Support for swapped ranges in second array dimension

frontends/ast/simplify.cc

@@ -465,10 +465,17 @@ 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)
 {
+	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
-	// TODO: Check for swapped indexes - see make_struct_index_range
 	log_assert(rnode->type==AST_RANGE);
 	auto left  = rnode->children[0];
 	auto right = rnode->children[1];
@@ -504,7 +511,7 @@ AstNode *AST::make_struct_member_range(AstNode *node, AstNode *member_node)
 		auto mrnode = node->children[0];
 		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;
 	}

tests/svtypes/struct_array.sv

@@ -59,6 +59,27 @@ module top;
 
 	always_comb assert(s3==80'hFC00_4200_0012_3400_FFFC);
 
+	// Same as s3, but with little endian bit addressing
+	struct packed {
+		bit [0:7] [0:7] a;	// 8 element packed array of bytes
+		bit [0:15] b;		// filler for non-zero offset
+	} s3_b;
+
+	initial begin
+		s3_b = '0;
+
+		s3_b.a[5:6] = 16'h1234;
+		s3_b.a[2] = 8'h42;
+
+		s3_b.a[0] = '1;
+		s3_b.a[0][6:7] = '0;
+
+		s3_b.b = '1;
+		s3_b.b[14:15] = '0;
+	end
+
+	always_comb assert(s3_b==80'hFC00_4200_0012_3400_FFFC);
+
 	// Note that the tests below for unpacked arrays in structs rely on the
 	// fact that they are actually packed in Yosys.
 
@@ -104,6 +125,27 @@ module top;
 
 	always_comb assert(s5==80'hFC00_4200_0012_3400_FFFC);
 
+	// Same as s5, but with little endian bit addressing
+	struct packed {
+		bit [0:7] a [0:7];	// 8 element unpacked array of bytes
+		bit [0:15] b;		// filler for non-zero offset
+	} s5_b;
+
+	initial begin
+		s5_b = '0;
+
+		s5_b.a[5:6] = 16'h1234;
+		s5_b.a[2] = 8'h42;
+
+		s5_b.a[0] = '1;
+		s5_b.a[0][6:7] = '0;
+
+		s5_b.b = '1;
+		s5_b.b[14:15] = '0;
+	end
+
+	always_comb assert(s5_b==80'hFC00_4200_0012_3400_FFFC);
+
 	// Same as s5, but using C-type unpacked array syntax
 	struct packed {
 		bit [7:0] a [8];	// 8 element unpacked array of bytes