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_mm_popcnt_u64

Visual Studio 2010

Microsoft Specific

Emits the Streaming SIMD Extensions 4 (SSE4) instruction popcnt. This instruction calculates the number of bits of the parameter that are set to 1.

Copy 
int _mm_popcnt_u64 (
   unsigned __int64 a
);

Parameter

Description

[in] a

An integer.

The number of bits set to one in a.

Intrinsic

Architecture

_mm_popcnt_u64

x64

Header file <nmmintrin.h>

Before you use this intrinsic, software must ensure that the processor supports the instruction.

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#include <stdio.h>
#include <nmmintrin.h>

int main ()
{
    unsigned __int64 a = 0x123456789ABCDEF0;

    int res = _mm_popcnt_u64(a);

    printf_s("Result res should be 32: %d\n", res);

    return 0;
}

Result res should be 32: 32

Reference

__m64
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Return value type inconsistency?
Code and documentation appear to be out of sync. Should the return value be an __int64 per nmmintrin.h?
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