[PATCH] D27562: CodeGen: Assert that liveness is up to date when reading block live-ins.

Mon Jan 2 05:41:32 PST 2017

MatzeB added a comment.

In https://reviews.llvm.org/D27562#627387, @qcolombet wrote:

> > Turns out not computing live-in lists when trackLivenessAfterRegAlloc() is too aggressive for todays LLVM (for example MachineLICM which is setup as part of TargetPassConfig::addOptimizedRegAlloc() requires up-to-date live-in lists.
>
> Could you elaborate on the implications?
>  I stopped reviewing the patch when you put this comment but I didn't see any change on MachineLICM for instance, so I thought something bigger was still coming, but given the ping, it seems I missed the purpose of the comment x).

That comment was just about what changed in the updated version of the patch: My previous patch was more aggressive and disabled all live-in information if tracksLivenessAfterRegAlloc() was false. Turned out that doesn't work yet, so I left that for another day/patch.

This patch now just adds an assert and fixes instance where the block live-in lists are used in situations in which they are possibly out of date.

https://reviews.llvm.org/D27562