#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 *);
int main() {
  char a[100], temp;
  int i = 0, j = 0;
  printf("Enter words: \n");
  gets(a);
  j = strlen(a) - 1;
  for (i; i < j; i++) {
    temp = a[i];
    a[i] = a[j];
    a[j] = temp;
    j--;
  }
  printf("%s", a);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x80,%rsp
movl   $0x0,-0x4(%rbp)
movl   $0x0,-0x78(%rbp)
movl   $0x0,-0x7c(%rbp)
lea    0xea9(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
lea    -0x70(%rbp),%rdi
call   1050 <gets@plt>
lea    -0x70(%rbp),%rdi
call   1030 <strlen@plt>
sub    $0x1,%eax
mov    %eax,-0x7c(%rbp)
mov    -0x78(%rbp),%eax
cmp    -0x7c(%rbp),%eax
jge    11bf <main+0x8f>
movslq -0x78(%rbp),%rax
mov    -0x70(%rbp,%rax,1),%al
mov    %al,-0x71(%rbp)
movslq -0x7c(%rbp),%rax
mov    -0x70(%rbp,%rax,1),%cl
movslq -0x78(%rbp),%rax
mov    %cl,-0x70(%rbp,%rax,1)
mov    -0x71(%rbp),%cl
movslq -0x7c(%rbp),%rax
mov    %cl,-0x70(%rbp,%rax,1)
mov    -0x7c(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,-0x7c(%rbp)
mov    -0x78(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x78(%rbp)
jmp    1176 <main+0x46>
lea    -0x70(%rbp),%rsi
lea    0xe45(%rip),%rdi
mov    $0x0,%al
call   1040 <printf@plt>
xor    %eax,%eax
add    $0x80,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
sub    $0x70,%rsp
lea    0xeb7(%rip),%rdi
call   1030 <puts@plt>
mov    %rsp,%rbx
mov    %rbx,%rdi
call   1060 <gets@plt>
mov    %rbx,%rdi
call   1040 <strlen@plt>
cmp    $0x2,%eax
jl     11a0 <main+0x60>
mov    %eax,%eax
add    $0xfffffffffffffffe,%rax
xor    %ecx,%ecx
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax,%rax,1)
movzbl (%rsp,%rcx,1),%edx
movzbl 0x1(%rsp,%rax,1),%ebx
mov    %bl,(%rsp,%rcx,1)
mov    %dl,0x1(%rsp,%rax,1)
add    $0x1,%rcx
lea    -0x1(%rax),%rdx
cmp    %rax,%rcx
mov    %rdx,%rax
jl     1180 <main+0x40>
lea    0xe59(%rip),%rdi
mov    %rsp,%rsi
xor    %eax,%eax
call   1050 <printf@plt>
xor    %eax,%eax
add    $0x70,%rsp
pop    %rbx
ret

LLVM IR (-O0):
@.str = [15 x i8] c"Enter words: \0A\00"
@.str.1 = [3 x i8] c"%s\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca [100 x i8]
%3 = alloca i8
%4 = alloca i32
%5 = alloca i32
store i32 0, i32* %1
store i32 0, i32* %4
store i32 0, i32* %5
%6 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([15 x i8], [15 x i8]* @.str, i64 0, i64 0))
%7 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 0
%8 = call i32 @gets(i8* %7)
%9 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 0
%10 = call i32 @strlen(i8* %9)
%11 = sub nsw i32 %10, 1
store i32 %11, i32* %5
%12 = load i32, i32* %4
br label %13
13: ; preds = %35, %0
%14 = load i32, i32* %4
%15 = load i32, i32* %5
%16 = icmp slt i32 %14, %15
br i1 %16, label %17, label %38
17: ; preds = %13
%18 = load i32, i32* %4
%19 = sext i32 %18 to i64
%20 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 %19
%21 = load i8, i8* %20
store i8 %21, i8* %3
%22 = load i32, i32* %5
%23 = sext i32 %22 to i64
%24 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 %23
%25 = load i8, i8* %24
%26 = load i32, i32* %4
%27 = sext i32 %26 to i64
%28 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 %27
store i8 %25, i8* %28
%29 = load i8, i8* %3
%30 = load i32, i32* %5
%31 = sext i32 %30 to i64
%32 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 %31
store i8 %29, i8* %32
%33 = load i32, i32* %5
%34 = add nsw i32 %33, -1
store i32 %34, i32* %5
br label %35
35: ; preds = %17
%36 = load i32, i32* %4
%37 = add nsw i32 %36, 1
store i32 %37, i32* %4
br label %13
38: ; preds = %13
%39 = getelementptr inbounds [100 x i8], [100 x i8]* %2, i64 0, i64 0
%40 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8* %39)
ret i32 0
}

LLVM IR (-O2):
@.str.1 = [3 x i8] c"%s\00"
@str = [14 x i8] c"Enter words: \00"
define i32 @main() {
%1 = alloca [100 x i8]
%2 = getelementptr inbounds [100 x i8], [100 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 @gets(i8* %2)
%5 = call i32 @strlen(i8* %2)
%6 = icmp sgt i32 %5, 1
br i1 %6, label %7, label %20
7: ; preds = %0
%8 = zext i32 %5 to i64
%9 = add nsw i64 %8, -1
br label %10
10: ; preds = %7, %10
%11 = phi i64 [ 0, %7 ], [ %17, %10 ]
%12 = phi i64 [ %9, %7 ], [ %18, %10 ]
%13 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 %11
%14 = load i8, i8* %13
%15 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 %12
%16 = load i8, i8* %15
store i8 %16, i8* %13
store i8 %14, i8* %15
%17 = add nuw nsw i64 %11, 1
%18 = add nsw i64 %12, -1
%19 = icmp slt i64 %17, %18
br i1 %19, label %10, label %20
20: ; preds = %10, %0
%21 = call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i8* %2)
ret i32 0
}