partial rebase of PeterCrozier's enum work onto current master

I tried to keep only the enum-related changes, and minimize the diff. (The
original commit also had a lot of work done to get typedefs working, but yosys
has diverged quite a bit since the 2018-03-09 commit, with a new typedef
implementation.) I did not include the import related changes either.

Original commit:
"Initial implementation of enum, typedef, import.  Still a WIP."
https://github.com/PeterCrozier/yosys/commit/881833aa738e7404987646ea8076284e911fce3f

4 files changed, 117 insertions, 16 deletions

diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 5bbea0faf..135750837 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -88,6 +88,8 @@ std::string AST::type2str(AstNodeType type)
 	X(AST_LIVE)
 	X(AST_FAIR)
 	X(AST_COVER)
+	X(AST_ENUM)
+	X(AST_ENUM_ITEM)
 	X(AST_FCALL)
 	X(AST_TO_BITS)
 	X(AST_TO_SIGNED)
@@ -202,6 +204,7 @@ AstNode::AstNode(AstNodeType type, AstNode *child1, AstNode *child2, AstNode *ch
 	is_logic = false;
 	is_signed = false;
 	is_string = false;
+	is_enum = false;
 	is_wand = false;
 	is_wor = false;
 	is_unsized = false;
@@ -321,6 +324,9 @@ void AstNode::dumpAst(FILE *f, std::string indent) const
 			fprintf(f, " %d", v);
 		fprintf(f, " ]");
 	}
+	if (is_enum) {
+		fprintf(f, " type=enum");
+	}
 	fprintf(f, "\n");
 
 	for (auto &it : attributes) {
@@ -1174,7 +1180,15 @@ void AST::process(RTLIL::Design *design, AstNode *ast, bool dump_ast1, bool dump
 			for (auto n : design->verilog_packages){
 				for (auto o : n->children) {
 					AstNode *cloned_node = o->clone();
-					cloned_node->str = n->str + std::string("::") + cloned_node->str.substr(1);
+					log("cloned node %s\n", type2str(cloned_node->type).c_str());
+					if (cloned_node->type == AST_ENUM){
+						for (auto e : cloned_node->children){
+							log_assert(e->type == AST_ENUM_ITEM);
+							e->str = n->str + std::string("::") + e->str.substr(1);
+						}
+					} else {
+						cloned_node->str = n->str + std::string("::") + cloned_node->str.substr(1);
+					}
 					(*it)->children.push_back(cloned_node);
 				}
 			}
@@ -1203,10 +1217,13 @@ void AST::process(RTLIL::Design *design, AstNode *ast, bool dump_ast1, bool dump
 
 			design->add(process_module(*it, defer));
 		}
-		else if ((*it)->type == AST_PACKAGE)
+		else if ((*it)->type == AST_PACKAGE) {
 			design->verilog_packages.push_back((*it)->clone());
-		else
+		}
+		else {
+			// must be global definition
 			design->verilog_globals.push_back((*it)->clone());
+		}
 	}
 }
 
diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 918d178c7..ffdcd9271 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -68,6 +68,8 @@ namespace AST
 		AST_LIVE,
 		AST_FAIR,
 		AST_COVER,
+		AST_ENUM,
+		AST_ENUM_ITEM,
 
 		AST_FCALL,
 		AST_TO_BITS,
@@ -181,6 +183,8 @@ namespace AST
 		int port_id, range_left, range_right;
 		uint32_t integer;
 		double realvalue;
+		// set for IDs typed to an enumeration, not used
+		bool is_enum;
 
 		// if this is a multirange memory then this vector contains offset and length of each dimension
 		std::vector<int> multirange_dimensions;
@@ -285,6 +289,9 @@ namespace AST
 		int isConst() const; // return '1' for AST_CONSTANT and '2' for AST_REALVALUE
 		double asReal(bool is_signed);
 		RTLIL::Const realAsConst(int width);
+
+		// helpers for enum
+		void allocateDefaultEnumValues();
 	};
 
 	// process an AST tree (ast must point to an AST_DESIGN node) and generate RTLIL code
diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index 94f5c0a04..76705c75f 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -595,6 +595,9 @@ void AstNode::detectSignWidthWorker(int &width_hint, bool &sign_hint, bool *foun
 
 	switch (type)
 	{
+	case AST_NONE:
+		// unallocated enum, ignore
+		break;
 	case AST_CONSTANT:
 		width_hint = max(width_hint, int(bits.size()));
 		if (!is_signed)
@@ -612,7 +615,7 @@ void AstNode::detectSignWidthWorker(int &width_hint, bool &sign_hint, bool *foun
 			id_ast = current_scope.at(str);
 		if (!id_ast)
 			log_file_error(filename, linenum, "Failed to resolve identifier %s for width detection!\n", str.c_str());
-		if (id_ast->type == AST_PARAMETER || id_ast->type == AST_LOCALPARAM) {
+		if (id_ast->type == AST_PARAMETER || id_ast->type == AST_LOCALPARAM || id_ast->type == AST_ENUM_ITEM) {
 			if (id_ast->children.size() > 1 && id_ast->children[1]->range_valid) {
 				this_width = id_ast->children[1]->range_left - id_ast->children[1]->range_right + 1;
 			} else
@@ -861,6 +864,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 	case AST_GENIF:
 	case AST_GENCASE:
 	case AST_PACKAGE:
+	case AST_ENUM:
 	case AST_MODPORT:
 	case AST_MODPORTMEMBER:
 	case AST_TYPEDEF:
@@ -1022,7 +1026,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 				else
 					log_file_error(filename, linenum, "Identifier `%s' is implicitly declared and `default_nettype is set to none.\n", str.c_str());
 			}
-			else if (id2ast->type == AST_PARAMETER || id2ast->type == AST_LOCALPARAM) {
+			else if (id2ast->type == AST_PARAMETER || id2ast->type == AST_LOCALPARAM || id2ast->type == AST_ENUM_ITEM) {
 				if (id2ast->children[0]->type != AST_CONSTANT)
 					log_file_error(filename, linenum, "Parameter %s does not evaluate to constant value!\n", str.c_str());
 				chunk = RTLIL::Const(id2ast->children[0]->bits);
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index b94a8d710..9013ebe66 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -318,13 +318,13 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 	}
 
 	// activate const folding if this is anything that must be evaluated statically (ranges, parameters, attributes, etc.)
-	if (type == AST_WIRE || type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_RANGE || type == AST_PREFIX || type == AST_TYPEDEF)
+	if (type == AST_WIRE || type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_ENUM_ITEM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_RANGE || type == AST_PREFIX || type == AST_TYPEDEF)
 		const_fold = true;
-	if (type == AST_IDENTIFIER && current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM))
+	if (type == AST_IDENTIFIER && current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM || current_scope[str]->type == AST_ENUM_ITEM))
 		const_fold = true;
 
 	// in certain cases a function must be evaluated constant. this is what in_param controls.
-	if (type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_PREFIX)
+	if (type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_LOCALPARAM || type == AST_ENUM_ITEM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_PREFIX)
 		in_param = true;
 
 	std::map<std::string, AstNode*> backup_scope;
@@ -405,12 +405,23 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 				}
 				this_wire_scope[node->str] = node;
 			}
+			// these nodes appear at the top level in a module and can define names
 			if (node->type == AST_PARAMETER || node->type == AST_LOCALPARAM || node->type == AST_WIRE || node->type == AST_AUTOWIRE || node->type == AST_GENVAR ||
 					node->type == AST_MEMORY || node->type == AST_FUNCTION || node->type == AST_TASK || node->type == AST_DPI_FUNCTION || node->type == AST_CELL ||
 					node->type == AST_TYPEDEF) {
 				backup_scope[node->str] = current_scope[node->str];
 				current_scope[node->str] = node;
 			}
+			if (node->type == AST_ENUM) {
+				for (auto enode : node->children) {
+					log_assert(enode->type==AST_ENUM_ITEM);
+					if (current_scope.count(enode->str) == 0) {
+						current_scope[enode->str] = enode;
+					}
+					//	while (enode->simplify(true, false, false, 1, -1, false, true))
+					//		did_something = true;
+				}
+			}
 		}
 		for (size_t i = 0; i < children.size(); i++) {
 			AstNode *node = children[i];
@@ -492,8 +503,21 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		}
 		break;
 
+	case AST_ENUM:
+		// log("\nENUM %d child %d\n", basic_prep, children[0]->basic_prep);
+		if (!basic_prep) {
+			for (auto item_node : children) {
+				while (!item_node->basic_prep && item_node->simplify(false, false, false, stage, -1, false, true) == true)
+					did_something = true;
+			}
+			// allocate values (called more than once)
+			allocateDefaultEnumValues();
+		}
+		break;
+
 	case AST_PARAMETER:
 	case AST_LOCALPARAM:
+	case AST_ENUM_ITEM:
 		while (!children[0]->basic_prep && children[0]->simplify(false, false, false, stage, -1, false, true) == true)
 			did_something = true;
 		children[0]->detectSignWidth(width_hint, sign_hint);
@@ -826,7 +850,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			// Insert clones children from template at beginning
 			for (int i  = 0; i < GetSize(templ->children); i++)
 				children.insert(children.begin() + i, templ->children[i]->clone());
-			
+
 			if (type == AST_MEMORY && GetSize(children) == 1) {
 				// Single-bit memories must have [0:0] range
 				AstNode *rng = new AstNode(AST_RANGE);
@@ -873,7 +897,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			did_something = true;
 		}
 		log_assert(!is_custom_type);
-	}	
+	}
 
 	// resolve constant prefixes
 	if (type == AST_PREFIX) {
@@ -1005,7 +1029,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 	}
 
 	// trim/extend parameters
-	if (type == AST_PARAMETER || type == AST_LOCALPARAM) {
+	if (type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_ENUM_ITEM) {
 		if (children.size() > 1 && children[1]->type == AST_RANGE) {
 			if (!children[1]->range_valid)
 				log_file_error(filename, linenum, "Non-constant width range on parameter decl.\n");
@@ -1046,10 +1070,32 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 	if (type == AST_IDENTIFIER) {
 		if (current_scope.count(str) == 0) {
 			for (auto node : current_ast_mod->children) {
-				if ((node->type == AST_PARAMETER || node->type == AST_LOCALPARAM || node->type == AST_WIRE || node->type == AST_AUTOWIRE || node->type == AST_GENVAR ||
-						node->type == AST_MEMORY || node->type == AST_FUNCTION || node->type == AST_TASK || node->type == AST_DPI_FUNCTION) && str == node->str) {
+				//log("looking at mod scope child %s\n", type2str(node->type).c_str());
+				switch (node->type) {
+				case AST_PARAMETER:
+				case AST_LOCALPARAM:
+				case AST_WIRE:
+				case AST_AUTOWIRE:
+				case AST_GENVAR:
+				case AST_MEMORY:
+				case AST_FUNCTION:
+				case AST_TASK:
+				case AST_DPI_FUNCTION:
+					//log("found child %s, %s\n", type2str(node->type).c_str(), node->str.c_str());
+					log("add %s, type %s to scope\n", str.c_str(), type2str(node->type).c_str());
 					current_scope[node->str] = node;
 					break;
+				case AST_ENUM:
+					for (auto enum_node : node->children) {
+						log_assert(enum_node->type==AST_ENUM_ITEM);
+						if (str == enum_node->str) {
+							log("\nadding enum %s to scope\n", str.c_str());
+							current_scope[str] = enum_node;
+						}
+					}
+					break;
+				default:
+					break;
 				}
 			}
 		}
@@ -2482,7 +2528,7 @@ skip_dynamic_range_lvalue_expansion:;
 		}
 
 		for (auto child : decl->children)
-			if (child->type == AST_WIRE || child->type == AST_MEMORY || child->type == AST_PARAMETER || child->type == AST_LOCALPARAM)
+			if (child->type == AST_WIRE || child->type == AST_MEMORY || child->type == AST_PARAMETER || child->type == AST_LOCALPARAM || child->type == AST_ENUM_ITEM)
 			{
 				AstNode *wire = nullptr;
 
@@ -2588,7 +2634,7 @@ replace_fcall_later:;
 		switch (type)
 		{
 		case AST_IDENTIFIER:
-			if (current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM)) {
+			if (current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM || current_scope[str]->type == AST_ENUM_ITEM)) {
 				if (current_scope[str]->children[0]->type == AST_CONSTANT) {
 					if (children.size() != 0 && children[0]->type == AST_RANGE && children[0]->range_valid) {
 						std::vector<RTLIL::State> data;
@@ -3025,7 +3071,7 @@ void AstNode::expand_genblock(std::string index_var, std::string prefix, std::ma
 	for (size_t i = 0; i < children.size(); i++) {
 		AstNode *child = children[i];
 		if (child->type == AST_WIRE || child->type == AST_MEMORY || child->type == AST_PARAMETER || child->type == AST_LOCALPARAM ||
-				child->type == AST_FUNCTION || child->type == AST_TASK || child->type == AST_CELL || child->type == AST_TYPEDEF) {
+				child->type == AST_FUNCTION || child->type == AST_TASK || child->type == AST_CELL || child->type == AST_TYPEDEF || child->type == AST_ENUM_ITEM) {
 			if (backup_name_map.size() == 0)
 				backup_name_map = name_map;
 			std::string new_name = prefix[0] == '\\' ? prefix.substr(1) : prefix;
@@ -3782,4 +3828,31 @@ AstNode *AstNode::eval_const_function(AstNode *fcall)
 	return AstNode::mkconst_bits(variables.at(str).val.bits, variables.at(str).is_signed);
 }
 
+void AstNode::allocateDefaultEnumValues()
+{
+	log_assert(type==AST_ENUM);
+	int last_enum_int = -1;
+	for (auto node : children) {
+		log_assert(node->type==AST_ENUM_ITEM);
+		for (size_t i = 0; i < node->children.size(); i++) {
+			switch (node->children[i]->type) {
+			case AST_NONE:
+				// replace with auto-incremented constant
+				delete node->children[i];
+				node->children[i] = AstNode::mkconst_int(++last_enum_int, true);
+				break;
+			case AST_CONSTANT:
+				// explicit constant (or folded expression)
+				// TODO: can't extend 'x or 'z item
+				last_enum_int = node->children[i]->integer;
+				break;
+			default:
+				// ignore ranges
+				break;
+			}
+			// TODO: range check
+		}
+	}
+}
+
 YOSYS_NAMESPACE_END