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_mm_sha_epi8

Visual Studio 2010

Visual Studio 2010 SP1 is required.

Microsoft Specific

Generates the XOP instruction vpshab to do an arithmetic shift of each of the bytes in its first source by an amount specified in the second.

__m128i _mm_sha_epi8 (
   __m128i src,
   __m128i counts
);

[in] src

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

[in] counts

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

A 128-bit result r that contains sixteen 8-bit signed integers.

r[i] := (counts[i] >= 0) ? src[i] << counts[i]) : 
                           src[i] >> -counts[i]);

Intrinsic

Architecture

_mm_sha_epi8

XOP

Header file <intrin.h>

Each 8-bit signed integer value in src is shifted by the number of bits specified in the corresponding value in counts, and the 8-bit signed integer result is stored as the corresponding value in the destination. If the value in counts is positive, the shift is to the left (toward the most significant bit) and zeros are shifted in at the right end; otherwise, it is to the right and copies of the sign bit are shifted in at the left end. If a shift count is greater than 7 the corresponding result value is 0; if a shift count is less than -7, the result is -1 if the value in src is negative, 0 otherwise.

The vpshab instruction is part of the XOP family of instructions. Before you use this intrinsic, you must ensure that the processor supports this instruction. To determine hardware support for this instruction, call the __cpuid intrinsic with InfoType = 0x80000001 and check bit 11 of CPUInfo[2] (ECX). This bit is 1 when the instruction is supported, and 0 otherwise.

#include <stdio.h>
#include <intrin.h>
int main()
{
    __m128i a, b, d;
    int i;
    for (i = 0; i < 16; i++) {
        a.m128i_u8[i] = i | (15 - i) << 4;
        b.m128i_i8[i] = i - 8;
    }
    printf_s("data:       ");
    for (i = 0; i < 16; i++) printf_s(" %02x", a.m128i_u8[i]);
    printf_s("\nshifted by  ");
    for (i = 0; i < 16; i++) printf_s(" %2d", b.m128i_i8[i]);
    d = _mm_sha_epi8(a, b);
    printf_s("\ngives       ");
    for (i = 0; i < 16; i++) printf_s(" %02x", d.m128i_u8[i]);
    printf_s("\n");
}
data:        f0 e1 d2 c3 b4 a5 96 87 78 69 5a 4b 3c 2d 1e 0f
shifted by   -8 -7 -6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7
gives        ff ff ff fe fb f4 e5 c3 78 d2 68 58 c0 a0 80 80

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