int main(void) {
  int t = 0;
  while (t < 20)
    printf("fib(%d)=%d\n", t, fib(t)), ++t;
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
movl   $0x0,-0x4(%rbp)
movl   $0x0,-0x8(%rbp)
cmpl   $0x14,-0x8(%rbp)
jge    1171 <main+0x51>
mov    -0x8(%rbp),%eax
mov    %eax,-0xc(%rbp)
mov    -0x8(%rbp),%edi
mov    $0x0,%al
call   1040 <fib@plt>
mov    -0xc(%rbp),%esi
mov    %eax,%edx
lea    0xea4(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
mov    -0x8(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x8(%rbp)
jmp    1136 <main+0x16>
xor    %eax,%eax
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
xor    %edi,%edi
xor    %eax,%eax
call   1040 <fib@plt>
lea    0xecf(%rip),%rbx
mov    %rbx,%rdi
xor    %esi,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x1,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x1,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x2,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x2,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x3,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x3,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x4,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x4,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x5,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x5,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x6,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x6,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x7,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x7,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x8,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x8,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x9,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x9,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xa,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xa,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xb,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xb,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xc,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xc,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xd,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xd,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xe,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xe,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xf,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0xf,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x10,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x10,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x11,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x11,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x12,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x12,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x13,%edi
xor    %eax,%eax
call   1040 <fib@plt>
mov    %rbx,%rdi
mov    $0x13,%esi
mov    %eax,%edx
xor    %eax,%eax
call   1030 <printf@plt>
xor    %eax,%eax
pop    %rbx
ret

LLVM IR (-O0):
@.str = [12 x i8] c"fib(%d)=%d\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
store i32 0, i32* %1
store i32 0, i32* %2
br label %3
3: ; preds = %6, %0
%4 = load i32, i32* %2
%5 = icmp slt i32 %4, 20
br i1 %5, label %6, label %13
6: ; preds = %3
%7 = load i32, i32* %2
%8 = load i32, i32* %2
%9 = call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 %8)
%10 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 %7, i32 %9)
%11 = load i32, i32* %2
%12 = add nsw i32 %11, 1
store i32 %12, i32* %2
br label %3
13: ; preds = %3
ret i32 0
}

LLVM IR (-O2):
@.str = [12 x i8] c"fib(%d)=%d\0A\00"
define i32 @main() {
%1 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 0)
%2 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 0, i32 %1)
%3 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 1)
%4 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 1, i32 %3)
%5 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 2)
%6 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 2, i32 %5)
%7 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 3)
%8 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 3, i32 %7)
%9 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 4)
%10 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 4, i32 %9)
%11 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 5)
%12 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 5, i32 %11)
%13 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 6)
%14 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 6, i32 %13)
%15 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 7)
%16 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 7, i32 %15)
%17 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 8)
%18 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 8, i32 %17)
%19 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 9)
%20 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 9, i32 %19)
%21 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 10)
%22 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 10, i32 %21)
%23 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 11)
%24 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 11, i32 %23)
%25 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 12)
%26 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 12, i32 %25)
%27 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 13)
%28 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 13, i32 %27)
%29 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 14)
%30 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 14, i32 %29)
%31 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 15)
%32 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 15, i32 %31)
%33 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 16)
%34 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 16, i32 %33)
%35 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 17)
%36 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 17, i32 %35)
%37 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 18)
%38 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 18, i32 %37)
%39 = tail call i32 (i32, ...) bitcast (i32 (...)* @fib to i32 (i32, ...)*)(i32 19)
%40 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @.str, i64 0, i64 0), i32 19, i32 %39)
ret i32 0
}