This is an archive of the discontinued LLVM Phabricator instance.

[NFCI]MemDepAnalysis] Introduce global limit on a number of instructions to be traversed during single query
AbandonedPublic

Authored by lebedev.ri on Jul 28 2020, 3:37 AM.

Details

Summary

As we have seen/established in D84108, the cut-off thresholds for Memory Dependence Analysis may need tuning.
In particular, currently they are:

  • scan up to 100 instructions per block. IMO this may be a bit low. (rL179713, changed from 500)
  • Scan up to 1000 (*sic*) blocks. That seems to be somewhat high.. (D16123)
  • There is no cumulative limit on scanned instructions, so one query can end up scanning up to 100 instructions/block * 1k blocks = 100k instructions. Just as @nikic noted in https://reviews.llvm.org/D84108#2174113, that is indeed kinda just insane.

For now, this patch simply adds said cut-off option, but the limit is presently unset.
D84609 will be lowering the limits.

Diff Detail

Event Timeline

lebedev.ri created this revision.Jul 28 2020, 3:37 AM
Harbormaster returned this revision to the author for changes because remote builds failed.Jul 28 2020, 4:50 AM
Harbormaster failed remote builds in B65988: Diff 281173!
lebedev.ri requested review of this revision.Jul 28 2020, 5:50 AM
bmahjour removed a subscriber: bmahjour.Jul 28 2020, 6:44 AM
lebedev.ri planned changes to this revision.Aug 12 2020, 2:23 PM

Not needed unless D84609 proceeds.

lebedev.ri abandoned this revision.Jan 17 2022, 2:36 PM