Generalise structs and add support for packed unions.

8 files changed, 209 insertions, 59 deletions

diff --git a/README.md b/README.md
index 3058220e7..770c62459 100644
--- a/README.md
+++ b/README.md
@@ -556,7 +556,7 @@ from SystemVerilog:
 - enums are supported (including inside packages)
 	- but are currently not strongly typed
 
-- structs are supported
+- packed structs and unions are supported.
 
 - SystemVerilog interfaces (SVIs) are supported. Modports for specifying whether
   ports are inputs or outputs are supported.
diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 2c16de0a4..03fd272da 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -172,6 +172,7 @@ std::string AST::type2str(AstNodeType type)
 	X(AST_WIRETYPE)
 	X(AST_TYPEDEF)
 	X(AST_STRUCT)
+	X(AST_UNION)
 	X(AST_STRUCT_ITEM)
 #undef X
 	default:
diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 29bd1b84d..6d556fae2 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -158,6 +158,7 @@ namespace AST
 		AST_WIRETYPE,
 		AST_TYPEDEF,
 		AST_STRUCT,
+		AST_UNION,
 		AST_STRUCT_ITEM
 	};
 
diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index a57333314..83f34c9e1 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -992,6 +992,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 	case AST_MODPORTMEMBER:
 	case AST_TYPEDEF:
 	case AST_STRUCT:
+	case AST_UNION:
 		break;
 	case AST_INTERFACEPORT: {
 		// If a port in a module with unknown type is found, mark it with the attribute 'is_interface'
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index ce435c26b..e8ac4b2f2 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -250,6 +250,97 @@ static AstNode *make_range(int left, int right, bool is_signed = false)
 	return range;
 }
 
+int size_packed_struct(AstNode *snode, int base_offset)
+{
+	// Struct members will be laid out in the structure contiguously from left to right.
+	// Union members all have zero offset from the start of the union.
+	// Determine total packed size and assign offsets.  Store these in the member node.
+	bool is_union = (snode->type == AST_UNION);
+	int offset = 0;
+	int packed_width = -1;
+	// examine members from last to first
+	for (auto it = snode->children.rbegin(); it != snode->children.rend(); ++it) {
+		auto node = *it;
+		int width;
+		if (node->type == AST_STRUCT || node->type == AST_UNION) {
+			// embedded struct or union
+			width = size_packed_struct(node, base_offset + offset);
+		}
+		else {
+			log_assert(node->type == AST_STRUCT_ITEM);
+			if (node->children.size() == 1 && node->children[0]->type == AST_RANGE) {
+				auto rnode = node->children[0];
+				width = (rnode->range_swapped ? rnode->range_right - rnode->range_left :
+								rnode->range_left - rnode->range_right) + 1;
+				// range nodes are now redundant
+				node->children.clear();
+			}
+			else if (node->range_left < 0) {
+				// 1 bit signal: bit, logic or reg
+				width = 1;
+			}
+			else {
+				// already resolved and compacted
+				width = node->range_left - node->range_right + 1;
+			}
+			if (is_union) {
+				node->range_right = base_offset;
+				node->range_left = base_offset + width - 1;
+			}
+			else {
+				node->range_right = base_offset + offset;
+				node->range_left = base_offset + offset + width - 1;
+			}
+			node->range_valid = true;
+		}
+		if (is_union) {
+			// check that all members have the same size
+			if (packed_width == -1) {
+				// first member
+				packed_width = width;
+			}
+			else {
+				if (packed_width != width) {
+
+					log_file_error(node->filename, node->location.first_line, "member %s of a packed union has %d bits, expecting %d\n", node->str.c_str(), width, packed_width);
+				}
+			}
+		}
+		else {
+			offset += width;
+		}
+	}
+	return (is_union ? packed_width : offset);
+}
+
+static void add_members_to_scope(AstNode *snode, std::string name)
+{
+	// add all the members in a struct or union to local scope
+	// in case later referenced in assignments
+	log_assert(snode->type==AST_STRUCT || snode->type==AST_UNION);
+	for (auto *node : snode->children) {
+		if (node->type != AST_STRUCT_ITEM) {
+			// embedded struct or union
+			add_members_to_scope(node, name + "." + node->str);
+		}
+		else {
+			auto member_name = name + "." + node->str;
+			current_scope[member_name] = node;
+		}
+	}
+}
+
+static int get_max_offset(AstNode *node)
+{
+	// get the width from the MS member in the struct
+	// as members are laid out from left to right in the packed wire
+	log_assert(node->type==AST_STRUCT || node->type==AST_UNION);
+	while (node->type != AST_STRUCT_ITEM) {
+		node = node->children[0];
+	}
+	return node->range_left;
+}
+
 static AstNode *make_packed_struct(AstNode *template_node, std::string &name)
 {
 	// create a wire for the packed struct
@@ -257,18 +348,14 @@ static AstNode *make_packed_struct(AstNode *template_node, std::string &name)
 	wnode->str = name;
 	wnode->is_logic = true;
 	wnode->range_valid = true;
-	// get the width from the MS member in the template
-	// as members are laid out from left to right
-	int offset = template_node->children[0]->range_left;
+	wnode->is_signed = template_node->is_signed;
+	int offset = get_max_offset(template_node);
 	auto range = make_range(offset, 0);
 	wnode->children.push_back(range);
 	// make sure this node is the one in scope for this name
 	current_scope[name] = wnode;
-	// add members to scope
-	for (auto *node : template_node->children) {
-		auto member_name = name + "." + node->str;
-		current_scope[member_name] = node;
-	}
+	// add all the struct members to scope under the wire's name
+	add_members_to_scope(template_node, name);
 	return wnode;
 }
 
@@ -672,46 +759,25 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		break;
 
 	case AST_STRUCT:
-		//log("STRUCT %d %d %d\n", stage, basic_prep, in_param);
+	case AST_UNION:
 		if (!basic_prep) {
-			//dumpAst(NULL, "1> ");
 			for (auto *node : children) {
 				// resolve any ranges
 				while (!node->basic_prep && node->simplify(true, false, false, stage, -1, false, false)) {
 					did_something = true;
 				}
 			}
-			basic_prep = true;
-			// The members will be laid out in the structure contiguously from left to right.
-			// Determine total packed size and assign offsets.  Store these in the member node.
-			// dumpAst(NULL, "2> ");
-			int offset = 0;
-			for (auto it = children.rbegin(); it != children.rend(); ++it) {
-				auto node = *it;
-				if (is_signed)
-					node->is_signed = true;
-				int width;
-				if (node->children.size() == 1 && node->children[0]->type == AST_RANGE) {
-					auto rnode = node->children[0];
-					width = (rnode->range_swapped ? rnode->range_right - rnode->range_left :
-									rnode->range_left - rnode->range_right) + 1;
-					// range nodes are now redundant
-					node->children.clear();
-				}
-				else {
-					width = 1;
-				}
-				node->range_right = offset;
-				node->range_left = offset + width - 1;
-				node->range_valid = true;
-				offset += width;
-			}
-			if (!str.empty()) {
-				// instance rather than just a type in a typedef
-				// so add a wire for the packed structure
+			// determine member offsets and widths
+			size_packed_struct(this, 0);
+
+			// instance rather than just a type in a typedef or outer struct?
+			if (!str.empty() && str[0] == '\\') {
+				// instance so add a wire for the packed structure
 				auto wnode = make_packed_struct(this, str);
+				log_assert(current_ast_mod);
 				current_ast_mod->children.push_back(wnode);
 			}
+			basic_prep = true;
 		}
 		break;
 
@@ -1036,7 +1102,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 	if (type == AST_TYPEDEF) {
 		log_assert(children.size() == 1);
 		auto type_node = children[0];
-		log_assert(type_node->type == AST_WIRE || type_node->type == AST_MEMORY || type_node->type == AST_STRUCT);
+		log_assert(type_node->type == AST_WIRE || type_node->type == AST_MEMORY || type_node->type == AST_STRUCT || type_node->type == AST_UNION);
 		while (type_node->simplify(const_fold, at_zero, in_lvalue, stage, width_hint, sign_hint, in_param)) {
 			did_something = true;
 		}
@@ -1061,7 +1127,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			// Ensure typedef itself is fully simplified
 			while (template_node->simplify(const_fold, at_zero, in_lvalue, stage, width_hint, sign_hint, in_param)) {};
 
-			if (template_node->type == AST_STRUCT) {
+			if (template_node->type == AST_STRUCT || template_node->type == AST_UNION) {
 				// replace with wire representing the packed structure
 				newNode = make_packed_struct(template_node, str);
 				current_scope[str] = this;
diff --git a/frontends/verilog/verilog_lexer.l b/frontends/verilog/verilog_lexer.l
index 19e54816d..6217b5728 100644
--- a/frontends/verilog/verilog_lexer.l
+++ b/frontends/verilog/verilog_lexer.l
@@ -265,6 +265,7 @@ static bool isUserType(std::string &s)
 "bit"        { SV_KEYWORD(TOK_LOGIC); }
 "int"        { SV_KEYWORD(TOK_INT); }
 "byte"       { SV_KEYWORD(TOK_BYTE); }
+"shortint"   { SV_KEYWORD(TOK_SHORTINT); }
 
 "eventually"   { if (formal_mode) return TOK_EVENTUALLY; SV_KEYWORD(TOK_EVENTUALLY); }
 "s_eventually" { if (formal_mode) return TOK_EVENTUALLY; SV_KEYWORD(TOK_EVENTUALLY); }
@@ -284,8 +285,9 @@ static bool isUserType(std::string &s)
 
 "enum"    { SV_KEYWORD(TOK_ENUM); }
 "typedef" { SV_KEYWORD(TOK_TYPEDEF); }
-"struct" { SV_KEYWORD(TOK_STRUCT); }
-"packed" { SV_KEYWORD(TOK_PACKED); }
+"struct"  { SV_KEYWORD(TOK_STRUCT); }
+"union"   { SV_KEYWORD(TOK_UNION); }
+"packed"  { SV_KEYWORD(TOK_PACKED); }
 
 [0-9][0-9_]* {
 	yylval->string = new std::string(yytext);
diff --git a/frontends/verilog/verilog_parser.y b/frontends/verilog/verilog_parser.y
index dbd18bb53..fff02f33a 100644
--- a/frontends/verilog/verilog_parser.y
+++ b/frontends/verilog/verilog_parser.y
@@ -238,6 +238,7 @@ static void rewriteAsMemoryNode(AstNode *node, AstNode *rangeNode)
 %union {
 	std::string *string;
 	struct YOSYS_NAMESPACE_PREFIX AST::AstNode *ast;
+	YOSYS_NAMESPACE_PREFIX AST::AstNodeType type;
 	YOSYS_NAMESPACE_PREFIX dict<YOSYS_NAMESPACE_PREFIX RTLIL::IdString, YOSYS_NAMESPACE_PREFIX AST::AstNode*> *al;
 	struct specify_target *specify_target_ptr;
 	struct specify_triple *specify_triple_ptr;
@@ -269,7 +270,7 @@ static void rewriteAsMemoryNode(AstNode *node, AstNode *rangeNode)
 %token TOK_POS_INDEXED TOK_NEG_INDEXED TOK_PROPERTY TOK_ENUM TOK_TYPEDEF
 %token TOK_RAND TOK_CONST TOK_CHECKER TOK_ENDCHECKER TOK_EVENTUALLY
 %token TOK_INCREMENT TOK_DECREMENT TOK_UNIQUE TOK_PRIORITY
-%token TOK_STRUCT TOK_PACKED TOK_UNSIGNED TOK_INT TOK_BYTE
+%token TOK_STRUCT TOK_PACKED TOK_UNSIGNED TOK_INT TOK_BYTE TOK_SHORTINT TOK_UNION 
 
 %type <ast> range range_or_multirange  non_opt_range non_opt_multirange range_or_signed_int
 %type <ast> wire_type expr basic_expr concat_list rvalue lvalue lvalue_concat_list
@@ -278,6 +279,7 @@ static void rewriteAsMemoryNode(AstNode *node, AstNode *rangeNode)
 %type <ast> opt_enum_init enum_type struct_type non_wire_data_type
 %type <boolean> opt_signed opt_property unique_case_attr always_comb_or_latch always_or_always_ff
 %type <al> attr case_attr
+%type <type> struct_union
 
 %type <specify_target_ptr> specify_target
 %type <specify_triple_ptr> specify_triple specify_opt_triple
@@ -328,7 +330,6 @@ design:
 	param_decl design |
 	localparam_decl design |
 	typedef_decl design |
-	struct_decl design |
 	package design |
 	interface design |
 	/* empty */;
@@ -568,8 +569,7 @@ package_body:
 	;
 
 package_body_stmt:
-	typedef_decl
-	| struct_decl
+	  typedef_decl
 	| localparam_decl
 	| param_decl
 	;
@@ -601,7 +601,7 @@ interface_body:
 	interface_body interface_body_stmt |;
 
 interface_body_stmt:
-	param_decl | localparam_decl | typedef_decl | struct_decl | defparam_decl | wire_decl | always_stmt | assign_stmt |
+	param_decl | localparam_decl | typedef_decl | defparam_decl | wire_decl | always_stmt | assign_stmt |
 	modport_stmt;
 
 non_opt_delay:
@@ -1442,6 +1442,7 @@ enum_base_type: type_atom type_signing
 
 type_atom: TOK_INTEGER		{ astbuf1->is_reg = true; addRange(astbuf1); }		// 4-state signed
 	|  TOK_INT		{ astbuf1->is_reg = true; addRange(astbuf1); }		// 2-state signed
+	|  TOK_SHORTINT		{ astbuf1->is_reg = true; addRange(astbuf1, 15, 0); }	// 2-state signed
 	|  TOK_BYTE		{ astbuf1->is_reg = true; addRange(astbuf1,  7, 0); }	// 2-state signed
 	;
 
@@ -1467,6 +1468,7 @@ enum_name_decl:
 		auto node = astbuf1->clone();
 		node->str = *$1;
 		delete $1;
+		SET_AST_NODE_LOC(node, @1, @1);
 		delete node->children[0];
 		node->children[0] = $2 ?: new AstNode(AST_NONE);
 		astbuf2->children.push_back(node);
@@ -1490,6 +1492,7 @@ enum_var: TOK_ID {
 		ast_stack.back()->children.push_back(node);
 		node->str = *$1;
 		delete $1;
+		SET_AST_NODE_LOC(node, @1, @1);
 		node->is_enum = true;
 	}
 	;
@@ -1497,23 +1500,29 @@ enum_var: TOK_ID {
 enum_decl: enum_type enum_var_list ';'		{ delete $1; }
 	;
 
-/////////
-// struct
-/////////
+//////////////////
+// struct or union
+//////////////////
 
 struct_decl: struct_type struct_var_list ';' 	{ delete astbuf2; }
 	;
 
-struct_type: TOK_STRUCT { astbuf2 = new AstNode(AST_STRUCT); } opt_packed '{' struct_member_list '}' 	{ $$ = astbuf2; }
+struct_type: struct_union { astbuf2 = new AstNode($1); } opt_packed '{' struct_member_list '}' 	{ $$ = astbuf2; }
 	;
 
+struct_union:
+	  TOK_STRUCT		{ $$ = AST_STRUCT; }
+	| TOK_UNION		{ $$ = AST_UNION; }
+	;
+
+
 opt_packed: TOK_PACKED opt_signed_struct
-	| { frontend_verilog_yyerror("Only STRUCT PACKED supported at this time"); }
+	| { frontend_verilog_yyerror("Only PACKED supported at this time"); }
 	;
 
 opt_signed_struct:
 	  TOK_SIGNED		{ astbuf2->is_signed = true; }
-	| TOK_UNSIGNED
+	| TOK_UNSIGNED		{ astbuf2->is_signed = false; }
 	| // default is unsigned
 	;
 
@@ -1532,11 +1541,13 @@ member_name_list:
 member_name: TOK_ID {
 			astbuf1->str = $1->substr(1);
 			delete $1;
-			astbuf2->children.push_back(astbuf1->clone());
+			auto member_node = astbuf1->clone();
+			SET_AST_NODE_LOC(member_node, @1, @1);
+			astbuf2->children.push_back(member_node);
 		}
 	;
 
-struct_member_type: { astbuf1 = new AstNode(AST_STRUCT_ITEM); } member_type_token_list { SET_RULE_LOC(@$, @2, @$); }
+struct_member_type: { astbuf1 = new AstNode(AST_STRUCT_ITEM); } member_type_token_list
 	;
 
 member_type_token_list:
@@ -1544,12 +1555,18 @@ member_type_token_list:
 	| hierarchical_type_id {
 			// use a clone of the typedef definition nodes
 			auto template_node = copyTypeDefinition(*$1);
-			if (template_node->type != AST_WIRE) {
+			delete $1;
+			switch (template_node->type) {
+			case AST_WIRE:
+				template_node->type = AST_STRUCT_ITEM;
+				break;
+			case AST_STRUCT:
+			case AST_UNION:
+				break;
+			default:
 				frontend_verilog_yyerror("Invalid type for struct member: %s", type2str(template_node->type).c_str());
 			}
-			template_node->type = AST_STRUCT_ITEM;
 			delete astbuf1;
-			delete $1;
 			astbuf1 = template_node;
 		}
 	;
@@ -1565,6 +1582,7 @@ struct_var_list: struct_var
 struct_var: TOK_ID	{	auto *var_node = astbuf2->clone();
 				var_node->str = *$1;
 				delete $1;
+				SET_AST_NODE_LOC(var_node, @1, @1);
 				ast_stack.back()->children.push_back(var_node);
 			}
 	;
diff --git a/tests/svtypes/union_simple.sv b/tests/svtypes/union_simple.sv
new file mode 100644
index 000000000..fc23fe6e8
--- /dev/null
+++ b/tests/svtypes/union_simple.sv
@@ -0,0 +1,61 @@
+module top;
+
+	typedef struct packed {
+		byte a,b,c,d;
+	} byte4_t;
+
+	typedef union packed {
+		int	x;
+		byte4_t	y;
+	} w_t;
+
+	w_t w;
+
+	assign w.x = 'h42;
+	always_comb begin
+		assert(w.y.d == 8'h42);
+	end
+
+	typedef logic[4:0] reg_addr_t;
+	typedef logic[6:0] opcode_t;
+
+	typedef struct packed {
+		bit [6:0]  func7;
+		reg_addr_t rs2;
+		reg_addr_t rs1;
+		bit [2:0]  func3;
+		reg_addr_t rd;
+		opcode_t   opcode;
+	} R_t;
+
+	typedef struct packed {
+		bit[11:0]  imm;
+		reg_addr_t rs1;
+		bit[2:0]   func3;
+		reg_addr_t rd;
+		opcode_t   opcode;
+	} I_t;
+
+	typedef struct packed {
+		bit[19:0]  imm;
+		reg_addr_t rd;
+		opcode_t   opcode;
+	} U_t;
+
+	typedef union packed {
+		R_t	r;
+		I_t	i;
+		U_t	u;
+	} instruction_t;
+
+	instruction_t ir1;
+	assign ir1 = 32'h0AA01EB7;          //	lui t4,0xAA01
+	always_comb begin
+		assert(ir1.u.opcode == 'h37);
+		assert(ir1.r.opcode == 'h37);
+		assert(ir1.u.rd == 'd29);
+		assert(ir1.r.rd == 'd29);
+		assert(ir1.u.imm == 'hAA01);
+	end
+
+endmodule