_mm_clmulepi64_si128

Microsoft Specific

Emits the instruction pclmulqdq. This instruction performs a multiplication of two 64-bit integers. The multiplication does not calculate a carry bit.

__m128i _mm_clmulepi64_si128 (
   __m128i v1,
   __m128i v2,
   const int imm8
);

Parameters

Return value

The product calculated by multiplying 64 bits of v1 and 64 bits of v2.

Requirements

Header file <wmmintrin.h>

Remarks

Use the following table to determine which halves of v1 and v2 are used to calculate the product.

Example

#include <wmmintrin.h>
#include <stdio.h>

int main()
{
    __m128i a;
    __m128i b;

    a.m128i_i64[1] = 2;
    a.m128i_i64[0] = -1284;
    b.m128i_i64[1] = 25;
    b.m128i_i64[0] = 65535;

    // _mm_clmulepi64_si128 only looks at the least significant bit of each
    // hexadecimal integer
    const int product1 = 0x11;
    const int product2 = 0x00;
    const int product3 = 0xF2;

    int expect1 = int ( a.m128i_i64[1] * b.m128i_i64[1] );
    int expect2 = int ( a.m128i_i64[0] * b.m128i_i64[0] );
    int expect3 = int ( a.m128i_i64[0] * b.m128i_i64[1] );

    __m128i result1 = _mm_clmulepi64_si128( a, b, product1 );
    __m128i result2 = _mm_clmulepi64_si128( a, b, product2 );
    __m128i result3 = _mm_clmulepi64_si128( a, b, product3 );

    printf_s("%I64d times %I64d without a carry bit: %I64d\n", 
        a.m128i_i64[1], b.m128i_i64[1], result1.m128i_i64[0]);
    printf_s("%I64d times %I64d without a carry bit: %I64d\n", 
        a.m128i_i64[0], b.m128i_i64[0], result2.m128i_i64[0]);
    printf_s("%I64d times %I64d without a carry bit: %I64d\n", 
        a.m128i_i64[0], b.m128i_i64[1], result3.m128i_i64[0]);

    return 0;
}

2 times 25 without a carry bit: 50 -1284 times 65535 without a carry bit: 50419284 -1284 times 25 without a carry bit: -32036

See Also

Reference

Compiler Intrinsics

Change History