[PATCH] D58349: [Dominators] Fix and optimize edge insertion of depth-based search

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added a reviewer: kuhar.
Herald added subscribers: llvm-commits, jdoerfert, kristina.
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After (x,y) is inserted, depth-based search finds all affected v that satisfies:

depth(nca(x,y))+1 < depth(v) && there exists a path P from y to v where every w on P satisfies depth(v) <= depth(w)

This reduces to a widest path problem (maximizing the weight of the
minimum vertex in the path) which can be solved by a modified version of
BFS with a bucket queue (Depth-based search as mentioned in the paper).

The algorithm visits vertices in decreasing order of bucket number.
However, the current code misused priority_queue to extract them in
increasing order. I cannot think of a failing scenario but it surely may
process vertices more than once due to the local usage of Processed.

This patch fixes this and simplifies/optimizes the code a bit.


Repository:
  rL LLVM

https://reviews.llvm.org/D58349

Files:
  include/llvm/Support/GenericDomTreeConstruction.h

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