[llvm-dev] RFC Storing BB order in llvm::Instruction for faster local dominance

[Chris Lattner via llvm-dev]

> On Sep 24, 2018, at 10:19 AM, Reid Kleckner <rnk at google.com> wrote:
> 
> To echo what Hal said, yes, it's a major change, but I think the improved complexity guarantees, simplicity, and elimination of certain classes of bugs is worth it.
> 
> I think we have consensus that we should go forward with this. Would anyone mind formally stamping it in phab? So far everyone understandably has said "makes sense to me, but I don't consider myself to have authority to stamp this.”

Hi Reid,

I have significant concerns with this patch.  I’d really appreciate it if you could address the discussion feedback here before just plowing forward with such an invasive change to the core IR.

Have you done any memory use analysis or compile time impact analysis of this change?  Have you consider the algorithm I mentioned?  I am not motivated by your rationale above, and I think it will be a huge step forward and effectively define away the problem.

-Chris