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_mm_cvtepi8_epi64

Visual Studio 2008

Microsoft Specific

Emits the Streaming SIMD Extensions 4 (SSE4) instruction pmovsxbq. This instruction performs a conversion of signed integers from 8-bit to 64-bit.

Copy 
__m128i _mm_cvtepi8_epi64( 
   __m128i a
);
[in] a

A 128-bit parameter that contains two signed 8-bit integers in the lower 16 bits.

A 128-bit result containing two 64-bit integers. These integers are sign-extended representations of the 8-bit integers that are supplied by a.

Intrinsic

Architecture

_mm_cvtepi8_epi64

x86, x64

Header file <smmintrin.h>

The result is defined as follows:

Copy 

r0 := a0
r1 := (a0 < 0) ? 0xff : 0
r2 := (a0 < 0) ? 0xff : 0
r3 := (a0 < 0) ? 0xff : 0
r4 := (a0 < 0) ? 0xff : 0
r5 := (a0 < 0) ? 0xff : 0
r6 := (a0 < 0) ? 0xff : 0
r7 := (a0 < 0) ? 0xff : 0

r8 := a1
r9 := (a1 < 0) ? 0xff : 0
r10 := (a1 < 0) ? 0xff : 0
r11 := (a1 < 0) ? 0xff : 0
r12 := (a1 < 0) ? 0xff : 0
r13 := (a1 < 0) ? 0xff : 0
r14 := (a1 < 0) ? 0xff : 0
r15 := (a1 < 0) ? 0xff : 0

r0-r15 and a0-a15 are the sequentially ordered 8-bit components of return value r and parameter a, respectively. r0 and a0 are the least significant 8 bits.

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

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#include <stdio.h>
#include <smmintrin.h>

int main ()
{
    __m128i a;

    a.m128i_i8[0] = 127;
    a.m128i_i8[1] = -128;

    __m128i res = _mm_cvtepi8_epi64(a);

    printf_s("Original lowest 8 bit integers:\n%6i,\t%6i\n\n",
        a.m128i_i8[1], a.m128i_i8[0]);

    printf_s("Resulting 64 bit integers:\n%6I64i, %6I64i\n",
        res.m128i_i64[1], res.m128i_i64[0]);

    return 0;
}
Original lowest 8 bit integers: -128, 127 Resulting 64 bit integers: -128, 127
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