[PATCH] D149041: [IVDescriptors] Add assert to isInductionPhi to check for invalid Phis

[Vedant Paranjape via Phabricator via llvm-commits]

vedant-amd updated this revision to Diff 516282.
vedant-amd edited the summary of this revision.
vedant-amd added a comment.

minor fix to commit message


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149041/new/

https://reviews.llvm.org/D149041

Files:
  llvm/include/llvm/Analysis/IVDescriptors.h
  llvm/lib/Analysis/IVDescriptors.cpp


Index: llvm/lib/Analysis/IVDescriptors.cpp
===================================================================
--- llvm/lib/Analysis/IVDescriptors.cpp
+++ llvm/lib/Analysis/IVDescriptors.cpp
@@ -1483,7 +1483,13 @@
         dbgs() << "LV: PHI is a recurrence with respect to an outer loop.\n");
     return false;
   }
-
+  
+  // This function assumes that InductionPhi is called only on Phi nodes 
+  // present inside loop headers. Check for the same, and throw an assert if 
+  // the current Phi is not present inside the loop header.
+  assert(Phi->getParent() == AR->getLoop()->getHeader() 
+    && "Invalid Phi node, not present in loop header");
+  
   Value *StartValue =
       Phi->getIncomingValueForBlock(AR->getLoop()->getLoopPreheader());
 
Index: llvm/include/llvm/Analysis/IVDescriptors.h
===================================================================
--- llvm/include/llvm/Analysis/IVDescriptors.h
+++ llvm/include/llvm/Analysis/IVDescriptors.h
@@ -322,7 +322,9 @@
 
   /// Returns true if \p Phi is an induction in the loop \p L. If \p Phi is an
   /// induction, the induction descriptor \p D will contain the data describing
-  /// this induction. If by some other means the caller has a better SCEV
+  /// this induction. Since Induction Phis can only be present inside loop 
+  /// headers, the function will assert if it is passed a Phi whose parent is 
+  /// not the loop header. If by some other means the caller has a better SCEV
   /// expression for \p Phi than the one returned by the ScalarEvolution
   /// analysis, it can be passed through \p Expr. If the def-use chain
   /// associated with the phi includes casts (that we know we can ignore


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