This allows targets to know exactly which operands are contributing to
the dependency, which is required for targets with per-operand
Required, at least, for our downstream target. I added some seemingly-relevant people from AMDGPU and Hexagon to see if they agree with the idea.
Also, I was tempted to change AMDGPU's and Hexagon's use of Src & Dst to Def & Use, as are used in the base method. The discrepancy could be a little confusing.