[MLIR] Add llvm.noalias attribute to nGraph func args (#3232)
[MLIR] Add llvm.noalias attribute to nGraph func args (#3232)

Aliasing prevents vectorization and other optimizations in LLVM (dot2d,
for example). I found that LLVM dialect contemplates the possibility of
previous dialects adding llvm.noalias attribute to function arguments so
that the NoAlias attribute is generated in LLVM-IR. This should be good for
now although we should discuss how to model this in Standard dialect and co.
NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph