format

            fn format(data: FormatData, w: *Writer) Writer.Error!void {
                if (data.flags.comma) {
                    if (data.instruction == .none) return;
                    try w.writeByte(',');
                }
                if (data.flags.space) {
                    if (data.instruction == .none) return;
                    try w.writeByte(' ');
                }
                if (data.flags.percent) try w.print(
                    "{f} ",
                    .{data.instruction.typeOf(data.function, data.builder).fmt(data.builder, .percent)},
                );
                assert(data.instruction != .none);
                try w.print("%{f}", .{
                    data.instruction.name(data.function.ptrConst(data.builder)).fmt(data.builder),
                });
            }