1 files changed, 93 insertions, 71 deletions

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index c932e2c49..da7933d2f 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -285,10 +285,9 @@ static void save_struct_array_width(AstNode *node, int width)
 
 }
 
-static int get_struct_array_width(AstNode *node)
+static void save_struct_range_swapped(AstNode *node, bool range_swapped)
 {
-	// the stride for the array, 1 if not an array
-	return (node->multirange_dimensions.empty() ? 1 : node->multirange_dimensions.back());
+	node->multirange_swapped.push_back(range_swapped);
 
 }
 
@@ -318,38 +317,49 @@ 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
+						// The Yosys extension for unpacked arrays in packed structs / unions
+						// only supports memories, i.e. e.g. logic [7:0] a [256] - see above.
 						struct_array_packing_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) {
-				// 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
+			else if (node->children.size() > 0 && node->children[0]->type == AST_MULTIRANGE) {
+				// Packed array, e.g. bit [3:0][63:0] a
+				if (node->children.size() != 1) {
+					// The Yosys extension for unpacked arrays in packed structs / unions
+					// only supports memories, i.e. e.g. logic [7:0] a [256] - see above.
 					struct_array_packing_error(node);
 				}
-				int array_count = range_width(node, rnode->children[0]);
-				width = range_width(node, rnode->children[1]);
-				save_struct_array_width(node, width);
-				width *= array_count;
+				width = 1;
+				for (auto rnode : node->children[0]->children) {
+					int rwidth = range_width(node, rnode);
+					save_struct_array_width(node, rwidth);
+					save_struct_range_swapped(node, rnode->range_swapped);
+					width *= rwidth;
+				}
 				// range nodes are now redundant
 				for (AstNode *child : node->children)
 					delete child;
@@ -408,55 +418,51 @@ static AstNode *multiply_by_const(AstNode *expr_node, int stride)
 	return new AstNode(AST_MUL, expr_node, node_int(stride));
 }
 
-static AstNode *offset_indexed_range(int offset, int stride, AstNode *left_expr, AstNode *right_expr)
+static AstNode *normalize_struct_index(AstNode *expr, AstNode *member_node, int dimension)
 {
-	// adjust the range expressions to add an offset into the struct
-	// and maybe index using an array stride
-	auto left  = left_expr->clone();
-	auto right = right_expr->clone();
-	if (stride > 1) {
-		// newleft = (left + 1) * stride - 1
-		left  = new AstNode(AST_SUB, multiply_by_const(new AstNode(AST_ADD, left, node_int(1)), stride), node_int(1));
-		// newright = right * stride
-		right = multiply_by_const(right, stride);
-	}
-	// add the offset
-	if (offset) {
-		left  = new AstNode(AST_ADD, node_int(offset), left);
-		right = new AstNode(AST_ADD, node_int(offset), right);
+	expr = expr->clone();
+
+	if (member_node->multirange_swapped[dimension]) {
+		// The dimension has swapped range; swap index into the struct accordingly.
+		int msb = member_node->multirange_dimensions[dimension] - 1;
+		expr = new AstNode(AST_SUB, node_int(msb), expr);
 	}
-	return new AstNode(AST_RANGE, left, right);
+
+	return expr;
 }
 
-static AstNode *make_struct_index_range(AstNode *node, AstNode *rnode, int stride, int offset)
+static AstNode *struct_index_lsb_offset(AstNode *lsb_offset, AstNode *rnode, AstNode *member_node, int dimension, int &stride)
 {
-	// generate a range node to perform either bit or array indexing
+	stride /= member_node->multirange_dimensions[dimension];
+	auto right = normalize_struct_index(rnode->children.back(), member_node, dimension);
+	auto offset = stride > 1 ? multiply_by_const(right, stride) : right;
+	return new AstNode(AST_ADD, lsb_offset, offset);
+}
+
+static AstNode *struct_index_msb_offset(AstNode *lsb_offset, AstNode *rnode, AstNode *member_node, int dimension, int stride)
+{
+	log_assert(rnode->children.size() <= 2);
+
+	// Offset to add to LSB
+	AstNode *offset;
 	if (rnode->children.size() == 1) {
-		// index e.g. s.a[i]
-		return offset_indexed_range(offset, stride, rnode->children[0], rnode->children[0]);
-	}
-	else if (rnode->children.size() == 2) {
-		// slice e.g. s.a[i:j]
-		return offset_indexed_range(offset, stride, rnode->children[0], rnode->children[1]);
+		// Index, e.g. s.a[i]
+		offset = node_int(stride - 1);
 	}
 	else {
-		struct_op_error(node);
+		// rnode->children.size() == 2
+		// Slice, e.g. s.a[i:j]
+		auto left = normalize_struct_index(rnode->children[0], member_node, dimension);
+		auto right = normalize_struct_index(rnode->children[1], member_node, dimension);
+		offset = new AstNode(AST_SUB, left, right);
+		if (stride > 1) {
+			// offset = (msb - lsb + 1)*stride - 1
+			auto slice_width = new AstNode(AST_ADD, offset, node_int(1));
+			offset = new AstNode(AST_SUB, multiply_by_const(slice_width, stride), node_int(1));
+		}
 	}
-}
 
-static AstNode *slice_range(AstNode *rnode, AstNode *snode)
-{
-	// apply the bit slice indicated by snode to the range rnode
-	log_assert(rnode->type==AST_RANGE);
-	auto left  = rnode->children[0];
-	auto right = rnode->children[1];
-	log_assert(snode->type==AST_RANGE);
-	auto slice_left  = snode->children[0];
-	auto slice_right = snode->children[1];
-	auto width = new AstNode(AST_SUB, slice_left->clone(), slice_right->clone());
-	right = new AstNode(AST_ADD, right->clone(), slice_right->clone());
-	left  = new AstNode(AST_ADD, right->clone(), width);
-	return new AstNode(AST_RANGE, left, right);
+	return new AstNode(AST_ADD, lsb_offset, offset);
 }
 
 
@@ -471,24 +477,38 @@ 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);
 	}
-	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);
+
+	if (node->children.size() != 1) {
+		struct_op_error(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);
-		// then apply bit slice range
-		auto range = slice_range(element_range, mrnode->children[1]);
-		delete element_range;
-		return range;
+
+	// Range operations
+	auto rnode = node->children[0];
+	auto lsb_offset = node_int(member_node->range_right);
+	int stride = range_left - range_right + 1;
+	size_t i = 0;
+
+	// Calculate LSB offset for the final index / slice
+	if (rnode->type == AST_RANGE) {
+		lsb_offset = struct_index_lsb_offset(lsb_offset, rnode, member_node, i, stride);
+	}
+	else if (rnode->type == AST_MULTIRANGE) {
+		// Add offset for each dimension
+		auto mrnode = rnode;
+		for (i = 0; i < mrnode->children.size(); i++) {
+			rnode = mrnode->children[i];
+			lsb_offset = struct_index_lsb_offset(lsb_offset, rnode, member_node, i, stride);
+		}
+		i--;  // Step back to the final index / slice
 	}
 	else {
 		struct_op_error(node);
 	}
+
+	// Calculate MSB offset for the final index / slice
+	auto msb_offset = struct_index_msb_offset(lsb_offset->clone(), rnode, member_node, i, stride);
+
+	return new AstNode(AST_RANGE, msb_offset, lsb_offset);
 }
 
 static void add_members_to_scope(AstNode *snode, std::string name)
@@ -1587,6 +1607,8 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			break;
 		if (type == AST_GENBLOCK)
 			break;
+		if (type == AST_CELLARRAY && children[i]->type == AST_CELL)
+			continue;
 		if (type == AST_BLOCK && !str.empty())
 			break;
 		if (type == AST_PREFIX && i >= 1)