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Synopsis:
    #include <mmintrin.h>
    __m64 _m_pmaddwd(__m64 *m1, __m64 *m2);

Description:
    The signed 16-bit words of m1 are multiplied with the respective signed
    16-bit words of m2.  The 32-bit intermediate results are summed by pairs
    producing two 32-bit integers.


         MM[63-32] = M1[63-48] x M2[63-48]
                   + M1[47-32] x M2[47-32]
         MM[31-0]  = M1[31-16] x M2[31-16]
                   + M1[15-0]  x M2[15-0]

    In cases which overflow, the results are truncated.  These two integers
    are packed into their respective elements of the result.

Returns:
    The result of multiplying the packed signed 16-bit words of two 64-bit
    multimedia values and adding the 32-bit results pairwise is returned as
    packed double-words.

Example:
    #include <stdio.h>
    #include <mmintrin.h>

    #define AS_WORDS "%4.4x %4.4x %4.4x %4.4x"
    #define AS_DWORDS "%8.8lx %8.8lx"

    __m64   a;
    __m64   b = { 0x0000006000123456 };
    __m64   c = { 0x0000000200010020 };

    void main()
      {
        a = _m_pmaddwd( b, c );
        printf( "m1="AS_WORDS"\n"
                "m2="AS_WORDS"\n"
                "mm="AS_DWORDS"\n",
            b._16[3], b._16[2], b._16[1], b._16[0],
            c._16[3], c._16[2], c._16[1], c._16[0],
            a._32[1], a._32[0] );
      }

    produces the following:

    m1=0000 0060 0012 3456
    m2=0000 0002 0001 0020
    mm=000000c0 00068ad2

Classification:
    Intel

Systems:
    MACRO

See Also:
    _m_empty, _m_pmulhw, _m_pmullw