[llvm] 5fa241a - [SimplifyCFG] FoldValueComparisonIntoPredecessors(): fine-tune/fix DomTree preservation, take 2

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-01-03T01:45:48+03:00
New Revision: 5fa241a6571c79c1cd0c0d9e7f87e5e361e2dab4

URL: https://github.com/llvm/llvm-project/commit/5fa241a6571c79c1cd0c0d9e7f87e5e361e2dab4
DIFF: https://github.com/llvm/llvm-project/commit/5fa241a6571c79c1cd0c0d9e7f87e5e361e2dab4.diff

LOG: [SimplifyCFG] FoldValueComparisonIntoPredecessors(): fine-tune/fix DomTree preservation, take 2

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase-2.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 738e524fbfd9..d581c97f9fea 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1176,7 +1176,8 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
         // Reconstruct the new switch statement we will be building.
         if (PredDefault != BBDefault) {
           PredDefault->removePredecessor(Pred);
-          Updates.push_back({DominatorTree::Delete, Pred, PredDefault});
+          if (PredDefault != BB)
+            Updates.push_back({DominatorTree::Delete, Pred, PredDefault});
           PredDefault = BBDefault;
           NewSuccessors.push_back(BBDefault);
         }

diff  --git a/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase-2.ll b/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase-2.ll
index 79857cccfbe4..a3f7ca5e1741 100644
--- a/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase-2.ll
+++ b/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase-2.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=0 < %s | FileCheck %s
+; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s
 
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