From: Fangrui Song <maskray@google.com>
Date: Wed, 20 Feb 2019 02:35:24 +0000 (+0000)
Subject: [Dominators] Delete UpdateLevelsAfterInsertion in edge insertion of depth-based searc... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f3778debe6659ff82bbf5414239858d998a9f3cc;p=llvm

[Dominators] Delete UpdateLevelsAfterInsertion in edge insertion of depth-based search for release builds

Summary:
After insertion of (From, To), v is affected iff
depth(NCD)+1 < depth(v) && path P from To to v exists where every w on P s.t. depth(v) <= depth(w)

All affected vertices change their idom to NCD.

If a vertex u has changed its depth, it must be a descendant of an
affected vertex v. Its depth must have been updated by UpdateLevel()
called by setIDom() of the first affected ancestor.

So UpdateLevelsAfterInsertion and its bookkeeping variable VisitedNotAffectedQueue are redundant.
Run them only in debug builds as a sanity check.

Reviewers: kuhar

Reviewed By: kuhar

Subscribers: kristina, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58369

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354429 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Support/GenericDomTreeConstruction.h b/include/llvm/Support/GenericDomTreeConstruction.h
index 1a5712408a7..7ba907e94e2 100644
--- a/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/include/llvm/Support/GenericDomTreeConstruction.h
@@ -632,7 +632,9 @@ struct SemiNCAInfo {
         Bucket;
     SmallDenseSet<TreeNodePtr, 8> Visited;
     SmallVector<TreeNodePtr, 8> Affected;
-    SmallVector<TreeNodePtr, 8> VisitedNotAffectedQueue;
+#ifndef NDEBUG
+    SmallVector<TreeNodePtr, 8> VisitedUnaffected;
+#endif
   };
 
   static void InsertEdge(DomTreeT &DT, const BatchUpdatePtr BUI,
@@ -800,8 +802,10 @@ struct SemiNCAInfo {
             // vertices. Store it in UnaffectedOnCurrentLevel.
             LLVM_DEBUG(dbgs() << "\t\tMarking visited not affected "
                               << BlockNamePrinter(Succ) << "\n");
-            II.VisitedNotAffectedQueue.push_back(SuccTN);
             UnaffectedOnCurrentLevel.push_back(SuccTN);
+#ifndef NDEBUG
+            II.VisitedUnaffected.push_back(SuccTN);
+#endif
           } else {
             // The condition is satisfied (Succ is affected). Add Succ to the
             // bucket queue.
@@ -833,20 +837,13 @@ struct SemiNCAInfo {
       TN->setIDom(NCD);
     }
 
-    UpdateLevelsAfterInsertion(II);
-    if (IsPostDom) UpdateRootsAfterUpdate(DT, BUI);
-  }
-
-  static void UpdateLevelsAfterInsertion(InsertionInfo &II) {
-    LLVM_DEBUG(
-        dbgs() << "Updating levels for visited but not affected nodes\n");
+#ifndef NDEBUG
+    for (const TreeNodePtr TN : II.VisitedUnaffected)
+      assert(TN->getLevel() == TN->getIDom()->getLevel() + 1 &&
+             "TN should have been updated by an affected ancestor");
+#endif
 
-    for (const TreeNodePtr TN : II.VisitedNotAffectedQueue) {
-      LLVM_DEBUG(dbgs() << "\tlevel(" << BlockNamePrinter(TN) << ") = ("
-                        << BlockNamePrinter(TN->getIDom()) << ") "
-                        << TN->getIDom()->getLevel() << " + 1\n");
-      TN->UpdateLevel();
-    }
+    if (IsPostDom) UpdateRootsAfterUpdate(DT, BUI);
   }
 
   // Handles insertion to previously unreachable nodes.