From d06258f74f724ea3ed26ec9341dd64a51e320ccf Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sat, 1 Feb 2014 13:50:23 +0100
Subject: [PATCH] Added constant size expression support of sized constants

---
 README                     |  4 ++++
 frontends/ast/ast.cc       |  1 +
 frontends/ast/ast.h        |  1 +
 frontends/ast/genrtlil.cc  |  8 ++++++++
 frontends/ast/simplify.cc  | 12 ++++++++++++
 frontends/verilog/parser.y | 22 ++++++++++++++++++++++
 6 files changed, 48 insertions(+)

diff --git a/README b/README
index f0c9bc747..ee5eb7979 100644
--- a/README
+++ b/README
@@ -275,6 +275,10 @@ Verilog Attributes and non-standard features
   always block: "assert(<expression>);". It is transformed to a $assert cell
   that is supported by the "sat" and "write_btor" commands.
 
+- Sized constants (the syntax <size>'s?[bodh]<value>) support constant
+  expressions as <size>. If the expresion is not a simple identifier, it
+  must be put in parentheses. Examples: WIDTH'd42, (4+2)'b101010
+
 
 Workarounds for known build problems
 ====================================
diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 40f7826f1..96608ae37 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -82,6 +82,7 @@ std::string AST::type2str(AstNodeType type)
 	X(AST_PREFIX)
 	X(AST_ASSERT)
 	X(AST_FCALL)
+	X(AST_TO_BITS)
 	X(AST_TO_SIGNED)
 	X(AST_TO_UNSIGNED)
 	X(AST_CONCAT)
diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index caae679a1..01702c3cf 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -61,6 +61,7 @@ namespace AST
 		AST_ASSERT,
 
 		AST_FCALL,
+		AST_TO_BITS,
 		AST_TO_SIGNED,
 		AST_TO_UNSIGNED,
 		AST_CONCAT,
diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index 6001e278a..99d8566dc 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -664,6 +664,14 @@ void AstNode::detectSignWidthWorker(int &width_hint, bool &sign_hint)
 			sign_hint = false;
 		break;
 
+	case AST_TO_BITS:
+		while (children[0]->simplify(true, false, false, 1, -1, false) == true) { }
+		if (children[0]->type != AST_CONSTANT)
+			log_error("Left operand of tobits expression is not constant at %s:%d!\n", filename.c_str(), linenum);
+		children[1]->detectSignWidthWorker(sub_width_hint, sign_hint);
+		width_hint = std::max(width_hint, children[0]->bitsAsConst().as_int());
+		break;
+
 	case AST_TO_SIGNED:
 		children.at(0)->detectSignWidthWorker(width_hint, sub_sign_hint);
 		break;
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 5a2d1ae6c..f19befe2a 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -258,6 +258,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		}
 		break;
 
+	case AST_TO_BITS:
 	case AST_TO_SIGNED:
 	case AST_TO_UNSIGNED:
 	case AST_CONCAT:
@@ -442,6 +443,17 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		goto apply_newNode;
 	}
 
+	// evaluate TO_BITS nodes
+	if (type == AST_TO_BITS) {
+		if (children[0]->type != AST_CONSTANT)
+			log_error("Left operand of to_bits expression is not constant at %s:%d!\n", filename.c_str(), linenum);
+		if (children[1]->type != AST_CONSTANT)
+			log_error("Right operand of to_bits expression is not constant at %s:%d!\n", filename.c_str(), linenum);
+		RTLIL::Const new_value = children[1]->bitsAsConst(children[0]->bitsAsConst().as_int(), children[1]->is_signed);
+		newNode = mkconst_bits(new_value.bits, children[1]->is_signed);
+		goto apply_newNode;
+	}
+
 	// annotate constant ranges
 	if (type == AST_RANGE) {
 		bool old_range_valid = range_valid;
diff --git a/frontends/verilog/parser.y b/frontends/verilog/parser.y
index b0c4db8ae..5b6bf58c2 100644
--- a/frontends/verilog/parser.y
+++ b/frontends/verilog/parser.y
@@ -1051,6 +1051,28 @@ basic_expr:
 	rvalue {
 		$$ = $1;
 	} |
+	'(' expr ')' TOK_CONST {
+		if ($4->substr(0, 1) != "'")
+			frontend_verilog_yyerror("Syntax error.");
+		AstNode *bits = $2;
+		AstNode *val = const2ast(*$4, case_type_stack.size() == 0 ? 0 : case_type_stack.back());
+		if (val == NULL)
+			log_error("Value conversion failed: `%s'\n", $4->c_str());
+		$$ = new AstNode(AST_TO_BITS, bits, val);
+		delete $4;
+	} |
+	hierarchical_id TOK_CONST {
+		if ($2->substr(0, 1) != "'")
+			frontend_verilog_yyerror("Syntax error.");
+		AstNode *bits = new AstNode(AST_IDENTIFIER);
+		bits->str = *$1;
+		AstNode *val = const2ast(*$2, case_type_stack.size() == 0 ? 0 : case_type_stack.back());
+		if (val == NULL)
+			log_error("Value conversion failed: `%s'\n", $2->c_str());
+		$$ = new AstNode(AST_TO_BITS, bits, val);
+		delete $1;
+		delete $2;
+	} |
 	TOK_CONST {
 		$$ = const2ast(*$1, case_type_stack.size() == 0 ? 0 : case_type_stack.back());
 		if ($$ == NULL)
-- 
2.30.2