#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() {
  int slen;
  char str[20];
  printf("Input string:");
  scanf("%s", &str);
  slen = strlen(str);
  reverse(str, 0, slen - 1);
  printf("\nRev String= %s\n", str);
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
lea    0xeb1(%rip),%rdi
mov    $0x0,%al
call   1050 <printf@plt>
lea    -0x20(%rbp),%rsi
lea    0xead(%rip),%rdi
call   1060 <scanf@plt>
lea    -0x20(%rbp),%rdi
call   1040 <strlen@plt>
mov    %eax,-0x4(%rbp)
lea    -0x20(%rbp),%rdi
mov    -0x4(%rbp),%edx
sub    $0x1,%edx
xor    %esi,%esi
call   1030 <reverse@plt>
lea    -0x20(%rbp),%rsi
lea    0xe83(%rip),%rdi
mov    $0x0,%al
call   1050 <printf@plt>
xor    %eax,%eax
add    $0x20,%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    0xeb4(%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    0xe90(%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 = [14 x i8] c"Input string:\00"
@.str.1 = [3 x i8] c"%s\00"
@.str.2 = [17 x i8] c"\0ARev String= %s\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca [20 x i8]
%3 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str, i64 0, i64 0))
%4 = bitcast [20 x i8]* %2 to i8**
%5 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8** %4)
%6 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%7 = call i32 @strlen(i8* %6)
store i32 %7, i32* %1
%8 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%9 = load i32, i32* %1
%10 = sub nsw i32 %9, 1
%11 = call i32 @reverse(i8* %8, i32 0, i32 %10)
%12 = getelementptr inbounds [20 x i8], [20 x i8]* %2, i64 0, i64 0
%13 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str.2, i64 0, i64 0), i8* %12)
ret i32 0
}

LLVM IR (-O2):
@.str = [14 x i8] c"Input string:\00"
@.str.1 = [3 x i8] c"%s\00"
@.str.2 = [17 x i8] c"\0ARev String= %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 ([14 x i8], [14 x i8]* @.str, i64 0, i64 0))
%4 = bitcast [20 x i8]* %1 to i8**
%5 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8** %4)
%6 = call i32 @strlen(i8* %2)
%7 = add nsw i32 %6, -1
%8 = call i32 @reverse(i8* %2, i32 0, i32 %7)
%9 = call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([17 x i8], [17 x i8]* @.str.2, i64 0, i64 0), i8* %2)
ret i32 0
}