[X86][AVX512][Clang][Intrinsics][reduce] Adding missing reduce (Operators:...

[X86][AVX512][Clang][Intrinsics][reduce] Adding missing reduce (Operators: +,*,&&,||) intrinsics to Clang
 
Committed after LGTM and check-all

 
Vector-reduction arithmetic accepts vectors as inputs and produces scalars as outputs.
This class of vector operation forms the basis of many scientific computations.
In vector-reduction arithmetic, the evaluation off is independent of the order of the input elements of V.
 
Used bisection method. At each step, we partition the vector with previous
step in half, and the operation is performed on its two halves.
This takes log2(n) steps where n is the number of elements in the vector.
 
Reviwer: 1. igorb
         2. craig.topper    
Differential Revision: https://reviews.llvm.org/D25527

llvm-svn: 285054