#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
int /*<<< orphan*/ gets(char *);
int /*<<< orphan*/ printf(char *, ...);
int strlen(char *);
main() {
  int i, f;
  char frase[30];
  printf("Entre com uma frase: ");
  gets(frase);
  f = strlen(frase) - 1;
  for (i = f; i >= 0; --i) {
    printf("%c", frase[i]);
  }
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
movl   $0x0,-0x4(%rbp)
lea    0xeba(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
lea    -0x30(%rbp),%rdi
call   1050 <gets@plt>
lea    -0x30(%rbp),%rdi
call   1030 <strlen@plt>
sub    $0x1,%eax
mov    %eax,-0xc(%rbp)
mov    -0xc(%rbp),%eax
mov    %eax,-0x8(%rbp)
cmpl   $0x0,-0x8(%rbp)
jl     119a <main+0x6a>
movslq -0x8(%rbp),%rax
movsbl -0x30(%rbp,%rax,1),%esi
lea    0xe91(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
mov    -0x8(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,-0x8(%rbp)
jmp    116b <main+0x3b>
mov    -0x4(%rbp),%eax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
sub    $0x20,%rsp
lea    0xeb4(%rip),%rdi
xor    %eax,%eax
call   1050 <printf@plt>
mov    %rsp,%rbx
mov    %rbx,%rdi
call   1060 <gets@plt>
mov    %rbx,%rdi
call   1040 <strlen@plt>
test   %eax,%eax
jle    1186 <main+0x46>
mov    %eax,%ebx
add    $0x1,%rbx
lea    -0x2(%rbx),%eax
movsbl (%rsp,%rax,1),%edi
call   1030 <putchar@plt>
add    $0xffffffffffffffff,%rbx
cmp    $0x1,%rbx
ja     1170 <main+0x30>
xor    %eax,%eax
add    $0x20,%rsp
pop    %rbx
ret

LLVM IR (-O0):
@.str = [22 x i8] c"Entre com uma frase: \00"
@.str.1 = [3 x i8] c"%c\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca [30 x i8]
store i32 0, i32* %1
%5 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.str, i64 0, i64 0))
%6 = getelementptr inbounds [30 x i8], [30 x i8]* %4, i64 0, i64 0
%7 = call i32 @gets(i8* %6)
%8 = getelementptr inbounds [30 x i8], [30 x i8]* %4, i64 0, i64 0
%9 = call i32 @strlen(i8* %8)
%10 = sub nsw i32 %9, 1
store i32 %10, i32* %3
%11 = load i32, i32* %3
store i32 %11, i32* %2
br label %12
12: ; preds = %22, %0
%13 = load i32, i32* %2
%14 = icmp sge i32 %13, 0
br i1 %14, label %15, label %25
15: ; preds = %12
%16 = load i32, i32* %2
%17 = sext i32 %16 to i64
%18 = getelementptr inbounds [30 x i8], [30 x i8]* %4, i64 0, i64 %17
%19 = load i8, i8* %18
%20 = sext i8 %19 to i32
%21 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i32 %20)
br label %22
22: ; preds = %15
%23 = load i32, i32* %2
%24 = add nsw i32 %23, -1
store i32 %24, i32* %2
br label %12
25: ; preds = %12
%26 = load i32, i32* %1
ret i32 %26
}

LLVM IR (-O2):
@.str = [22 x i8] c"Entre com uma frase: \00"
define i32 @main() {
%1 = alloca [30 x i8]
%2 = getelementptr inbounds [30 x i8], [30 x i8]* %1, i64 0, i64 0
%3 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([22 x i8], [22 x i8]* @.str, i64 0, i64 0))
%4 = call i32 @gets(i8* %2)
%5 = call i32 @strlen(i8* %2)
%6 = icmp sgt i32 %5, 0
br i1 %6, label %7, label %18
7: ; preds = %0
%8 = zext i32 %5 to i64
br label %9
9: ; preds = %7, %9
%10 = phi i64 [ %8, %7 ], [ %11, %9 ]
%11 = add nsw i64 %10, -1
%12 = and i64 %11, 4294967295
%13 = getelementptr inbounds [30 x i8], [30 x i8]* %1, i64 0, i64 %12
%14 = load i8, i8* %13
%15 = sext i8 %14 to i32
%16 = call i32 @putchar(i32 %15)
%17 = icmp ugt i64 %10, 1
br i1 %17, label %9, label %18
18: ; preds = %9, %0
ret i32 0
}