[SLP] NFC. Set NumOperands directly if VL[0] is IntrinsicInst. (#111103)

Author: HanKuanChen

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -2312,10 +2312,10 @@ class BoUpSLP {
       assert((empty() || VL.size() == getNumLanes()) &&
              "Expected same number of lanes");
       assert(isa<Instruction>(VL[0]) && "Expected instruction");
-      unsigned NumOperands = cast<Instruction>(VL[0])->getNumOperands();
       constexpr unsigned IntrinsicNumOperands = 2;
-      if (isa<IntrinsicInst>(VL[0]))
-        NumOperands = IntrinsicNumOperands;
+      unsigned NumOperands = isa<IntrinsicInst>(VL[0])
+                                 ? IntrinsicNumOperands
+                                 : cast<Instruction>(VL[0])->getNumOperands();
       OpsVec.resize(NumOperands);
       unsigned NumLanes = VL.size();
       for (unsigned OpIdx = 0; OpIdx != NumOperands; ++OpIdx) {