# Addition Intrinsics

These Supplemental Streaming SIMD Extensions 3 (SSSE3) intrinsics are used for horizontal addition. The prototypes for these intrinsics are in tmmintrin.h.

To use these intrinsics, include the immintrin.h file as follows:

    #include <immintrin.h>

## _mm_hadd_epi16

extern __m128i _mm_hadd_epi16(__m128i a, __m128i b);

Adds horizontally packed signed words. Interpreting a, b, and r as arrays of 16-bit signed integers:

    for (i = 0; i < 4; i++) {
    r[i] = a[2*i] + a[2i+1];
    r[i+4] = b[2*i] + b[2*i+1];
    }

## _mm_hadd_epi32

extern __m128i _mm_hadd_epi32(__m128i a, __m128i b);

Adds horizontally packed signed doublewords. Interpreting a, b, and r as arrays of 32-bit signed integers:

    for (i = 0; i < 2; i++) {
    r[i] = a[2*i] + a[2i+1];
    r[i+2] = b[2*i] + b[2*i+1];
    }

## _mm_hadds_epi16

extern __m128i _mm_hadds_epi16(__m128i a, __m128i b);

Adds horizontally packed signed words with signed saturation. Interpreting a, b, and r as arrays of 16-bit signed integers:

    for (i = 0; i < 4; i++) {
    r[i] = signed_saturate_to_word(a[2*i] + a[2i+1]);
    r[i+4] = signed_saturate_to_word(b[2*i] + b[2*i+1]);
    }

## _mm_hadd_pi16

extern __m64 _mm_hadd_pi16(__m64 a, __m64 b);

Adds horizontally packed signed words. Interpreting a, b, and r as arrays of 16-bit signed integers:

    for (i = 0; i < 2; i++) {
    r[i] = a[2*i] + a[2i+1];
    r[i+2] = b[2*i] + b[2*i+1];
    }

## _mm_hadd_pi32

extern __m64 _mm_hadd_pi32(__m64 a, __m64 b);

Adds horizontally packed signed doublewords. Interpreting a, b, and r as arrays of 32-bit signed integers:

    r[0] = a[1] + a[0];
    r[1] = b[1] + b[0];

## _mm_hadds_pi16

extern __m64 _mm_hadds_pi16(__m64 a, __m64 b);

Adds horizontally packed signed words with signed saturation. Interpreting a, b, and r as arrays of 16-bit signed integers:

    for (i = 0; i < 2; i++) {
    r[i] = signed_saturate_to_word(a[2*i] + a[2i+1]);
    r[i+2] = signed_saturate_to_word(b[2*i] + b[2*i+1]);
    }

Parent topic: Intrinsics for Intel® Supplemental Streaming SIMD Extensions 3 (SSSE3)