_mm_rot_epi8

Artigo
07/22/2011

[Note: This document describes a pre-release version of Visual Studio 2010 SP1 and may be revised in any later version.]

Visual Studio 2010 SP1 is required.

Microsoft Specific

Generates the XOP instruction vprotb to rotate each of the bytes in its first source by an amount specified in the second.

__m128i _mm_rot_epi8 (
   __m128i src,
   __m128i counts
);

Parameters

[in] src
A 128-bit parameter that contains sixteen 8-bit unsigned integers.
[in] counts
A 128-bit parameter that contains sixteen 8-bit signed integers.

Return value

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

r[i] := (counts[i] > 0) ? rotate_left(src[i], counts[i]) : 
                          rotate_right(src[i], -counts[i]);

Requirements

Intrinsic	Architecture
_mm_rot_epi8	XOP

Header file <intrin.h>

Remarks

Each 8-bit unsigned integer value in src is rotated by the number of bits specified in the corresponding value in counts, and the 8-bit unsigned integer result is stored as the corresponding value in the destination. If the value in counts is positive, the rotation is to the left (toward the most significant bit); otherwise, it is to the right.

The vprotb 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.

Example

#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 << 4) | (15 - i);
        b.m128i_i8[i] = i - 8;
    }
    printf_s("data:       ");
    for (i = 0; i < 16; i++) printf_s(" %02x", a.m128i_u8[i]);
    printf_s("\nrotated by  ");
    for (i = 0; i < 16; i++) printf_s(" %2d", b.m128i_i8[i]);
    d = _mm_rot_epi8(a, b);
    printf_s("\ngives       ");
    for (i = 0; i < 16; i++) printf_s(" %02x", d.m128i_u8[i]);
    printf_s("\n");
}

data:        0f 1e 2d 3c 4b 5a 69 78 87 96 a5 b4 c3 d2 e1 f0
rotated by   -8 -7 -6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7
gives        0f 3c b4 e1 b4 4b 5a 3c 87 2d 96 a5 3c 5a 78 78

Change History

Date	History	Reason
March 2011	Added this content.	SP1 feature change.

March 2011

Added this content.

SP1 feature change.

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