#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 */
typedef int uint32_t;

/* Variables and functions */
int popcnt32(uint32_t v) {
  v = (v & 0x55555555) + ((v >> 1) & 0x55555555);
  v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
  v = (v & 0x0f0f0f0f) + ((v >> 4) & 0x0f0f0f0f);
  v = (v & 0x00ff00ff) + ((v >> 8) & 0x00ff00ff);
  v = (v & 0x0000ffff) + ((v >> 16) & 0x0000ffff);
  return (int)v;
}


x86 assembly (clang, -O0):
<popcnt32>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0x4(%rbp)
mov    -0x4(%rbp),%eax
and    $0x55555555,%eax
mov    -0x4(%rbp),%ecx
sar    $0x1,%ecx
and    $0x55555555,%ecx
add    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
and    $0x33333333,%eax
mov    -0x4(%rbp),%ecx
sar    $0x2,%ecx
and    $0x33333333,%ecx
add    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
and    $0xf0f0f0f,%eax
mov    -0x4(%rbp),%ecx
sar    $0x4,%ecx
and    $0xf0f0f0f,%ecx
add    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
and    $0xff00ff,%eax
mov    -0x4(%rbp),%ecx
sar    $0x8,%ecx
and    $0xff00ff,%ecx
add    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
and    $0xffff,%eax
mov    -0x4(%rbp),%ecx
sar    $0x10,%ecx
and    $0xffff,%ecx
add    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<popcnt32>:
mov    %edi,%eax
and    $0x55555555,%eax
shr    %edi
and    $0x55555555,%edi
add    %edi,%eax
mov    %eax,%ecx
and    $0x33333333,%ecx
shr    $0x2,%eax
and    $0x13333333,%eax
add    %ecx,%eax
mov    %eax,%ecx
and    $0x7070707,%ecx
shr    $0x4,%eax
and    $0x7070707,%eax
add    %ecx,%eax
mov    %eax,%ecx
and    $0xf000f,%ecx
shr    $0x8,%eax
and    $0xf000f,%eax
add    %ecx,%eax
movzwl %ax,%ecx
shr    $0x10,%eax
add    %ecx,%eax
ret

LLVM IR (-O0):
define i32 @popcnt32(i32 %0) {
%2 = alloca i32
store i32 %0, i32* %2
%3 = load i32, i32* %2
%4 = and i32 %3, 1431655765
%5 = load i32, i32* %2
%6 = ashr i32 %5, 1
%7 = and i32 %6, 1431655765
%8 = add nsw i32 %4, %7
store i32 %8, i32* %2
%9 = load i32, i32* %2
%10 = and i32 %9, 858993459
%11 = load i32, i32* %2
%12 = ashr i32 %11, 2
%13 = and i32 %12, 858993459
%14 = add nsw i32 %10, %13
store i32 %14, i32* %2
%15 = load i32, i32* %2
%16 = and i32 %15, 252645135
%17 = load i32, i32* %2
%18 = ashr i32 %17, 4
%19 = and i32 %18, 252645135
%20 = add nsw i32 %16, %19
store i32 %20, i32* %2
%21 = load i32, i32* %2
%22 = and i32 %21, 16711935
%23 = load i32, i32* %2
%24 = ashr i32 %23, 8
%25 = and i32 %24, 16711935
%26 = add nsw i32 %22, %25
store i32 %26, i32* %2
%27 = load i32, i32* %2
%28 = and i32 %27, 65535
%29 = load i32, i32* %2
%30 = ashr i32 %29, 16
%31 = and i32 %30, 65535
%32 = add nsw i32 %28, %31
store i32 %32, i32* %2
%33 = load i32, i32* %2
ret i32 %33
}

LLVM IR (-O2):
define i32 @popcnt32(i32 %0) {
%2 = and i32 %0, 1431655765
%3 = lshr i32 %0, 1
%4 = and i32 %3, 1431655765
%5 = add nuw nsw i32 %4, %2
%6 = and i32 %5, 858993459
%7 = lshr i32 %5, 2
%8 = and i32 %7, 322122547
%9 = add nuw nsw i32 %8, %6
%10 = and i32 %9, 117901063
%11 = lshr i32 %9, 4
%12 = and i32 %11, 117901063
%13 = add nuw nsw i32 %12, %10
%14 = and i32 %13, 983055
%15 = lshr i32 %13, 8
%16 = and i32 %15, 983055
%17 = add nuw nsw i32 %16, %14
%18 = and i32 %17, 31
%19 = lshr i32 %17, 16
%20 = add nuw nsw i32 %18, %19
ret i32 %20
}