(defun builds (flag)
  (declare (optimize (speed 3) (safety 0) (space 3) (debug 0)))
  (lambda ()
    (declare (optimize (speed 3) (safety 0) (space 3) (debug 0)))
    (when flag
      (print "smth"))
    (+ 1 2)))

(disassemble (builds nil))

; disassembly for (Λ () :IN BUILDS)
; Size: 59 bytes. Origin: #x53EA0F7A                          ; (Λ ()
                                                                  :IN
                                                                  BUILDS)
; 7A:       483D17011050     CMP RAX, #x50100117              ; NIL
; 80:       741C             JEQ L0
; 82:       4883EC10         SUB RSP, 16
; 86:       488B154BFFFFFF   MOV RDX, [RIP-181]               ; "smth"
; 8D:       B902000000       MOV ECX, 2
; 92:       48892C24         MOV [RSP], RBP
; 96:       488BEC           MOV RBP, RSP
; 99:       E8841E4FFC       CALL #x50392E22                  ; #<FDEFN PRINT>
; 9E: L0:   BA06000000       MOV EDX, 6
; A3:       488BE5           MOV RSP, RBP
; A6:       F8               CLC
; A7:       5D               POP RBP
; A8:       C3               RET
; A9:       6A21             PUSH 33
; AB:       E8D5F5B5FE       CALL #x52A00585                  ; CONS->R11
; B0:       E96BFFFFFF       JMP #x53EA0F20