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Visual Studio 2010

Visual Studio 2010 SP1 is required.

Microsoft Specific

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

__m128i _mm_rot_epi16 (
   __m128i src,
   __m128i counts

[in] src

A 128-bit parameter that contains eight 16-bit unsigned integers.

[in] counts

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

A 128-bit result r that contains eight 16-bit unsigned integers.

r[i] := (counts[2*i] > 0) ? rotate_left(src[i], counts[2*i]) : 
                            rotate_right(src[i], -counts[2*i]);





Header file <intrin.h>

Each 16-bit unsigned integer value in src is rotated by the number of bits specified by the value in the byte of counts corresponding to its low-order byte, and the 16-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 other bytes of counts are ignored.

The vprotw 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 < 8; i++) {
        a.m128i_u16[i] = (2*(i+1)) << 12 | (15 - 2*(i+1)) << 8 |
                          2*i << 4 | (15 - 2*i);
        b.m128i_i8[2*i] = 3*i - 12;
    printf_s("data:       ");
    for (i = 0; i < 8; i++) printf_s(" %04x", a.m128i_u16[i]);
    printf_s("\nrotated by  ");
    for (i = 0; i < 8; i++) printf_s(" %4d", b.m128i_i8[2*i]);
    d = _mm_rot_epi16(a, b);
    printf_s("\ngives       ");
    for (i = 0; i < 8; i++) printf_s(" %04x", d.m128i_u16[i]);
data:        2d0f 4b2d 694b 8769 a587 c3a5 e1c3 ffe1
rotated by    -12   -9   -6   -3    0    3    6    9
gives        d0f2 96a5 2da5 30ed a587 1d2e 70f8 c3ff

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