#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 *, int *);
int main() {
  int n, i, S;
  printf("Input natural number n: \n");
  scanf("%d", &n);
  S = 0;
  i = 0;
  while (i <= n) {
    S += i;
    i++;
  }
  printf("Sum of first n nubers is %d\n", S);
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
movl   $0x0,-0x4(%rbp)
lea    0xeca(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
lea    0xed6(%rip),%rdi
lea    -0x8(%rbp),%rsi
call   1040 <scanf@plt>
movl   $0x0,-0x10(%rbp)
movl   $0x0,-0xc(%rbp)
mov    -0xc(%rbp),%eax
cmp    -0x8(%rbp),%eax
jg     117e <main+0x5e>
mov    -0xc(%rbp),%eax
add    -0x10(%rbp),%eax
mov    %eax,-0x10(%rbp)
mov    -0xc(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0xc(%rbp)
jmp    115b <main+0x3b>
mov    -0x10(%rbp),%esi
lea    0xe95(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
mov    -0x4(%rbp),%eax
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rax
lea    0xee8(%rip),%rdi
call   1030 <puts@plt>
lea    0xebc(%rip),%rdi
lea    0x4(%rsp),%rsi
call   1050 <scanf@plt>
mov    0x4(%rsp),%eax
lea    -0x1(%rax),%esi
imul   %rax,%rsi
shr    %rsi
add    %eax,%esi
xor    %ecx,%ecx
test   %eax,%eax
cmovs  %ecx,%esi
lea    0xe97(%rip),%rdi
xor    %eax,%eax
call   1040 <printf@plt>
xor    %eax,%eax
pop    %rcx
ret

LLVM IR (-O0):
@.str = [26 x i8] c"Input natural number n: \0A\00"
@.str.1 = [3 x i8] c"%d\00"
@.str.2 = [29 x i8] c"Sum of first n nubers is %d\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca i32
store i32 0, i32* %1
%5 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([26 x i8], [26 x i8]* @.str, i64 0, i64 0))
%6 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.1, i64 0, i64 0), i32* %2)
store i32 0, i32* %4
store i32 0, i32* %3
br label %7
7: ; preds = %11, %0
%8 = load i32, i32* %3
%9 = load i32, i32* %2
%10 = icmp sle i32 %8, %9
br i1 %10, label %11, label %17
11: ; preds = %7
%12 = load i32, i32* %3
%13 = load i32, i32* %4
%14 = add nsw i32 %13, %12
store i32 %14, i32* %4
%15 = load i32, i32* %3
%16 = add nsw i32 %15, 1
store i32 %16, i32* %3
br label %7
17: ; preds = %7
%18 = load i32, i32* %4
%19 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([29 x i8], [29 x i8]* @.str.2, i64 0, i64 0), i32 %18)
%20 = load i32, i32* %1
ret i32 %20
}

LLVM IR (-O2):
@.str.1 = [3 x i8] c"%d\00"
@.str.2 = [29 x i8] c"Sum of first n nubers is %d\0A\00"
@str = [25 x i8] c"Input natural number n: \00"
define i32 @main() {
%1 = alloca i32
%2 = bitcast i32* %1 to i8*
%3 = tail call i32 @puts(i8* dereferenceable(1) getelementptr inbounds ([25 x i8], [25 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), i32* %1)
%5 = load i32, i32* %1
%6 = icmp slt i32 %5, 0
%7 = zext i32 %5 to i33
%8 = add nsw i32 %5, -1
%9 = zext i32 %8 to i33
%10 = mul i33 %7, %9
%11 = lshr i33 %10, 1
%12 = trunc i33 %11 to i32
%13 = add i32 %5, %12
%14 = select i1 %6, i32 0, i32 %13
%15 = call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([29 x i8], [29 x i8]* @.str.2, i64 0, i64 0), i32 %14)
ret i32 0
}