Assembly Language for Beginners

1.30. 64 BITS

mov DWORD PTR [edi], ebp
xor eax, ecx
mov ecx, DWORD PTR _out3$[esp+32]
xor eax, DWORD PTR [ecx]
pop edi
pop esi
xor eax, ebx
pop ebp
mov DWORD PTR [ecx], eax
pop ebx
add esp, 20
ret 0
_s1 ENDP

5 variables were allocated in the local stack by the compiler.

Now let’s try the same thing in the 64-bit version of MSVC 2008:

Listing 1.393: Optimizing MSVC 2008

a1$ = 56
a2$ = 64
a3$ = 72
a4$ = 80
x36$1$ = 88
a5$ = 88
a6$ = 96
out1$ = 104
out2$ = 112
out3$ = 120
out4$ = 128
s1 PROC
$LN3:
mov QWORD PTR [rsp+24], rbx
mov QWORD PTR [rsp+32], rbp
mov QWORD PTR [rsp+16], rdx
mov QWORD PTR [rsp+8], rcx
push rsi
push rdi
push r12
push r13
push r14
push r15
mov r15, QWORD PTR a5$[rsp]
mov rcx, QWORD PTR a6$[rsp]
mov rbp, r8
mov r10, r9
mov rax, r15
mov rdx, rbp
not rax
xor rdx, r9
not r10
mov r11, rax
and rax, r9
mov rsi, r10
mov QWORD PTR x36$1$[rsp], rax
and r11, r8
and rsi, r8
and r10, r15
mov r13, rdx
mov rbx, r11
xor rbx, r9
mov r9, QWORD PTR a2$[rsp]
mov r12, rsi
or r12, r15
not r13
and r13, rcx
mov r14, r12
and r14, rcx
mov rax, r14
mov r8, r14