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_mm_shuffle_epi8

Microsoft Specific

Emits the Supplemental Streaming SIMD Extensions 3 (SSSE3) instruction pshufb. This instruction shuffles 16-byte parameters from a 128-bit parameter.

__m128i _mm_shuffle_epi8( 
   __m128i a,
   __m128i mask
);

[in] a

A 128-bit parameter that contains sixteen 8-bit integers.

[in] mask

A 128-bit byte mask.

The return value can be expressed by the following equations:

r0 = (mask0 & 0x80) ? 0 : SELECT(a, mask0 & 0x0f)

r1 = (mask1 & 0x80) ? 0 : SELECT(a, mask1 & 0x0f)

...

r15 = (mask15 & 0x80) ? 0 : SELECT(a, mask15 & 0x0f)

Intrinsic

Architecture

_mm_shuffle_epi8

x86, x64

Header file <tmmintrin.h>

r0-r15 and mask0-mask15 are the sequentially ordered 8-bit components of return value r and parameter mask. r0 and mask0 are the least significant 8 bits.

SELECT(a, n) extracts the nth 8-bit parameter from a. The 0th 8-bit parameter is the least significant 8-bits.

mask provides the mapping of bytes from parameter a to bytes in the result. If the byte in mask has its highest bit set, the corresponding byte in the result will be set to zero.

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

#include <stdio.h>
#include <tmmintrin.h>

int main ()
{
    __m128i a, mask;

    a.m128i_i8[0] = 1;
    a.m128i_i8[1] = 2;
    a.m128i_i8[2] = 4;
    a.m128i_i8[3] = 8;
    a.m128i_i8[4] = 16;
    a.m128i_i8[5] = 32;
    a.m128i_i8[6] = 64;
    a.m128i_i8[7] = 127;
    a.m128i_i8[8] = -2;
    a.m128i_i8[9] = -4;
    a.m128i_i8[10] = -8;
    a.m128i_i8[11] = -16;
    a.m128i_i8[12] = -32;
    a.m128i_i8[13] = -64;
    a.m128i_i8[14] = -128;
    a.m128i_i8[15] = -1;

    mask.m128i_u8[0] = 0x8F;
    mask.m128i_u8[1] = 0x0E;
    mask.m128i_u8[2] = 0x8D;
    mask.m128i_u8[3] = 0x0C;
    mask.m128i_u8[4] = 0x8B;
    mask.m128i_u8[5] = 0x0A;
    mask.m128i_u8[6] = 0x89;
    mask.m128i_u8[7] = 0x08;
    mask.m128i_u8[8] = 0x87;
    mask.m128i_u8[9] = 0x06;
    mask.m128i_u8[10] = 0x85;
    mask.m128i_u8[11] = 0x04;
    mask.m128i_u8[12] = 0x83;
    mask.m128i_u8[13] = 0x02;
    mask.m128i_u8[14] = 0x81;
    mask.m128i_u8[15] = 0x00;

    __m128i res = _mm_shuffle_epi8(a, mask);

    printf_s("Result res:\t%2d\t%2d\t%2d\t%2d\n\t\t%2d\t%2d\t%2d\t%2d\n",
                res.m128i_i8[0], res.m128i_i8[1], res.m128i_i8[2], 
                res.m128i_i8[3], res.m128i_i8[4], res.m128i_i8[5], 
                res.m128i_i8[6], res.m128i_i8[7]);
    printf_s("\t\t%2d\t%2d\t%2d\t%2d\n\t\t%2d\t%2d\t%2d\t%2d\n",
                res.m128i_i8[8],  res.m128i_i8[9], res.m128i_i8[10], 
                res.m128i_i8[11], res.m128i_i8[12], res.m128i_i8[13], 
                res.m128i_i8[14], res.m128i_i8[15]);

    return 0;
}
Result res:      0      -128     0      -32
                 0      -8       0      -2
                 0      64       0      16
                 0       4       0       1

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