[PATCH] D145599: [CodeGen] Prevent nullptr deref in genAlternativeCodeSequence

[Felipe de Azevedo Piovezan via Phabricator via llvm-commits]

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A pointer dereference was added above an assert that checks whether the
pointer is null. This commit moves the assert above the dereference and
transforms it into an llvm_unreachable to better express the intent that
certain switch cases should never be reached.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145599

Files:
  llvm/lib/CodeGen/TargetInstrInfo.cpp


Index: llvm/lib/CodeGen/TargetInstrInfo.cpp
===================================================================
--- llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -1038,15 +1038,13 @@
     Prev = MRI.getUniqueVRegDef(Root.getOperand(2).getReg());
     break;
   default:
-    break;
+    llvm_unreachable("Unknown pattern for machine combiner");
   }
 
   // Don't reassociate if Prev and Root are in different blocks.
   if (Prev->getParent() != Root.getParent())
     return;
 
-  assert(Prev && "Unknown pattern for machine combiner");
-
   reassociateOps(Root, *Prev, Pattern, InsInstrs, DelInstrs, InstIdxForVirtReg);
 }
 


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