Commit 9377af934f5be92821f36b5d2255f086e5a84cda | zig

author	Andrew Kelley <andrew@ziglang.org> 2020-05-21 22:28:30-04:00
committer	Andrew Kelley <andrew@ziglang.org> 2020-05-21 22:28:30-04:00
log	9377af934f5be92821f36b5d2255f086e5a84cda
tree	e58814eecf85d3e59da6b7bc04c6a432fd1689cd
parent	d37b81d43bc52daa94dd1ad1631018ea0cd11f77

stage2 parser: SwitchCase uses intrusive array instead of linkedlist

no perf impact, but the API is better

3 files changed, 49 insertions(+), 29 deletions(-)

lib
- std
  - zig
    ast.zig
    parse.zig
    render.zig

lib/std/zig/ast.zig+30-9

 @@ -1552,28 +1552,35 @@ pub const Node = struct {
         }
     };
+    /// Items sub-nodes appear in memory directly following SwitchCase.
     pub const SwitchCase = struct {
         base: Node = Node{ .id = .SwitchCase },
-        items: ItemList,
         arrow_token: TokenIndex,
         payload: ?*Node,
         expr: *Node,
+        items_len: NodeIndex,
-        pub const ItemList = LinkedList(*Node);
+        /// After this the caller must initialize the fields_and_decls list.
+        pub fn alloc(allocator: *mem.Allocator, items_len: NodeIndex) !*SwitchCase {
+            const bytes = try allocator.alignedAlloc(u8, @alignOf(SwitchCase), sizeInBytes(items_len));
+            return @ptrCast(*SwitchCase, bytes.ptr);
+        }
+        pub fn free(self: *SwitchCase, allocator: *mem.Allocator) void {
+            const bytes = @ptrCast([*]u8, self)[0..sizeInBytes(self.items_len)];
+            allocator.free(bytes);
+        }
         pub fn iterate(self: *const SwitchCase) Node.Iterator {
-            return .{ .parent_node = &self.base, .index = 0, .node = self.items.first };
+            return .{ .parent_node = &self.base, .index = 0, .node = null };
         }
         pub fn iterateNext(self: *const SwitchCase, it: *Node.Iterator) ?*Node {
             var i = it.index;
             it.index += 1;
-            if (it.node) |child| {
+            if (i < self.items_len) return self.itemsConst()[i];
-                it.index -= 1;
+            i -= self.items_len;
-                it.node = child.next;
-                return child.data;
-            }
             if (self.payload) |payload| {
                 if (i < 1) return payload;
 @@ -1587,12 +1594,26 @@ pub const Node = struct {
         }
         pub fn firstToken(self: *const SwitchCase) TokenIndex {
-            return self.items.first.?.data.firstToken();
+            return self.itemsConst()[0].firstToken();
         }
         pub fn lastToken(self: *const SwitchCase) TokenIndex {
             return self.expr.lastToken();
         }
+        pub fn items(self: *SwitchCase) []*Node {
+            const decls_start = @ptrCast([*]u8, self) + @sizeOf(SwitchCase);
+            return @ptrCast([*]*Node, decls_start)[0..self.items_len];
+        }
+        pub fn itemsConst(self: *const SwitchCase) []const *Node {
+            const decls_start = @ptrCast([*]const u8, self) + @sizeOf(SwitchCase);
+            return @ptrCast([*]const *Node, decls_start)[0..self.items_len];
+        }
+        fn sizeInBytes(items_len: NodeIndex) usize {
+            return @sizeOf(SwitchCase) + @sizeOf(*Node) * @as(usize, items_len);
+        }
     };
     pub const SwitchElse = struct {

lib/std/zig/parse.zig+8-7

 @@ -2205,30 +2205,31 @@ const Parser = struct {
     ///     <- SwitchItem (COMMA SwitchItem)* COMMA?
     ///      / KEYWORD_else
     fn parseSwitchCase(p: *Parser) !?*Node {
-        var list = Node.SwitchCase.ItemList{};
+        var list = std.ArrayList(*Node).init(p.gpa);
-        var list_it = &list.first;
+        defer list.deinit();
         if (try p.parseSwitchItem()) |first_item| {
-            list_it = try p.llpush(*Node, list_it, first_item);
+            try list.append(first_item);
             while (p.eatToken(.Comma) != null) {
                 const next_item = (try p.parseSwitchItem()) orelse break;
-                list_it = try p.llpush(*Node, list_it, next_item);
+                try list.append(next_item);
             }
         } else if (p.eatToken(.Keyword_else)) |else_token| {
             const else_node = try p.arena.allocator.create(Node.SwitchElse);
             else_node.* = .{
                 .token = else_token,
             };
-            list_it = try p.llpush(*Node, list_it, &else_node.base);
+            try list.append(&else_node.base);
         } else return null;
-        const node = try p.arena.allocator.create(Node.SwitchCase);
+        const node = try Node.SwitchCase.alloc(&p.arena.allocator, list.items.len);
         node.* = .{
-            .items = list,
+            .items_len = list.items.len,
             .arrow_token = undefined, // set by caller
             .payload = null,
             .expr = undefined, // set by caller
         };
+        std.mem.copy(*Node, node.items(), list.items);
         return &node.base;
     }

lib/std/zig/render.zig+11-13

 @@ -1613,37 +1613,35 @@ fn renderExpression(
         .SwitchCase => {
             const switch_case = @fieldParentPtr(ast.Node.SwitchCase, "base", base);
-            assert(switch_case.items.first != null);
+            assert(switch_case.items_len != 0);
             const src_has_trailing_comma = blk: {
-                const last_node = switch_case.items.first.?.findLast().data;
+                const last_node = switch_case.items()[switch_case.items_len - 1];
                 const maybe_comma = tree.nextToken(last_node.lastToken());
                 break :blk tree.tokens[maybe_comma].id == .Comma;
             };
-            if (switch_case.items.first.?.next == null or !src_has_trailing_comma) {
+            if (switch_case.items_len == 1 or !src_has_trailing_comma) {
-                var it = switch_case.items.first;
+                const items = switch_case.items();
-                while (it) |node_node| : (it = node_node.next) {
+                for (items) |node, i| {
-                    const node = node_node.data;
+                    if (i + 1 < items.len) {
-                    if (node_node.next) |next_node| {
                         try renderExpression(allocator, stream, tree, indent, start_col, node, Space.None);
                         const comma_token = tree.nextToken(node.lastToken());
                         try renderToken(tree, stream, comma_token, indent, start_col, Space.Space); // ,
-                        try renderExtraNewline(tree, stream, start_col, next_node.data);
+                        try renderExtraNewline(tree, stream, start_col, items[i + 1]);
                     } else {
                         try renderExpression(allocator, stream, tree, indent, start_col, node, Space.Space);
                     }
                 }
             } else {
-                var it = switch_case.items.first;
+                const items = switch_case.items();
-                while (it) |node_node| : (it = node_node.next) {
+                for (items) |node, i| {
-                    const node = node_node.data;
+                    if (i + 1 < items.len) {
-                    if (node_node.next) |next_node| {
                         try renderExpression(allocator, stream, tree, indent, start_col, node, Space.None);
                         const comma_token = tree.nextToken(node.lastToken());
                         try renderToken(tree, stream, comma_token, indent, start_col, Space.Newline); // ,
-                        try renderExtraNewline(tree, stream, start_col, next_node.data);
+                        try renderExtraNewline(tree, stream, start_col, items[i + 1]);
                         try stream.writeByteNTimes(' ', indent);
                     } else {
                         try renderExpression(allocator, stream, tree, indent, start_col, node, Space.Comma);