[llvm-branch-commits] [llvm-branch] r292810 - Merging r292583:

[Hans Wennborg via llvm-branch-commits]

Author: hans
Date: Mon Jan 23 12:08:20 2017
New Revision: 292810

URL: http://llvm.org/viewvc/llvm-project?rev=292810&view=rev
Log:
Merging r292583:
------------------------------------------------------------------------
r292583 | dannyb | 2017-01-19 22:38:41 -0800 (Thu, 19 Jan 2017) | 4 lines

NewGVN: Fix PR 31682, an overactive assert.
Part of the assert has been left active for further debugging.
The other part has been turned into a stat for tracking for the
moment.
------------------------------------------------------------------------

Added:
    llvm/branches/release_40/test/Transforms/NewGVN/pr31682.ll
      - copied unchanged from r292583, llvm/trunk/test/Transforms/NewGVN/pr31682.ll
Modified:
    llvm/branches/release_40/   (props changed)
    llvm/branches/release_40/lib/Transforms/Scalar/NewGVN.cpp

Propchange: llvm/branches/release_40/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Mon Jan 23 12:08:20 2017
@@ -1,3 +1,3 @@
 /llvm/branches/Apple/Pertwee:110850,110961
 /llvm/branches/type-system-rewrite:133420-134817
-/llvm/trunk:155241,291858-291859,291863,291875,291966,291968,291979,292133,292242,292254-292255,292280,292641,292667,292711
+/llvm/trunk:155241,291858-291859,291863,291875,291966,291968,291979,292133,292242,292254-292255,292280,292583,292641,292667,292711

Modified: llvm/branches/release_40/lib/Transforms/Scalar/NewGVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/release_40/lib/Transforms/Scalar/NewGVN.cpp?rev=292810&r1=292809&r2=292810&view=diff
==============================================================================
--- llvm/branches/release_40/lib/Transforms/Scalar/NewGVN.cpp (original)
+++ llvm/branches/release_40/lib/Transforms/Scalar/NewGVN.cpp Mon Jan 23 12:08:20 2017
@@ -85,6 +85,8 @@ STATISTIC(NumGVNLeaderChanges, "Number o
 STATISTIC(NumGVNSortedLeaderChanges, "Number of sorted leader changes");
 STATISTIC(NumGVNAvoidedSortedLeaderChanges,
           "Number of avoided sorted leader changes");
+STATISTIC(NumGVNNotMostDominatingLeader,
+          "Number of times a member dominated it's new classes' leader");
 
 //===----------------------------------------------------------------------===//
 //                                GVN Pass
@@ -1073,17 +1075,20 @@ void NewGVN::moveValueToNewCongruenceCla
   if (I == OldClass->NextLeader.first)
     OldClass->NextLeader = {nullptr, ~0U};
 
-  // The new instruction and new class leader may either be siblings in the
-  // dominator tree, or the new class leader should dominate the new member
-  // instruction.  We simply check that the member instruction does not properly
-  // dominate the new class leader.
-  assert(
-      !isa<Instruction>(NewClass->RepLeader) || !NewClass->RepLeader ||
-      I == NewClass->RepLeader ||
-      !DT->properlyDominates(
+  // It's possible, though unlikely, for us to discover equivalences such
+  // that the current leader does not dominate the old one.
+  // This statistic tracks how often this happens.
+  // We assert on phi nodes when this happens, currently, for debugging, because
+  // we want to make sure we name phi node cycles properly.
+  if (isa<Instruction>(NewClass->RepLeader) && NewClass->RepLeader &&
+      I != NewClass->RepLeader &&
+      DT->properlyDominates(
           I->getParent(),
-          cast<Instruction>(NewClass->RepLeader)->getParent()) &&
-          "New class for instruction should not be dominated by instruction");
+          cast<Instruction>(NewClass->RepLeader)->getParent())) {
+    ++NumGVNNotMostDominatingLeader;
+    assert(!isa<PHINode>(I) &&
+           "New class for instruction should not be dominated by instruction");
+  }
 
   if (NewClass->RepLeader != I) {
     auto DFSNum = InstrDFS.lookup(I);