[PATCH] D107252: [NFC][ConstantFold] Check getAggregateElement before getSplatValue call

[Senran Zhang via Phabricator via llvm-commits]

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Constant::getSplatValue has O(N) time complexity in the worst case,
where N is the # of elements in a vector. So we call
Constant::getAggregateElement first and return earlier if possible to
avoid unnecessary getSplatValue calls.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107252

Files:
  llvm/lib/IR/ConstantFold.cpp


Index: llvm/lib/IR/ConstantFold.cpp
===================================================================
--- llvm/lib/IR/ConstantFold.cpp
+++ llvm/lib/IR/ConstantFold.cpp
@@ -667,13 +667,16 @@
     }
   }
 
+  if (Constant *C = Val->getAggregateElement(CIdx))
+    return C;
+
   // Lane < Splat minimum vector width => extractelt Splat(x), Lane -> x
   if (CIdx->getValue().ult(ValVTy->getElementCount().getKnownMinValue())) {
     if (Constant *SplatVal = Val->getSplatValue())
       return SplatVal;
   }
 
-  return Val->getAggregateElement(CIdx);
+  return nullptr;
 }
 
 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,


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