constify getUnderlyingObject implementation [nfc]

llvm/include/llvm/Analysis/ValueTracking.h

@@ -370,10 +370,11 @@ constexpr unsigned MaxAnalysisRecursionDepth = 6;
   /// that the returned value has pointer type if the specified value does. If
   /// the MaxLookup value is non-zero, it limits the number of instructions to
   /// be stripped off.
-  Value *getUnderlyingObject(Value *V, unsigned MaxLookup = 6);
-  inline const Value *getUnderlyingObject(const Value *V,
-                                          unsigned MaxLookup = 6) {
-    return getUnderlyingObject(const_cast<Value *>(V), MaxLookup);
+  const Value *getUnderlyingObject(const Value *V, unsigned MaxLookup = 6);
+  inline Value *getUnderlyingObject(Value *V, unsigned MaxLookup = 6) {
+    // Force const to avoid infinite recursion.
+    const Value *VConst = V;
+    return const_cast<Value *>(getUnderlyingObject(VConst, MaxLookup));
   }
 
   /// This method is similar to getUnderlyingObject except that it can

llvm/lib/Analysis/ValueTracking.cpp

@@ -4299,18 +4299,18 @@ static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
   return true;
 }
 
-Value *llvm::getUnderlyingObject(Value *V, unsigned MaxLookup) {
+const Value *llvm::getUnderlyingObject(const Value *V, unsigned MaxLookup) {
   if (!V->getType()->isPointerTy())
     return V;
   for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
-    if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
+    if (auto *GEP = dyn_cast<GEPOperator>(V)) {
       V = GEP->getPointerOperand();
     } else if (Operator::getOpcode(V) == Instruction::BitCast ||
                Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
       V = cast<Operator>(V)->getOperand(0);
       if (!V->getType()->isPointerTy())
         return V;
-    } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
+    } else if (auto *GA = dyn_cast<GlobalAlias>(V)) {
       if (GA->isInterposable())
         return V;
       V = GA->getAliasee();