#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*/ puts(char *);
int strlen(char *);
int main() {
  char arr[20];
  gets(arr);
  int len;
  len = strlen(arr);
  int i = 0, j = len - 1;
  char temp;
  while (i < j) {
    temp = arr[j];
    arr[j] = arr[i];
    arr[i] = temp;
    i++;
    j--;
  }
  puts(arr);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
movl   $0x0,-0x4(%rbp)
lea    -0x20(%rbp),%rdi
call   1050 <gets@plt>
lea    -0x20(%rbp),%rdi
call   1040 <strlen@plt>
mov    %eax,-0x24(%rbp)
movl   $0x0,-0x28(%rbp)
mov    -0x24(%rbp),%eax
sub    $0x1,%eax
mov    %eax,-0x2c(%rbp)
mov    -0x28(%rbp),%eax
cmp    -0x2c(%rbp),%eax
jge    11ad <main+0x7d>
movslq -0x2c(%rbp),%rax
mov    -0x20(%rbp,%rax,1),%al
mov    %al,-0x2d(%rbp)
movslq -0x28(%rbp),%rax
mov    -0x20(%rbp,%rax,1),%cl
movslq -0x2c(%rbp),%rax
mov    %cl,-0x20(%rbp,%rax,1)
mov    -0x2d(%rbp),%cl
movslq -0x28(%rbp),%rax
mov    %cl,-0x20(%rbp,%rax,1)
mov    -0x28(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x28(%rbp)
mov    -0x2c(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,-0x2c(%rbp)
jmp    1164 <main+0x34>
lea    -0x20(%rbp),%rdi
call   1030 <puts@plt>
xor    %eax,%eax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
sub    $0x20,%rsp
mov    %rsp,%rbx
mov    %rbx,%rdi
call   1050 <gets@plt>
mov    %rbx,%rdi
call   1040 <strlen@plt>
cmp    $0x2,%eax
jl     1180 <main+0x50>
mov    %eax,%eax
add    $0xfffffffffffffffe,%rax
xor    %ecx,%ecx
cs nopw 0x0(%rax,%rax,1)
nop
movzbl 0x1(%rsp,%rax,1),%edx
movzbl (%rsp,%rcx,1),%ebx
mov    %bl,0x1(%rsp,%rax,1)
mov    %dl,(%rsp,%rcx,1)
add    $0x1,%rcx
lea    -0x1(%rax),%rdx
cmp    %rax,%rcx
mov    %rdx,%rax
jl     1160 <main+0x30>
mov    %rsp,%rdi
call   1030 <puts@plt>
xor    %eax,%eax
add    $0x20,%rsp
pop    %rbx
ret

LLVM IR (-O0):
define i32 @main() {
%1 = alloca i32
%2 = alloca [20 x i8]
%3 = alloca i32
%4 = alloca i32
%5 = alloca i32
%6 = alloca i8
store i32 0, i32* %1
%7 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%8 = call i32 @gets(i8* %7)
%9 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%10 = call i32 @strlen(i8* %9)
store i32 %10, i32* %3
store i32 0, i32* %4
%11 = load i32, i32* %3
%12 = sub nsw i32 %11, 1
store i32 %12, i32* %5
br label %13
13: ; preds = %17, %0
%14 = load i32, i32* %4
%15 = load i32, i32* %5
%16 = icmp slt i32 %14, %15
br i1 %16, label %17, label %37
17: ; preds = %13
%18 = load i32, i32* %5
%19 = sext i32 %18 to i64
%20 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 %19
%21 = load i8, i8* %20
store i8 %21, i8* %6
%22 = load i32, i32* %4
%23 = sext i32 %22 to i64
%24 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 %23
%25 = load i8, i8* %24
%26 = load i32, i32* %5
%27 = sext i32 %26 to i64
%28 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 %27
store i8 %25, i8* %28
%29 = load i8, i8* %6
%30 = load i32, i32* %4
%31 = sext i32 %30 to i64
%32 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 %31
store i8 %29, i8* %32
%33 = load i32, i32* %4
%34 = add nsw i32 %33, 1
store i32 %34, i32* %4
%35 = load i32, i32* %5
%36 = add nsw i32 %35, -1
store i32 %36, i32* %5
br label %13
37: ; preds = %13
%38 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%39 = call i32 @puts(i8* %38)
ret i32 0
}

LLVM IR (-O2):
define i32 @main() {
%1 = alloca [20 x i8]
%2 = getelementptr inbounds [20 x i8], [20 x i8]* %1, i64 0, i64 0
%3 = call i32 @gets(i8* %2)
%4 = call i32 @strlen(i8* %2)
%5 = icmp sgt i32 %4, 1
br i1 %5, label %6, label %19
6: ; preds = %0
%7 = zext i32 %4 to i64
%8 = add nsw i64 %7, -1
br label %9
9: ; preds = %6, %9
%10 = phi i64 [ 0, %6 ], [ %16, %9 ]
%11 = phi i64 [ %8, %6 ], [ %17, %9 ]
%12 = getelementptr inbounds [20 x i8], [20 x i8]* %1, i64 0, i64 %11
%13 = load i8, i8* %12
%14 = getelementptr inbounds [20 x i8], [20 x i8]* %1, i64 0, i64 %10
%15 = load i8, i8* %14
store i8 %15, i8* %12
store i8 %13, i8* %14
%16 = add nuw nsw i64 %10, 1
%17 = add nsw i64 %11, -1
%18 = icmp slt i64 %16, %17
br i1 %18, label %9, label %19
19: ; preds = %9, %0
%20 = call i32 @puts(i8* %2)
ret i32 0
}