#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*/ fgets(char *, int, int /*<<< orphan*/);
int /*<<< orphan*/ printf(char *, char);
int /*<<< orphan*/ stdin;
int strlen(char *);
int main() {
  int i, j;
  char s[100];
  fgets(s, 100, stdin);
  j = strlen(s) - 1;
  for (i = 0; j >= i; j--) {
    printf("%c", s[j]);
  }
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x70,%rsp
movl   $0x0,-0x4(%rbp)
lea    -0x70(%rbp),%rdi
mov    0x2e9e(%rip),%rax
mov    (%rax),%edx
mov    $0x64,%esi
call   1050 <fgets@plt>
lea    -0x70(%rbp),%rdi
call   1030 <strlen@plt>
sub    $0x1,%eax
mov    %eax,-0xc(%rbp)
movl   $0x0,-0x8(%rbp)
mov    -0xc(%rbp),%eax
cmp    -0x8(%rbp),%eax
jl     119b <main+0x6b>
movslq -0xc(%rbp),%rax
lea    0xe7d(%rip),%rdi
movsbl -0x70(%rbp,%rax,1),%esi
call   1040 <printf@plt>
mov    -0xc(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,-0xc(%rbp)
jmp    116c <main+0x3c>
mov    -0x4(%rbp),%eax
add    $0x70,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %r14
push   %rbx
sub    $0x68,%rsp
mov    0x2eaa(%rip),%rax
mov    (%rax),%edx
mov    %rsp,%rbx
mov    %rbx,%rdi
mov    $0x64,%esi
call   1050 <fgets@plt>
mov    %rbx,%rdi
call   1030 <strlen@plt>
test   %eax,%eax
jle    1189 <main+0x59>
mov    %eax,%ebx
add    $0x1,%rbx
lea    0xe97(%rip),%r14
nopl   0x0(%rax)
lea    -0x2(%rbx),%eax
movsbl (%rsp,%rax,1),%esi
mov    %r14,%rdi
call   1040 <printf@plt>
add    $0xffffffffffffffff,%rbx
cmp    $0x1,%rbx
ja     1170 <main+0x40>
xor    %eax,%eax
add    $0x68,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
@stdin = global i32 0
@.str = [3 x i8] c"%c\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca [100 x i8]
store i32 0, i32* %1
%5 = getelementptr inbounds [100 x i8], [100 x i8]* %4, i64 0, i64 0
%6 = load i32, i32* @stdin
%7 = call i32 @fgets(i8* %5, i32 100, i32 %6)
%8 = getelementptr inbounds [100 x i8], [100 x i8]* %4, i64 0, i64 0
%9 = call i32 @strlen(i8* %8)
%10 = sub nsw i32 %9, 1
store i32 %10, i32* %3
store i32 0, i32* %2
br label %11
11: ; preds = %21, %0
%12 = load i32, i32* %3
%13 = load i32, i32* %2
%14 = icmp sge i32 %12, %13
br i1 %14, label %15, label %24
15: ; preds = %11
%16 = load i32, i32* %3
%17 = sext i32 %16 to i64
%18 = getelementptr inbounds [100 x i8], [100 x i8]* %4, i64 0, i64 %17
%19 = load i8, i8* %18
%20 = call i32 @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i8 signext %19)
br label %21
21: ; preds = %15
%22 = load i32, i32* %3
%23 = add nsw i32 %22, -1
store i32 %23, i32* %3
br label %11
24: ; preds = %11
%25 = load i32, i32* %1
ret i32 %25
}

LLVM IR (-O2):
@stdin = global i32 0
@.str = [3 x i8] c"%c\00"
define i32 @main() {
%1 = alloca [100 x i8]
%2 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 0
%3 = load i32, i32* @stdin
%4 = call i32 @fgets(i8* %2, i32 100, i32 %3)
%5 = call i32 @strlen(i8* %2)
%6 = icmp sgt i32 %5, 0
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 ], [ %11, %9 ]
%11 = add nsw i64 %10, -1
%12 = and i64 %11, 4294967295
%13 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 %12
%14 = load i8, i8* %13
%15 = call i32 @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i8 signext %14)
%16 = icmp ugt i64 %10, 1
br i1 %16, label %9, label %17
17: ; preds = %9, %0
ret i32 0
}