Merge pull request #3551 from daglem/struct-array-swapped-range

Support for arrays with swapped ranges within structs

2 files changed, 61 insertions, 21 deletions

diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 80497c131..142ec0801 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -203,7 +203,7 @@ namespace AST
 
 		// if this is a multirange memory then this vector contains offset and length of each dimension
 		std::vector<int> multirange_dimensions;
-		std::vector<bool> multirange_swapped; // true if range is swapped, not used for structs
+		std::vector<bool> multirange_swapped; // true if range is swapped
 
 		// this is set by simplify and used during RTLIL generation
 		AstNode *id2ast;
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index c932e2c49..57237f4b3 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -273,9 +273,9 @@ static int range_width(AstNode *node, AstNode *rnode)
 	return rnode->range_left - rnode->range_right + 1;
 }
 
-[[noreturn]] static void struct_array_packing_error(AstNode *node)
+[[noreturn]] static void struct_array_dimension_error(AstNode *node)
 {
-	log_file_error(node->filename, node->location.first_line, "Unpacked array in packed struct/union member %s\n", node->str.c_str());
+	log_file_error(node->filename, node->location.first_line, "Currently limited to two dimensions in packed struct/union member %s\n", node->str.c_str());
 }
 
 static void save_struct_array_width(AstNode *node, int width)
@@ -285,10 +285,18 @@ static void save_struct_array_width(AstNode *node, int width)
 
 }
 
+static void save_struct_range_swapped(AstNode *node, bool range_swapped)
+{
+	node->multirange_swapped.push_back(range_swapped);
+
+}
+
 static int get_struct_array_width(AstNode *node)
 {
+	// This function is only useful for up to two array dimensions.
+	log_assert(node->multirange_dimensions.size() <= 2);
 	// the stride for the array, 1 if not an array
-	return (node->multirange_dimensions.empty() ? 1 : node->multirange_dimensions.back());
+	return (node->multirange_dimensions.size() != 2 ? 1 : node->multirange_dimensions[1]);
 
 }
 
@@ -318,37 +326,47 @@ static int size_packed_struct(AstNode *snode, int base_offset)
 				// member width e.g. bit [7:0] a
 				width = range_width(node, node->children[0]);
 				if (node->children.size() == 2) {
+					// Unpacked array. Note that this is a Yosys extension; only packed data types
+					// and integer data types are allowed in packed structs / unions in SystemVerilog.
 					if (node->children[1]->type == AST_RANGE) {
-						// unpacked array e.g. bit [63:0] a [0:3]
+						// Unpacked array, e.g. bit [63:0] a [0:3]
 						auto rnode = node->children[1];
-						int array_count = range_width(node, rnode);
-						if (array_count == 1) {
-							// C-type array size e.g. bit [63:0] a [4]
-							array_count = rnode->range_left;
-						}
+						// C-style array size, e.g. bit [63:0] a [4]
+						bool c_type = rnode->children.size() == 1;
+						int array_count = c_type ? rnode->range_left : range_width(node, rnode);
+						save_struct_array_width(node, array_count);
+						save_struct_range_swapped(node, rnode->range_swapped || c_type);
 						save_struct_array_width(node, width);
+						save_struct_range_swapped(node, node->children[0]->range_swapped);
 						width *= array_count;
 					}
 					else {
-						// array element must be single bit for a packed array
-						struct_array_packing_error(node);
+						// Currently limited to at most two dimensions.
+						struct_array_dimension_error(node);
 					}
+				} else {
+					// Vector.
+					save_struct_array_width(node, width);
+					save_struct_range_swapped(node, node->children[0]->range_swapped);
 				}
 				// range nodes are now redundant
 				for (AstNode *child : node->children)
 					delete child;
 				node->children.clear();
 			}
-			else if (node->children.size() == 1 && node->children[0]->type == AST_MULTIRANGE) {
+			else if (node->children.size() > 0 && node->children[0]->type == AST_MULTIRANGE) {
 				// packed 2D array, e.g. bit [3:0][63:0] a
 				auto rnode = node->children[0];
-				if (rnode->children.size() != 2) {
-					// packed arrays can only be 2D
-					struct_array_packing_error(node);
+				if (node->children.size() != 1 || rnode->children.size() != 2) {
+					// Currently limited to at most two dimensions.
+					struct_array_dimension_error(node);
 				}
 				int array_count = range_width(node, rnode->children[0]);
+				save_struct_array_width(node, array_count);
+				save_struct_range_swapped(node, rnode->children[0]->range_swapped);
 				width = range_width(node, rnode->children[1]);
 				save_struct_array_width(node, width);
+				save_struct_range_swapped(node, rnode->children[1]->range_swapped);
 				width *= array_count;
 				// range nodes are now redundant
 				for (AstNode *child : node->children)
@@ -428,8 +446,18 @@ static AstNode *offset_indexed_range(int offset, int stride, AstNode *left_expr,
 	return new AstNode(AST_RANGE, left, right);
 }
 
-static AstNode *make_struct_index_range(AstNode *node, AstNode *rnode, int stride, int offset)
+static AstNode *make_struct_index_range(AstNode *node, AstNode *rnode, int stride, int offset, AstNode *member_node)
 {
+	// This function should be rewritten to support more than two array dimensions.
+	log_assert(member_node->multirange_dimensions.size() <= 2 && member_node->multirange_swapped.size() <= 2);
+	if (member_node->multirange_swapped[0]) {
+		// The struct item has swapped range; swap index into the struct accordingly.
+		int msb = member_node->multirange_dimensions[0] - 1;
+		for (auto &expr : rnode->children) {
+			expr = new AstNode(AST_SUB, node_int(msb), expr);
+		}
+	}
+
 	// generate a range node to perform either bit or array indexing
 	if (rnode->children.size() == 1) {
 		// index e.g. s.a[i]
@@ -444,8 +472,18 @@ static AstNode *make_struct_index_range(AstNode *node, AstNode *rnode, int strid
 	}
 }
 
-static AstNode *slice_range(AstNode *rnode, AstNode *snode)
+static AstNode *slice_range(AstNode *rnode, AstNode *snode, AstNode *member_node)
 {
+	// This function should be rewritten to support more than two array dimensions.
+	log_assert(member_node->multirange_dimensions.size() <= 2 && member_node->multirange_swapped.size() <= 2);
+	if (member_node->multirange_swapped[1]) {
+		// The second dimension has swapped range; swap index into the struct accordingly.
+		int msb = member_node->multirange_dimensions[1] - 1;
+		for (auto &expr : snode->children) {
+			expr = new AstNode(AST_SUB, node_int(msb), expr);
+		}
+	}
+
 	// apply the bit slice indicated by snode to the range rnode
 	log_assert(rnode->type==AST_RANGE);
 	auto left  = rnode->children[0];
@@ -471,18 +509,20 @@ AstNode *AST::make_struct_member_range(AstNode *node, AstNode *member_node)
 		// no range operations apply, return the whole width
 		return make_range(range_left, range_right);
 	}
+	// This function should be rewritten to support more than two array dimensions.
+	log_assert(member_node->multirange_dimensions.size() <= 2 && member_node->multirange_swapped.size() <= 2);
 	int stride = get_struct_array_width(member_node);
 	if (node->children.size() == 1 && node->children[0]->type == AST_RANGE) {
 		// bit or array indexing e.g. s.a[2] or s.a[1:0]
-		return make_struct_index_range(node, node->children[0], stride, range_right);
+		return make_struct_index_range(node, node->children[0], stride, range_right, member_node);
 	}
 	else if (node->children.size() == 1 && node->children[0]->type == AST_MULTIRANGE) {
 		// multirange, i.e. bit slice after array index, e.g. s.a[i][p:q]
 		log_assert(stride > 1);
 		auto mrnode = node->children[0];
-		auto element_range = make_struct_index_range(node, mrnode->children[0], stride, range_right);
+		auto element_range = make_struct_index_range(node, mrnode->children[0], stride, range_right, member_node);
 		// then apply bit slice range
-		auto range = slice_range(element_range, mrnode->children[1]);
+		auto range = slice_range(element_range, mrnode->children[1], member_node);
 		delete element_range;
 		return range;
 	}