#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 */
scalar_t__ isnan(double const);
int check_nan(const double *const arr, int n) {
  for (int i = 0; i < n; ++i)
    if (isnan(arr[i]))
      return i;
  return -1;
}


x86 assembly (clang, -O0):
<check_nan>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x10(%rbp)
mov    %esi,-0x14(%rbp)
movl   $0x0,-0x18(%rbp)
mov    -0x18(%rbp),%eax
cmp    -0x14(%rbp),%eax
jge    116c <check_nan+0x5c>
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
call   1030 <isnan@plt>
cmp    $0x0,%rax
je     1159 <check_nan+0x49>
mov    -0x18(%rbp),%eax
mov    %eax,-0x4(%rbp)
jmp    1173 <check_nan+0x63>
jmp    115e <check_nan+0x4e>
mov    -0x18(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x18(%rbp)
jmp    1126 <check_nan+0x16>
movl   $0xffffffff,-0x4(%rbp)
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<check_nan>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
mov    $0xffffffff,%r14d
test   %esi,%esi
jle    114e <check_nan+0x3e>
mov    %rdi,%r15
mov    %esi,%ebx
xor    %ebp,%ebp
nopl   0x0(%rax,%rax,1)
movsd  (%r15,%rbp,8),%xmm0
call   1030 <isnan@plt>
test   %rax,%rax
jne    114b <check_nan+0x3b>
add    $0x1,%rbp
cmp    %rbp,%rbx
jne    1130 <check_nan+0x20>
jmp    114e <check_nan+0x3e>
mov    %ebp,%r14d
mov    %r14d,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret

LLVM IR (-O0):
define i32 @check_nan(double* %0, i32 %1) {
%3 = alloca i32
%4 = alloca double*
%5 = alloca i32
%6 = alloca i32
store double* %0, double** %4
store i32 %1, i32* %5
store i32 0, i32* %6
br label %7
7: ; preds = %22, %2
%8 = load i32, i32* %6
%9 = load i32, i32* %5
%10 = icmp slt i32 %8, %9
br i1 %10, label %11, label %25
11: ; preds = %7
%12 = load double*, double** %4
%13 = load i32, i32* %6
%14 = sext i32 %13 to i64
%15 = getelementptr inbounds double, double* %12, i64 %14
%16 = load double, double* %15
%17 = call i64 @isnan(double %16)
%18 = icmp ne i64 %17, 0
br i1 %18, label %19, label %21
19: ; preds = %11
%20 = load i32, i32* %6
store i32 %20, i32* %3
br label %26
21: ; preds = %11
br label %22
22: ; preds = %21
%23 = load i32, i32* %6
%24 = add nsw i32 %23, 1
store i32 %24, i32* %6
br label %7
25: ; preds = %7
store i32 -1, i32* %3
br label %26
26: ; preds = %25, %19
%27 = load i32, i32* %3
ret i32 %27
}

LLVM IR (-O2):
define i32 @check_nan(double* nocapture %0, i32 %1) {
%3 = icmp sgt i32 %1, 0
br i1 %3, label %4, label %17
4: ; preds = %2
%5 = zext i32 %1 to i64
br label %6
6: ; preds = %4, %12
%7 = phi i64 [ 0, %4 ], [ %13, %12 ]
%8 = getelementptr inbounds double, double* %0, i64 %7
%9 = load double, double* %8
%10 = tail call i64 @isnan(double %9)
%11 = icmp eq i64 %10, 0
br i1 %11, label %12, label %15
12: ; preds = %6
%13 = add nuw nsw i64 %7, 1
%14 = icmp eq i64 %13, %5
br i1 %14, label %17, label %6
15: ; preds = %6
%16 = trunc i64 %7 to i32
br label %17
17: ; preds = %12, %15, %2
%18 = phi i32 [ -1, %2 ], [ %16, %15 ], [ -1, %12 ]
ret i32 %18
}