[PATCH] D91435: [AMDGPU] Split edge to make si_if dominate end_cf

[Alexander via Phabricator via llvm-commits]

alex-t marked an inline comment as done.
alex-t added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp:319-322
+    if (!DT->dominates(DefBB, BB)) {
+      // Split edge to make Def dominate Use
+      FirstInsertionPt = &*SplitEdge(DefBB, BB, DT, LI)->getFirstInsertionPt();
+    }
----------------
arsenm wrote:
> Is this the same as unconditionally calling SplitCriticalEdge?
Not really.  Any edge from the block with multiple successors to block with multiple predecessors considered critical. So, changing to unconditional call to SplitCriticalEdge involves a lot of trivial CFG patterns that do not require splitting.

For example:

        "entry"     <--  entry has 2 successors
         /        \
    "if.then"   |  <-- this edge is considered as critical
        \         /
          "end"    <-- end has 2 predecessors

At least the isCriticalEdge function in CFG.cpp : line 101 works this way


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