[SCEV] Follow up of D71563: addressing post commit comment. NFC.

Author: Sjoerd Meijer

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -4507,17 +4507,6 @@ static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) {
   if (!Op)
     return None;
 
-  // Recognise intrinsic loop.decrement.reg, and as this has exactly the same
-  // semantics as a Sub, return a binary sub expression.
-  if (auto *II = dyn_cast<IntrinsicInst>(V)) {
-    switch (II->getIntrinsicID()) {
-    case Intrinsic::loop_decrement_reg:
-      return BinaryOp(Instruction::Sub, II->getOperand(0), II->getOperand(1));
-    default:
-      return None;
-    }
-  }
-
   // Implementation detail: all the cleverness here should happen without
   // creating new SCEV expressions -- our caller knowns tricks to avoid creating
   // SCEV expressions when possible, and we should not break that.
@@ -4586,6 +4575,12 @@ static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) {
     break;
   }
 
+  // Recognise intrinsic loop.decrement.reg, and as this has exactly the same
+  // semantics as a Sub, return a binary sub expression.
+  if (auto *II = dyn_cast<IntrinsicInst>(V))
+    if (II->getIntrinsicID() == Intrinsic::loop_decrement_reg)
+      return BinaryOp(Instruction::Sub, II->getOperand(0), II->getOperand(1));
+
   return None;
 }