From 476e1b9937552b2dde191d0c3a6d3396ef9fa7e7 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Wed, 20 Feb 2019 02:35:24 +0000
Subject: [PATCH] [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

llvm-svn: 354429
---
 .../llvm/Support/GenericDomTreeConstruction.h | 27 +++++++++----------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/llvm/include/llvm/Support/GenericDomTreeConstruction.h b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
index 1a5712408a74..7ba907e94e26 100644
--- a/llvm/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/llvm/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.
@@ -833,22 +837,15 @@ struct SemiNCAInfo {
       TN->setIDom(NCD);
     }
 
-    UpdateLevelsAfterInsertion(II);
+#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
+
     if (IsPostDom) UpdateRootsAfterUpdate(DT, BUI);
   }
 
-  static void UpdateLevelsAfterInsertion(InsertionInfo &II) {
-    LLVM_DEBUG(
-        dbgs() << "Updating levels for visited but not affected nodes\n");
-
-    for (const TreeNodePtr TN : II.VisitedNotAffectedQueue) {
-      LLVM_DEBUG(dbgs() << "\tlevel(" << BlockNamePrinter(TN) << ") = ("
-                        << BlockNamePrinter(TN->getIDom()) << ") "
-                        << TN->getIDom()->getLevel() << " + 1\n");
-      TN->UpdateLevel();
-    }
-  }
-
   // Handles insertion to previously unreachable nodes.
   static void InsertUnreachable(DomTreeT &DT, const BatchUpdatePtr BUI,
                                 const TreeNodePtr From, const NodePtr To) {