[llvm] df4e0be - [NFC][ConstantFold] Check getAggregateElement before getSplatValue call

[Fangrui Song via llvm-commits]

Author: Senran Zhang
Date: 2021-08-03T21:52:14-07:00
New Revision: df4e0beaeb0cba052e51094ff8d9447bea11fe62

URL: https://github.com/llvm/llvm-project/commit/df4e0beaeb0cba052e51094ff8d9447bea11fe62
DIFF: https://github.com/llvm/llvm-project/commit/df4e0beaeb0cba052e51094ff8d9447bea11fe62.diff

LOG: [NFC][ConstantFold] Check getAggregateElement before getSplatValue call

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.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D107252

Added: 
    

Modified: 
    llvm/lib/IR/ConstantFold.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index e1e28d1230b0e..173117185f2af 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -667,13 +667,16 @@ Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
     }
   }
 
+  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,