Armv6 introduced instructions to perform 32-bit SIMD operations. The purpose of
this pass is to do some straightforward IR pattern matching to create ACLE DSP
intrinsics, which map on these 32-bit SIMD operations. Because this is based on
simple pattern matching and it is Arm specific, we thought a separate IR pass
that runs late would be a good place to do this rather than e.g. the SLP
Currently, only the SMLAD instruction gets recognised. This does two
multiplications with 16-bit operands, and stores the result in an accumulator.
Support for more of these DSP instructions will be added later. This triggers
on a matrix-multiply kernel in a popular benchmark.