_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
Parameter |
Description |
[in] v1 |
The first parameter to multiply. |
[in] v2 |
The second parameter to multiply. |
[in] imm8 |
A constant that indicates which halves of the input parameters to use as operands. |
Return value
The product calculated by multiplying 64 bits of v1 and 64 bits of v2.
Requirements
Intrinsic |
Architecture |
_mm_clmulepi64_si128 |
x86, x64 |
Header file <wmmintrin.h>
Remarks
Use the following table to determine which halves of v1 and v2 are used to calculate the product.
Bit 4 of imm8 |
Bit 0 of imm8 |
Product |
|---|---|---|
0 |
0 |
v1[63:0] * v2[63:0] |
0 |
1 |
v1[127:64] * v2[63:0] |
1 |
0 |
v1[63:0] * v2[127:64] |
1 |
1 |
v1[127:64] * v2[127:64] |
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