[PATCH] D51664: [IR] Lazily number instructions for local dominance queries

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith added a comment.

In D51664#1877029 <https://reviews.llvm.org/D51664#1877029>, @rnk wrote:

> I still think we should do this. I think @fhahn is reimplementing DSE using MemorySSA, so presumably the DSE cases won't be an issue soon, but setting all that aside, I still think it would be nice if we could say once and for all that `Instruction::dominates(Instruction*)` is amortized `O(1)` if you haven't modified the instruction stream. Otherwise this kind of pathology will pop up again. Putting the ordering on the IR saves clients from ferrying around and maintaining OrderedInstructions / OrderedBasicBlock data structures, and that seems like a win.


I'm strongly in favour of this too.  Is there any reviewer you're specifically waiting for?  Or should the RFC be bumped to ensure there's consensus before you spend the time rebasing?


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