[all-commits] [llvm/llvm-project] 0e0889: [DA] control compile-time spent by MIV tests

[Bardia Mahjour via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0e08891ec1a63850c99cfe270ae5370150a12d29
      https://github.com/llvm/llvm-project/commit/0e08891ec1a63850c99cfe270ae5370150a12d29
  Author: Bardia Mahjour <bmahjour at ca.ibm.com>
  Date:   2021-08-05 (Thu, 05 Aug 2021)

  Changed paths:
    M llvm/lib/Analysis/DependenceAnalysis.cpp
    A llvm/test/Analysis/DependenceAnalysis/MIVMaxLevelThreshold.ll

  Log Message:
  -----------
  [DA] control compile-time spent by MIV tests

Function exploreDirections() in DependenceAnalysis implements a recursive
algorithm for refining direction vectors. This algorithm has worst-case
complexity of O(3^(n+1)) where n is the number of common loop levels.
In this patch I'm adding a threshold to control the amount of time we
spend in doing MIV tests (which most of the time end up resulting in over
pessimistic direction vectors anyway).

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D107159