3 files changed, 26 insertions, 4 deletions

diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 5623541b2..29e175c15 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -194,6 +194,7 @@ AstNode::AstNode(AstNodeType type, AstNode *child1, AstNode *child2, AstNode *ch
 	is_logic = false;
 	is_signed = false;
 	is_string = false;
+	is_unsized = false;
 	was_checked = false;
 	range_valid = false;
 	range_swapped = false;
@@ -722,7 +723,7 @@ AstNode *AstNode::mkconst_int(uint32_t v, bool is_signed, int width)
 }
 
 // create an AST node for a constant (using a bit vector as value)
-AstNode *AstNode::mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed)
+AstNode *AstNode::mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed, bool is_unsized)
 {
 	AstNode *node = new AstNode(AST_CONSTANT);
 	node->is_signed = is_signed;
@@ -736,9 +737,15 @@ AstNode *AstNode::mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signe
 	node->range_valid = true;
 	node->range_left = node->bits.size()-1;
 	node->range_right = 0;
+	node->is_unsized = is_unsized;
 	return node;
 }
 
+AstNode *AstNode::mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed)
+{
+	return mkconst_bits(v, is_signed, false);
+}
+
 // create an AST node for a constant (using a string in bit vector form as value)
 AstNode *AstNode::mkconst_str(const std::vector<RTLIL::State> &v)
 {
@@ -775,6 +782,14 @@ bool AstNode::bits_only_01() const
 	return true;
 }
 
+RTLIL::Const AstNode::bitsAsUnsizedConst(int width)
+{
+	RTLIL::State extbit = bits.back();
+	while (width > int(bits.size()))
+		bits.push_back(extbit);
+	return RTLIL::Const(bits);
+}
+
 RTLIL::Const AstNode::bitsAsConst(int width, bool is_signed)
 {
 	std::vector<RTLIL::State> bits = this->bits;
diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 281cbe086..f90e683ad 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -173,7 +173,7 @@ namespace AST
 		// node content - most of it is unused in most node types
 		std::string str;
 		std::vector<RTLIL::State> bits;
-		bool is_input, is_output, is_reg, is_logic, is_signed, is_string, range_valid, range_swapped, was_checked;
+		bool is_input, is_output, is_reg, is_logic, is_signed, is_string, range_valid, range_swapped, was_checked, is_unsized;
 		int port_id, range_left, range_right;
 		uint32_t integer;
 		double realvalue;
@@ -262,6 +262,7 @@ namespace AST
 
 		// helper functions for creating AST nodes for constants
 		static AstNode *mkconst_int(uint32_t v, bool is_signed, int width = 32);
+		static AstNode *mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed, bool is_unsized);
 		static AstNode *mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed);
 		static AstNode *mkconst_str(const std::vector<RTLIL::State> &v);
 		static AstNode *mkconst_str(const std::string &str);
@@ -269,6 +270,7 @@ namespace AST
 		// helper function for creating sign-extended const objects
 		RTLIL::Const bitsAsConst(int width, bool is_signed);
 		RTLIL::Const bitsAsConst(int width = -1);
+		RTLIL::Const bitsAsUnsizedConst(int width);
 		RTLIL::Const asAttrConst();
 		RTLIL::Const asParaConst();
 		uint64_t asInt(bool is_signed);
diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index 379fed641..d9dfc17cc 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -963,8 +963,13 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 				detectSignWidth(width_hint, sign_hint);
 			is_signed = sign_hint;
 
-			if (type == AST_CONSTANT)
-				return RTLIL::SigSpec(bitsAsConst());
+			if (type == AST_CONSTANT) {
+				if (is_unsized) {
+					return RTLIL::SigSpec(bitsAsUnsizedConst(width_hint));
+				} else {
+					return RTLIL::SigSpec(bitsAsConst());
+				}
+			}
 
 			RTLIL::SigSpec sig = realAsConst(width_hint);
 			log_file_warning(filename, linenum, "converting real value %e to binary %s.\n", realvalue, log_signal(sig));