[llvm] [CodeGen] Introduce MI flag for Live Range split instructions (PR #117543)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

> Quote reply

> My point is why do you have to distinguish them to begin with? Can't you apply your "push down" transformation on all the COPYs that you can?
For AMDGPU the bb prolog instructions are the RA inserted spills and LR split copies. Any other instruction included as part of BBProlog would result in wrong insertion point leading to buggy CodeGen. PHI elimination pass, for instance, uses the same hook to identify the insertion point while inserting copies at the predecessor blocks. Any COPY at a block begin that was part of regular CodeGen would then be included in the prolog leading to incorrect insertion points.


https://github.com/llvm/llvm-project/pull/117543