test.asm

; compiled via:
; C:\temp>cl /O2 /nologo /c /FAs test.cpp

; Listing generated by Microsoft (R) Optimizing Compiler Version 16.00.40219.01

        TITLE   C:\temp\test.cpp
        .686P
        .XMM
        include listing.inc
        .model  flat

INCLUDELIB LIBCMT
INCLUDELIB OLDNAMES

PUBLIC  ?f@@YA_KH@Z                                     ; f
EXTRN   __allshl:PROC
; Function compile flags: /Ogtpy
; File c:\temp\test.cpp
;       COMDAT ?f@@YA_KH@Z
_TEXT   SEGMENT
_n$ = 8                                                 ; size = 4
?f@@YA_KH@Z PROC                                        ; f, COMDAT

; 3    :   return 1ull << n;

        mov     ecx, DWORD PTR _n$[esp-4]
        mov     eax, 1
        xor     edx, edx
        jmp     __allshl
?f@@YA_KH@Z ENDP                                        ; f
_TEXT   ENDS
END

test.cpp

unsigned long long f(int n)
{
  return 1ull << n;
}