_mm_com_epi8

[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 vpcomb to return a bitmask generated by a byte-by-byte signed comparison of its first two sources using the condition given by the third source.

__m128i _mm_com_epi8 (
   __m128i src1,
   __m128i src2,
   int condition
);

Parameters

• [in] src1
  Packed 128-bit array of sixteen 8-bit signed integers.

• [in] src2
  Packed 128-bit array of sixteen 8-bit signed integers.

• [in] condition
  A 32-bit integer condition to be used in the comparison. Legal values are 0 through 7.

Return value

A packed 128-bit array r of sixteen eight-bit unsigned integers, each of which is either 0x00 or 0xFF. If cond is the logical operator implied by the value of condition, then

r[i] := src1[i] cond src2[i] ? 0xFF : 0x00;

Requirements

Header file <intrin.h>

Remarks

This instruction compares each byte of src1 to the corresponding byte of src2, using the comparison operator described by condition. (Each pair of bytes uses the same comparison operator.) The legal values condition are 0 through 7. By including <intrin.h> you will be able to use the following names rather than numerical values for condition:

If you prefer, you may use the following macros, which will be defined when <intrin.h> is included:

The vpcomb 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>
main()
{
  __m128i a, b, d;
    int i;
    for (i = 0; i < 16; i++) {
        a.m128i_i8[i] = ((11*i) % 31) - 16;
        b.m128i_i8[i] = ((13*i) % 31) - 16;
    }
    printf("src1:   ");
    for (i = 0; i < 16; i++) printf_s(" %3d", a.m128i_i8[i]);
    printf_s("\nsrc2:   ");
    for (i = 0; i < 16; i++) printf_s(" %3d", b.m128i_i8[i]);
    printf_s("\n<=mask: ");
    d = _mm_com_epi8(a, b, _MM_PCOMCTRL_LE);
    for (i = 0; i < 16; i++) printf_s("  %02x", d.m128i_u8[i]);
    printf_s("\n> mask: ");
    d = _mm_com_epi8(a, b, _MM_PCOMCTRL_GT);
    for (i = 0; i < 16; i++) printf_s("  %02x", d.m128i_u8[i]);
    printf("\n");
}

src1:   -16  -5   6 -14  -3   8 -12  -1  10 -10   1  12  -8   3  14  -6
src2:   -16  -3  10  -8   5 -13   0  13  -5   8 -10   3 -15  -2  11  -7
<=mask:  ff  ff  ff  ff  ff  00  ff  ff  00  ff  00  00  00  00  00  00
> mask:  00  00  00  00  00  ff  00  00  ff  00  ff  ff  ff  ff  ff  ff

See Also

Reference

_mm_com_epi16

_mm_com_epi32

_mm_com_epi64

_mm_com_epu8

XOP Intrinsics Added for Visual Studio 2010 SP1

Change History