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

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added a comment.

> 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).



================
Comment at: lib/CodeGen/RegisterScavenging.cpp:54
-  assert(MRI->tracksLiveness() &&
-         "Cannot use register scavenger with inaccurate liveness");
-
----------------
Removing that assert seems strange.
I was thinking this is okay because it will be checked anyway when we use MachineBasicBlock::liveins(), but was this your intent?


https://reviews.llvm.org/D27562