[llvm] c0de0a1 - [SimplifyCFG] SimplifyBranchOnICmpChain(): don't insert a DomTree edge that already exists

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-01-12T02:09:46+03:00
New Revision: c0de0a1b72c08783141c430b583e04e5107ebc0a

URL: https://github.com/llvm/llvm-project/commit/c0de0a1b72c08783141c430b583e04e5107ebc0a
DIFF: https://github.com/llvm/llvm-project/commit/c0de0a1b72c08783141c430b583e04e5107ebc0a.diff

LOG: [SimplifyCFG] SimplifyBranchOnICmpChain(): don't insert a DomTree edge that already exists

BB was already always branching to EdgeBB, there is no edge to add.

Indeed, this change does not have a test coverage change.
This failure has been exposed in an existing test coverage
by a follow-up patch that switches to lazy domtreeupdater mode,
and removes domtree verification from
SimplifyCFGOpt::simplifyOnce()/SimplifyCFGOpt::run(),
IOW it does not appear feasible to add dedicated test coverage here.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 747eb522df11..7158133f177a 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4229,7 +4229,6 @@ bool SimplifyCFGOpt::SimplifyBranchOnICmpChain(BranchInst *BI,
   // We added edges from PI to the EdgeBB.  As such, if there were any
   // PHI nodes in EdgeBB, they need entries to be added corresponding to
   // the number of edges added.
-  Updates.push_back({DominatorTree::Insert, BB, EdgeBB});
   for (BasicBlock::iterator BBI = EdgeBB->begin(); isa<PHINode>(BBI); ++BBI) {
     PHINode *PN = cast<PHINode>(BBI);
     Value *InVal = PN->getIncomingValueForBlock(BB);