[llvm] 6027e05 - [SimplifyCFG] Teach SimplifyEqualityComparisonWithOnlyPredecessor() to preserve DomTree, part 1

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2020-12-30T00:48:10+03:00
New Revision: 6027e05dbfc59a780bf6fc42d5a4f80a59878be1

URL: https://github.com/llvm/llvm-project/commit/6027e05dbfc59a780bf6fc42d5a4f80a59878be1
DIFF: https://github.com/llvm/llvm-project/commit/6027e05dbfc59a780bf6fc42d5a4f80a59878be1.diff

LOG: [SimplifyCFG] Teach SimplifyEqualityComparisonWithOnlyPredecessor() to preserve DomTree, part 1

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/test/Transforms/SimplifyCFG/2005-06-16-PHICrash.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 7d5f6daba7b2..7b08b95356fb 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -910,13 +910,18 @@ bool SimplifyCFGOpt::SimplifyEqualityComparisonWithOnlyPredecessor(
       (void)NI;
 
       // Remove PHI node entries for the dead edge.
-      ThisCases[0].Dest->removePredecessor(TI->getParent());
+      ThisCases[0].Dest->removePredecessor(PredDef);
 
       LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
                         << "Through successor TI: " << *TI << "Leaving: " << *NI
                         << "\n");
 
       EraseTerminatorAndDCECond(TI);
+
+      if (DTU)
+        DTU->applyUpdatesPermissive(
+            {{DominatorTree::Delete, PredDef, ThisCases[0].Dest}});
+
       return true;
     }
 

diff  --git a/llvm/test/Transforms/SimplifyCFG/2005-06-16-PHICrash.ll b/llvm/test/Transforms/SimplifyCFG/2005-06-16-PHICrash.ll
index 8fd1fae34503..848aec7f6ad0 100644
--- a/llvm/test/Transforms/SimplifyCFG/2005-06-16-PHICrash.ll
+++ b/llvm/test/Transforms/SimplifyCFG/2005-06-16-PHICrash.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -simplifycfg -disable-output
+; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -disable-output
 ; PR584
 @g_38098584 = external global i32		; <i32*> [#uses=1]
 @g_60187400 = external global i32		; <i32*> [#uses=1]