[llvm] 3fac056 - [VPlan] Reset trip count when replacing ExpandSCEV recipe.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2024-02-28T16:31:49Z
New Revision: 3fac0562f8bdf193f039945eb40c51a5e6c24de1

URL: https://github.com/llvm/llvm-project/commit/3fac0562f8bdf193f039945eb40c51a5e6c24de1
DIFF: https://github.com/llvm/llvm-project/commit/3fac0562f8bdf193f039945eb40c51a5e6c24de1.diff

LOG: [VPlan] Reset trip count when replacing ExpandSCEV recipe.

Otherwise accessing the trip count may accesses freed memory.

Fixes https://lab.llvm.org/buildbot/#/builders/74/builds/26239 and
others.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/lib/Transforms/Vectorize/VPlan.h

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 6b16923213c86e..ea77b6018c0d15 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -10093,6 +10093,8 @@ bool LoopVectorizePass::processLoop(Loop *L) {
           auto *ExpandedVal = BestEpiPlan.getVPValueOrAddLiveIn(
               ExpandedSCEVs.find(ExpandR->getSCEV())->second);
           ExpandR->replaceAllUsesWith(ExpandedVal);
+          if (BestEpiPlan.getTripCount() == ExpandR)
+            BestEpiPlan.resetTripCount(ExpandedVal);
           ExpandR->eraseFromParent();
         }
 

diff  --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 47cebecdb27083..16c09a83e777dd 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -2931,6 +2931,14 @@ class VPlan {
     return TripCount;
   }
 
+  /// Resets the trip count for the VPlan. The caller must make sure all uses of
+  /// the original trip count have been replaced.
+  void resetTripCount(VPValue *NewTripCount) {
+    assert(TripCount && NewTripCount && TripCount->getNumUsers() == 0 &&
+           "TripCount always must be set");
+    TripCount = NewTripCount;
+  }
+
   /// The backedge taken count of the original loop.
   VPValue *getOrCreateBackedgeTakenCount() {
     if (!BackedgeTakenCount)