[Patch]SLP vectorization on tiny fully vectorizable tree

[Yi Jiang]

Hi,

In the original slp vectorizer, we do not handle tiny tree (height less than 3) and expect that the backend could combine. However, the backend can not handle cases below due to lack of alias information; we have global alias analysis in backend but it is not enable in all back end:
{
   // we know dest does not alias to src
   dest[0] = src[0];
   dest[1] = src[1];
}

In this patch, we will enable slp vectorization on tinny fully vectorizable tree like that.  


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