[PATCH] D30890: Post-dom fix - connect virtual edges to last reverse-reachable BB

[Tobias Grosser via Phabricator via llvm-commits]

grosser created this revision.
Herald added a subscriber: david2050.

This change is an adapted version of Daniel's "Fix PR 24415 (at least), by
making our post-dominator tree behavior sane." patch, which ensures that
we correctly detect SESE regions that contain infinite loops.

To remain consistent we handle unreachable() basic blocks the same way as
infinite loops.

This is a proof-of-concept patch used in the discussion on how to properly
complete the post-dominator tree to include reverse unreachable nodes.


https://reviews.llvm.org/D30890

Files:
  include/llvm/ADT/GraphTraits.h
  include/llvm/Analysis/RegionInfoImpl.h
  include/llvm/IR/CFG.h
  include/llvm/Support/GenericDomTree.h
  include/llvm/Support/GenericDomTreeConstruction.h
  lib/Transforms/Scalar/ADCE.cpp
  test/Analysis/PostDominators/pr24415.ll
  test/Analysis/PostDominators/pr6047_a.ll
  test/Analysis/PostDominators/pr6047_b.ll
  test/Analysis/PostDominators/pr6047_c.ll
  test/Analysis/PostDominators/pr6047_d.ll
  test/Analysis/RegionInfo/infinite_loop.ll
  test/Analysis/RegionInfo/infinite_loop_2.ll
  test/Analysis/RegionInfo/infinite_loop_3.ll
  test/Analysis/RegionInfo/infinite_loop_4.ll
  test/Analysis/RegionInfo/infinite_loop_5_a.ll
  test/Analysis/RegionInfo/infinite_loop_5_b.ll
  test/Transforms/StructurizeCFG/branch-on-argument.ll
  test/Transforms/StructurizeCFG/no-branch-to-entry.ll

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