[llvm] 447256f - [runtimeunroll] Fix reported DT verification error after 94d0914

[Philip Reames via llvm-commits]

Author: Philip Reames
Date: 2021-08-19T11:06:17-07:00
New Revision: 447256f22b4dc125877aed11aac875c03d0228eb

URL: https://github.com/llvm/llvm-project/commit/447256f22b4dc125877aed11aac875c03d0228eb
DIFF: https://github.com/llvm/llvm-project/commit/447256f22b4dc125877aed11aac875c03d0228eb.diff

LOG: [runtimeunroll] Fix reported DT verification error after 94d0914

In 94d0914, I added support for unrolling of multiple exit loops which have multiple exits reaching the latch.  Per reports on the review post commit, I'd missed updating the domtree for one case.  This fix addresses that ommission.

There's no new test as this is covered by existing tests with expensive verification turned on.

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 0bad348c6aa0..cd865521be43 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -285,8 +285,10 @@ static void ConnectEpilog(Loop *L, Value *ModVal, BasicBlock *NewExit,
   // Add the branch to the exit block (around the unrolling loop)
   B.CreateCondBr(BrLoopExit, EpilogPreHeader, Exit);
   InsertPt->eraseFromParent();
-  if (DT)
-    DT->changeImmediateDominator(Exit, NewExit);
+  if (DT) {
+    auto *NewDom = DT->findNearestCommonDominator(Exit, NewExit);
+    DT->changeImmediateDominator(Exit, NewDom);
+  }
 
   // Split the main loop exit to maintain canonicalization guarantees.
   SmallVector<BasicBlock*, 4> NewExitPreds{Latch};