Editing Spec.isa (section)

==== Bit slicing ====
The expression evaluator also provides syntax for picking specific bits from a value, known as "slicing". This is written as <code>value[start:end]</code> where all three parts (<code>value</code>, <code>start</code>, and <code>end</code>) can be arbitrary expressions. <code>start</code> and <code>end</code> are inclusive indices into the bits of value, with the LSB being 0 and numbering being right-to-left. To make this a bit simpler to visualize, start has to be larger than end.  For example, the slice <code>%imm[5:2]</code> applied to the value 90 (<code>0b01011010</code>) would result in 6 (<code>0b0110</code>), as shown:
<pre>
  76543210
    ||||
    vvvv
0b01011010
</pre>