init

    pub fn init(builder: *Builder, options: struct {
        function: Function.Index,
        strip: bool,
    }) Allocator.Error!WipFunction {
        var self: WipFunction = .{
            .builder = builder,
            .function = options.function,
            .prev_debug_location = .no_location,
            .debug_location = .no_location,
            .cursor = undefined,
            .blocks = .empty,
            .instructions = .empty,
            .names = .empty,
            .strip = options.strip,
            .debug_locations = .empty,
            .debug_values = .empty,
            .extra = .empty,
        };
        errdefer self.deinit();

        const params_len = options.function.typeOf(self.builder).functionParameters(self.builder).len;
        try self.ensureUnusedExtraCapacity(params_len, NoExtra, 0);
        try self.instructions.ensureUnusedCapacity(self.builder.gpa, params_len);
        if (!self.strip) {
            try self.names.ensureUnusedCapacity(self.builder.gpa, params_len);
        }
        for (0..params_len) |param_index| {
            self.instructions.appendAssumeCapacity(.{ .tag = .arg, .data = @intCast(param_index) });
            if (!self.strip) {
                self.names.appendAssumeCapacity(.empty); // TODO: param names
            }
        }

        return self;
    }