diff

>diff Loop.s Recu.s
3c3
<     .globl  __Z4fibLi               ## -- Begin function _Z4fibLi
---
>     .globl  __Z4fibRi               ## -- Begin function _Z4fibRi
5c5
< __Z4fibLi:                              ## @_Z4fibLi
---
> __Z4fibRi:                              ## @_Z4fibRi
15c15
<     jl  LBB0_3
---
>     jl  LBB1_3
21c21
< LBB0_2:                                 ## =>This Inner Loop Header: Depth=1
---
> LBB1_2:                                 ## =>This Inner Loop Header: Depth=1
28,29c28,29
<     jg  LBB0_2
< LBB0_3:
---
>     jg  LBB1_2
> LBB1_3:

fib.cpp

#include <iostream>

#ifdef LOOP
int fibL(int n)
{
    int a = 1;  // f(0) => 1
    int b = 1;  // f(1) => 1

    for(; n >= 2 ; --n) {
        int c = a + b;
        a = b;
        b = c;
    }
    return b;
}
#endif

#ifdef RECU
int fibR(int a, int b, int n)
{
    if (n < 2) {
        return b;
    }
    return fibR(b, a+b,  n - 1);
}

int fibR(int n)
{
    return fibR(1, 1, n);
}
#endif

#ifdef APP
int main()
{
    std::cout << fibR(1) << " " << fibL(1) << "\n";
    std::cout << fibR(5) << " " << fibL(5) << "\n";
    std::cout << fibR(8) << " " << fibL(8) << "\n";
    std::cout << fibR(13) << " " << fibL(13) << "\n";
}
#endif

Loop.s

// Note I removed the header
    .globl  __Z4fibLi               ## -- Begin function _Z4fibLi
    .p2align    4, 0x90
__Z4fibLi:                              ## @_Z4fibLi
    .cfi_startproc
## %bb.0:
    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset %rbp, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register %rbp
    movl    $1, %eax
    cmpl    $2, %edi
    jl  LBB0_3
## %bb.1:
    incl    %edi
    movl    $1, %eax
    movl    $1, %ecx
    .p2align    4, 0x90
LBB0_2:                                 ## =>This Inner Loop Header: Depth=1
    movl    %eax, %edx
    movl    %ecx, %eax
    addl    %edx, %eax
    decl    %edi
    movl    %edx, %ecx
    cmpl    $2, %edi
    jg  LBB0_2
LBB0_3:
    popq    %rbp
    retq
    .cfi_endproc
                                        ## -- End function
.subsections_via_symbols

Recu.s

// Note I removed the header
// and the definition of fibR(int,int,int) as it is inlined below.
//
    .globl  __Z4fibRi               ## -- Begin function _Z4fibRi
    .p2align    4, 0x90
__Z4fibRi:                              ## @_Z4fibRi
    .cfi_startproc
## %bb.0:
    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset %rbp, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register %rbp
    movl    $1, %eax
    cmpl    $2, %edi
    jl  LBB1_3
## %bb.1:
    incl    %edi
    movl    $1, %eax
    movl    $1, %ecx
    .p2align    4, 0x90
LBB1_2:                                 ## =>This Inner Loop Header: Depth=1
    movl    %eax, %edx
    movl    %ecx, %eax
    addl    %edx, %eax
    decl    %edi
    movl    %edx, %ecx
    cmpl    $2, %edi
    jg  LBB1_2
LBB1_3:
    popq    %rbp
    retq
    .cfi_endproc
                                        ## -- End function
.subsections_via_symbols