How to fill memory fast with a `int32_t` value?

Question

Is there a function (SSEx intrinsics is OK) which will fill the memory with a specified int32_t value? For instance, when this value is equal to 0xAABBCC00 the result memory should look like:

AABBCC00AABBCC00AABBCC00AABBCC00AABBCC00
AABBCC00AABBCC00AABBCC00AABBCC00AABBCC00
AABBCC00AABBCC00AABBCC00AABBCC00AABBCC00
AABBCC00AABBCC00AABBCC00AABBCC00AABBCC00
...

I could use std::fill or simple for-loop, but it is not fast enough.

---

Resizing of a vector performed only once in the beginning of program, this is not an issue. The bottleneck is filling the memory.

Simplified code:

struct X
{
  typedef std::vector<int32_t> int_vec_t;
  int_vec_t buffer;

  X() : buffer( 5000000 ) { /* some more action */ }
  ~X() { /* some code here */ }

  // the following function is called 25 times per second
  const int_vec_t& process( int32_t background, const SOME_DATA& data );
};

const X::int_vec_t& X::process( int32_t background, const SOME_DATA& data )
{
    // the following one string takes 30% of total time of #process function
    std::fill( buffer.begin(), buffer.end(), background );

    // some processing
    // ...

    return buffer;
}

Answer 1

This is how I would do it (please excuse the Microsoft-ness of it):

VOID FillInt32(__out PLONG M, __in LONG Fill, __in ULONG Count)
{
    __m128i f;

    // Fix mis-alignment.
    if ((ULONG_PTR)M & 0xf)
    {
        switch ((ULONG_PTR)M & 0xf)
        {
            case 0x4: if (Count >= 1) { *M++ = Fill; Count--; }
            case 0x8: if (Count >= 1) { *M++ = Fill; Count--; }
            case 0xc: if (Count >= 1) { *M++ = Fill; Count--; }
        }
    }

    f.m128i_i32[0] = Fill;
    f.m128i_i32[1] = Fill;
    f.m128i_i32[2] = Fill;
    f.m128i_i32[3] = Fill;

    while (Count >= 4)
    {
        _mm_store_si128((__m128i *)M, f);
        M += 4;
        Count -= 4;
    }

    // Fill remaining LONGs.
    switch (Count & 0x3)
    {
        case 0x3: *M++ = Fill;
        case 0x2: *M++ = Fill;
        case 0x1: *M++ = Fill;
    }
}