Merge pull request #2122 from PeterCrozier/struct_array2

Support 2D bit arrays in structures. Optimise array indexing.

1 files changed, 62 insertions, 28 deletions

diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index ed46e9e32..7f9795d29 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -380,31 +380,66 @@ static int size_packed_struct(AstNode *snode, int base_offset)
 
 static AstNode *node_int(int ival)
 {
-	// maybe mkconst_int should have default values for the common integer case
-	return AstNode::mkconst_int(ival, true, 32);
+	return AstNode::mkconst_int(ival, true);
 }
 
-static AstNode *offset_indexed_range(int offset_right, int stride, AstNode *left_expr, AstNode *right_expr)
+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)
 {
 	// 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) {
-		// just add the offset
-		left  = new AstNode(AST_ADD, node_int(offset_right), left);
-		right = new AstNode(AST_ADD, node_int(offset_right), right);
+	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);
+	}
+	return new AstNode(AST_RANGE, left, right);
+}
+
+static AstNode *make_struct_index_range(AstNode *node, AstNode *rnode, int stride, int offset)
+{
+	// generate a range node to perform either bit or array indexing
+	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]);
 	}
 	else {
-		// newleft = offset_right - 1 + (left + 1) * stride
-		left  = new AstNode(AST_ADD, new AstNode(AST_SUB, node_int(offset_right), node_int(1)),
-				new AstNode(AST_MUL, node_int(stride), new AstNode(AST_ADD, left, node_int(1))));
-		// newright = offset_right + right * stride
-		right = new AstNode(AST_ADD, node_int(offset_right), new AstNode(AST_MUL, right, node_int(stride)));
+		struct_op_error(node);
 	}
+}
+
+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);
 }
 
+
 static AstNode *make_struct_member_range(AstNode *node, AstNode *member_node)
 {
 	// Work out the range in the packed array that corresponds to a struct member
@@ -414,27 +449,26 @@ static AstNode *make_struct_member_range(AstNode *node, AstNode *member_node)
 	int range_right = member_node->range_right;
 	if (node->children.empty()) {
 		// no range operations apply, return the whole width
+		return make_range(range_left, range_right);
 	}
-	else if (node->children.size() == 1 && node->children[0]->type == AST_RANGE) {
-		auto rnode = node->children[0];
-		int stride = get_struct_array_width(member_node);
-		if (rnode->children.size() == 1) {
-			// index e.g. s.a[i]
-			return offset_indexed_range(range_right, stride, rnode->children[0], rnode->children[0]);
-		}
-		else if (rnode->children.size() == 2) {
-			// slice e.g. s.a[i:j]
-			return offset_indexed_range(range_right, stride, rnode->children[0], rnode->children[1]);
-		}
-		else {
-			struct_op_error(node);
-		}
+	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);
+	}
+	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;
 	}
 	else {
-		// TODO multirange, i.e. bit slice after array index s.a[i][p:q]
 		struct_op_error(node);
 	}
-	return make_range(range_left, range_right);
 }
 
 static void add_members_to_scope(AstNode *snode, std::string name)