assign_en);
 		current_top_block->children.insert(current_top_block->children.begin(), default_signals);
 
-		assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), new AstNode(AST_REDUCE_BOOL, children[0]->clone()));
-		assign_check->children[0]->str = id_check;
-		assign_check->children[0]->was_checked = true;
+		if (type == AST_LIVE || type == AST_FAIR) {
+			assign_check = nullptr;
+		} else {
+			assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), new AstNode(AST_REDUCE_BOOL, children[0]->clone()));
+			assign_check->children[0]->str = id_check;
+			assign_check->children[0]->was_checked = true;
+		}
 
 		if (current_always == nullptr || current_always->type != AST_INITIAL) {
 			assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_int(1, false, 1));
@@ -1560,7 +1570,8 @@ skip_dynamic_range_lvalue_expansion:;
 		assign_en->children[0]->was_checked = true;
 
 		newNode = new AstNode(AST_BLOCK);
-		newNode->children.push_back(assign_check);
+		if (assign_check != nullptr)
+			newNode->children.push_back(assign_check);
 		newNode->children.push_back(assign_en);
 
 		AstNode *assertnode = new AstNode(type);