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

[Tobias Grosser via Phabricator via llvm-commits]

grosser added a comment.

Hi Daniel, hi Eli,

thanks for your comments. I agree with Eli that the complexity of the approach in this patch is indeed concerning. Not saying this is the perfect solution. ;-)

@dberlin : Also thanks for your comments. I will reply in the thread.

I came up with another example that illustrates how the flattened tree "breaks" region-info, in some way.

Here one more example:

Inorder PostDominator Tree:
===========================

  [1]  <<exit node>> {0,29}
    [2] %bb24 {1,2}
    [2] %bb3 {3,10}
      [3] %bb22 {4,7}
        [4] %bb21 {5,6}
      [3] %bb {8,9}
    [2] %bb5 {11,18}
      [3] %bb19 {12,15}
        [4] %bb18 {13,14}
      [3] %bb4 {16,17}
    [2] %bb7 {19,24}
      [3] %bb16 {20,21}
      [3] %bb6 {22,23}
    [2] %bb8 {25,26}
    [2] %infloop {27,28}

F3142420: daniel.png <https://reviews.llvm.org/F3142420>

Connect in tree
===============

Inorder PostDominator Tree:

  [1]  <<exit node>> {0,29}
    [2] %bb24 {1,28}
      [3] %bb3 {2,27}
        [4] %bb22 {3,24}
          [5] %bb21 {4,23}
            [6] %bb5 {5,22}
              [7] %bb19 {6,19}
                [8] %bb18 {7,18}
                  [9] %bb7 {8,17}
                    [10] %bb16 {9,14}
                      [11] %bb8 {10,13}
                        [12] %infloop {11,12}
                    [10] %bb6 {15,16}
              [7] %bb4 {20,21}
        [4] %bb {25,26}

F3142422: grosser.png <https://reviews.llvm.org/F3142422>


https://reviews.llvm.org/D30890