Vectorisation of Load and Store requires creation, from scalar operations,
a number of different modes:
-* fixed stride (contiguous sequence with no gaps)
+* fixed stride (contiguous sequence with no gaps) aka "unit" stride
* element strided (sequential but regularly offset, with gaps)
* vector indexed (vector of base addresses and vector of offsets)
* fail-first on the same (where it makes sense to do so)
this section covers assembly notation for the immediate and indexed LD/ST.
the summary is that in immediate mode for LD it is not clear that if the
destination register is Vectorised `RT.v` but the source `imm(RA)` is scalar
-the memory being read is *still a vector load*.
+the memory being read is *still a vector load*, known as "unit or element strides".
This anomaly is made clear with the following notation: