#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*/ scanf(char *, char *);
int strlen(char *);
int main(void) {
  int x, i;
  char word[40];
  printf("Enter a word:\n");
  scanf("%s", word);
  x = strlen(word);
  for (i = x; i >= 0; i--)
    printf("%c", word[i]);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x40,%rsp
movl   $0x0,-0x4(%rbp)
lea    0xeba(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
lea    -0x40(%rbp),%rsi
lea    0xeb7(%rip),%rdi
call   1050 <scanf@plt>
lea    -0x40(%rbp),%rdi
call   1030 <strlen@plt>
mov    %eax,-0x8(%rbp)
mov    -0x8(%rbp),%eax
mov    %eax,-0xc(%rbp)
cmpl   $0x0,-0xc(%rbp)
jl     119e <main+0x6e>
movslq -0xc(%rbp),%rax
movsbl -0x40(%rbp,%rax,1),%esi
lea    0xe89(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
mov    -0xc(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,-0xc(%rbp)
jmp    116f <main+0x3f>
xor    %eax,%eax
add    $0x40,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
sub    $0x30,%rsp
lea    0xeb7(%rip),%rdi
call   1040 <puts@plt>
lea    0xea8(%rip),%rdi
mov    %rsp,%rbx
mov    %rbx,%rsi
call   1060 <scanf@plt>
mov    %rbx,%rdi
call   1050 <strlen@plt>
test   %eax,%eax
js     118f <main+0x4f>
mov    %eax,%ebx
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax,%rax,1)
movsbl (%rsp,%rbx,1),%edi
call   1030 <putchar@plt>
add    $0xffffffffffffffff,%rbx
jb     1180 <main+0x40>
xor    %eax,%eax
add    $0x30,%rsp
pop    %rbx
ret

LLVM IR (-O0):
@.str = [15 x i8] c"Enter a word:\0A\00"
@.str.1 = [3 x i8] c"%s\00"
@.str.2 = [3 x i8] c"%c\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca [40 x i8]
store i32 0, i32* %1
%5 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([15 x i8], [15 x i8]* @.str, i64 0, i64 0))
%6 = getelementptr inbounds [40 x i8], [40 x i8]* %4, i64 0, i64 0
%7 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8* %6)
%8 = getelementptr inbounds [40 x i8], [40 x i8]* %4, i64 0, i64 0
%9 = call i32 @strlen(i8* %8)
store i32 %9, i32* %2
%10 = load i32, i32* %2
store i32 %10, i32* %3
br label %11
11: ; preds = %21, %0
%12 = load i32, i32* %3
%13 = icmp sge i32 %12, 0
br i1 %13, label %14, label %24
14: ; preds = %11
%15 = load i32, i32* %3
%16 = sext i32 %15 to i64
%17 = getelementptr inbounds [40 x i8], [40 x i8]* %4, i64 0, i64 %16
%18 = load i8, i8* %17
%19 = sext i8 %18 to i32
%20 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.2, i64 0, i64 0), i32 %19)
br label %21
21: ; preds = %14
%22 = load i32, i32* %3
%23 = add nsw i32 %22, -1
store i32 %23, i32* %3
br label %11
24: ; preds = %11
ret i32 0
}

LLVM IR (-O2):
@.str.1 = [3 x i8] c"%s\00"
@str = [14 x i8] c"Enter a word:\00"
define i32 @main() {
%1 = alloca [40 x i8]
%2 = getelementptr inbounds [40 x i8], [40 x i8]* %1, i64 0, i64 0
%3 = tail call i32 @puts(i8* dereferenceable(1) getelementptr inbounds ([14 x i8], [14 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 = icmp sgt i32 %5, -1
br i1 %6, label %7, label %17
7: ; preds = %0
%8 = zext i32 %5 to i64
br label %9
9: ; preds = %7, %9
%10 = phi i64 [ %8, %7 ], [ %15, %9 ]
%11 = getelementptr inbounds [40 x i8], [40 x i8]* %1, i64 0, i64 %10
%12 = load i8, i8* %11
%13 = sext i8 %12 to i32
%14 = call i32 @putchar(i32 %13)
%15 = add nsw i64 %10, -1
%16 = icmp eq i64 %10, 0
br i1 %16, label %17, label %9
17: ; preds = %9, %0
ret i32 0
}