[all-commits] [llvm/llvm-project] 1a2513: [DAGCombine] Skip re-visiting EntryToken to avoid ...

[Ulrich Weigand via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 1a25133bcdfeb525168ed4bd7e747463e635d0a4
      https://github.com/llvm/llvm-project/commit/1a25133bcdfeb525168ed4bd7e747463e635d0a4
  Author: Ulrich Weigand <ulrich.weigand at de.ibm.com>
  Date:   2020-09-09 (Wed, 09 Sep 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

  Log Message:
  -----------
  [DAGCombine] Skip re-visiting EntryToken to avoid compile time explosion

During the main DAGCombine loop, whenever a node gets replaced, the new
node and all its users are pushed onto the worklist.  Omit this if the
new node is the EntryToken (e.g. if a store managed to get optimized
out), because re-visiting the EntryToken and its users will not uncover
any additional opportunities, but there may be a large number of such
users, potentially causing compile time explosion.

This compile time explosion showed up in particular when building the
SingleSource/UnitTests/matrix-types-spec.cpp test-suite case on any
platform without SIMD vector support.

Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D86963