[LoopIdiom] Strip dead check in processLoopMemSet (NFC) (llvm#141100)

Author: artagnon

llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

@@ -860,8 +860,6 @@ bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
     return false;
 
   const SCEV *MemsetSizeSCEV = SE->getSCEV(MSI->getLength());
-  if (!PointerStrideSCEV || !MemsetSizeSCEV)
-    return false;
 
   bool IsNegStride = false;
   const bool IsConstantSize = isa<ConstantInt>(MSI->getLength());