[X86] combineLoad - pull out repeated cast<MemSDNode> calls. NFC.

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -49959,18 +49959,17 @@ static SDValue combineLoad(SDNode *N, SelectionDAG &DAG,
     SDValue Ptr = Ld->getBasePtr();
     SDValue Chain = Ld->getChain();
     for (SDNode *User : Chain->uses()) {
-      if (User != N &&
+      auto *UserLd = dyn_cast<MemSDNode>(User);
+      if (User != N && UserLd &&
           (User->getOpcode() == X86ISD::SUBV_BROADCAST_LOAD ||
            User->getOpcode() == X86ISD::VBROADCAST_LOAD ||
            ISD::isNormalLoad(User)) &&
-          cast<MemSDNode>(User)->getChain() == Chain &&
-          !User->hasAnyUseOfValue(1) &&
+          UserLd->getChain() == Chain && !User->hasAnyUseOfValue(1) &&
           User->getValueSizeInBits(0).getFixedValue() >
               RegVT.getFixedSizeInBits()) {
         if (User->getOpcode() == X86ISD::SUBV_BROADCAST_LOAD &&
-            cast<MemSDNode>(User)->getBasePtr() == Ptr &&
-            cast<MemSDNode>(User)->getMemoryVT().getSizeInBits() ==
-                MemVT.getSizeInBits()) {
+            UserLd->getBasePtr() == Ptr &&
+            UserLd->getMemoryVT().getSizeInBits() == MemVT.getSizeInBits()) {
           SDValue Extract = extractSubVector(SDValue(User, 0), 0, DAG, SDLoc(N),
                                              RegVT.getSizeInBits());
           Extract = DAG.getBitcast(RegVT, Extract);
@@ -49989,7 +49988,7 @@ static SDValue combineLoad(SDNode *N, SelectionDAG &DAG,
         // See if we are loading a constant that matches in the lower
         // bits of a longer constant (but from a different constant pool ptr).
         EVT UserVT = User->getValueType(0);
-        SDValue UserPtr = cast<MemSDNode>(User)->getBasePtr();
+        SDValue UserPtr = UserLd->getBasePtr();
         const Constant *LdC = getTargetConstantFromBasePtr(Ptr);
         const Constant *UserC = getTargetConstantFromBasePtr(UserPtr);
         if (LdC && UserC && UserPtr != Ptr) {