#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*/ printf(char *, ...);
int /*<<< orphan*/ reverse(char *, int /*<<< orphan*/, int);
int /*<<< orphan*/ scanf(char *, char *);
int strlen(char *);
int main() {
  char str1[20];
  int size;
  printf("Enter a string to reverse: ");
  scanf("%s", str1);
  size = strlen(str1);
  reverse(str1, 0, size - 1);
  printf("The string after reversing is: %s\n", str1);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
movl   $0x0,-0x4(%rbp)
lea    0xeaa(%rip),%rdi
mov    $0x0,%al
call   1050 <printf@plt>
lea    -0x20(%rbp),%rsi
lea    0xeb4(%rip),%rdi
call   1060 <scanf@plt>
lea    -0x20(%rbp),%rdi
call   1040 <strlen@plt>
mov    %eax,-0x24(%rbp)
lea    -0x20(%rbp),%rdi
mov    -0x24(%rbp),%edx
sub    $0x1,%edx
xor    %esi,%esi
call   1030 <reverse@plt>
lea    -0x20(%rbp),%rsi
lea    0xe8a(%rip),%rdi
mov    $0x0,%al
call   1050 <printf@plt>
xor    %eax,%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>
lea    0xec2(%rip),%rdi
mov    %rsp,%rbx
mov    %rbx,%rsi
call   1060 <scanf@plt>
mov    %rbx,%rdi
call   1040 <strlen@plt>
lea    -0x1(%rax),%edx
mov    %rbx,%rdi
xor    %esi,%esi
call   1030 <reverse@plt>
lea    0xe9e(%rip),%rdi
mov    %rbx,%rsi
xor    %eax,%eax
call   1050 <printf@plt>
xor    %eax,%eax
add    $0x20,%rsp
pop    %rbx
ret

LLVM IR (-O0):
@.str = [28 x i8] c"Enter a string to reverse: \00"
@.str.1 = [3 x i8] c"%s\00"
@.str.2 = [35 x i8] c"The string after reversing is: %s\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca [20 x i8]
%3 = alloca i32
store i32 0, i32* %1
%4 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([28 x i8], [28 x i8]* @.str, i64 0, i64 0))
%5 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%6 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8* %5)
%7 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%8 = call i32 @strlen(i8* %7)
store i32 %8, i32* %3
%9 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%10 = load i32, i32* %3
%11 = sub nsw i32 %10, 1
%12 = call i32 @reverse(i8* %9, i32 0, i32 %11)
%13 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%14 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([35 x i8], [35 x i8]* @.str.2, i64 0, i64 0), i8* %13)
ret i32 0
}

LLVM IR (-O2):
@.str = [28 x i8] c"Enter a string to reverse: \00"
@.str.1 = [3 x i8] c"%s\00"
@.str.2 = [35 x i8] c"The string after reversing is: %s\0A\00"
define i32 @main() {
%1 = alloca [20 x i8]
%2 = getelementptr inbounds [20 x i8], [20 x i8]* %1, i64 0, i64 0
%3 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([28 x i8], [28 x i8]* @.str, i64 0, i64 0))
%4 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8* %2)
%5 = call i32 @strlen(i8* %2)
%6 = add nsw i32 %5, -1
%7 = call i32 @reverse(i8* %2, i32 0, i32 %6)
%8 = call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([35 x i8], [35 x i8]* @.str.2, i64 0, i64 0), i8* %2)
ret i32 0
}