[SelectionDAG][NFC] Clean up SDCallSiteDbgInfo accessors

[melver]

Summary

• Consistent naming: addCallSiteInfo vs. getCallSiteInfo;
• Use ternary operator to reduce verbosity;
• const'ify getters;
• Add comments;

NFCI.

llvm/include/llvm/CodeGen/SelectionDAG.h

public:
 
   /// \returns true if \p N is any kind of constant or build_vector of
   /// constants, int or float. If a vector, it may not necessarily be a splat.
   inline bool isConstantValueOfAnyType(SDValue N) const {
     return isConstantIntBuildVectorOrConstantInt(N) ||
            isConstantFPBuildVectorOrConstantFP(N);
   }
 
-  void addCallSiteInfo(const SDNode *CallNode, CallSiteInfoImpl &&CallInfo) {
-    SDCallSiteDbgInfo[CallNode].CSInfo = std::move(CallInfo);
+  /// Set CallSiteInfo to be associated with Node.
+  void addCallSiteInfo(const SDNode *Node, CallSiteInfoImpl &&CallInfo) {
+    SDCallSiteDbgInfo[Node].CSInfo = std::move(CallInfo);
   }
-
-  CallSiteInfo getSDCallSiteInfo(const SDNode *CallNode) {
-    auto I = SDCallSiteDbgInfo.find(CallNode);
-    if (I != SDCallSiteDbgInfo.end())
-      return std::move(I->second).CSInfo;
-    return CallSiteInfo();
+  /// Return CallSiteInfo associated with Node, or a default if none exists.
+  CallSiteInfo getCallSiteInfo(const SDNode *Node) {
+    auto I = SDCallSiteDbgInfo.find(Node);
+    return I != SDCallSiteDbgInfo.end() ? std::move(I->second).CSInfo
+                                        : CallSiteInfo();
   }
-
+  /// Set HeapAllocSite to be associated with Node.
   void addHeapAllocSite(const SDNode *Node, MDNode *MD) {
     SDCallSiteDbgInfo[Node].HeapAllocSite = MD;
   }
-
-  /// Return the HeapAllocSite type associated with the SDNode, if it exists.
-  MDNode *getHeapAllocSite(const SDNode *Node) {
-    auto It = SDCallSiteDbgInfo.find(Node);
-    if (It == SDCallSiteDbgInfo.end())
-      return nullptr;
-    return It->second.HeapAllocSite;
+  /// Return HeapAllocSite associated with Node, or nullptr if none exists.
+  MDNode *getHeapAllocSite(const SDNode *Node) const {
+    auto I = SDCallSiteDbgInfo.find(Node);
+    return I != SDCallSiteDbgInfo.end() ? I->second.HeapAllocSite : nullptr;
   }
-
+  /// Set NoMergeSiteInfo to be associated with Node if NoMerge is true.
   void addNoMergeSiteInfo(const SDNode *Node, bool NoMerge) {
     if (NoMerge)
       SDCallSiteDbgInfo[Node].NoMerge = NoMerge;
   }
-
-  bool getNoMergeSiteInfo(const SDNode *Node) {
+  /// Return NoMerge info associated with Node.
+  bool getNoMergeSiteInfo(const SDNode *Node) const {
     auto I = SDCallSiteDbgInfo.find(Node);
-    if (I == SDCallSiteDbgInfo.end())
-      return false;
-    return I->second.NoMerge;
+    return I != SDCallSiteDbgInfo.end() ? I->second.NoMerge : false;
   }
 
   /// Return the current function's default denormal handling kind for the given
   /// floating point type.
   DenormalMode getDenormalMode(EVT VT) const {
     return MF->getDenormalMode(EVTToAPFloatSemantics(VT));
   }
 

llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

if (Before == BB->end()) {
       MI = &Emitter.getBlock()->instr_front();
     } else {
       // Return first instruction after the pre-existing instructions.
       MI = &*std::next(Before);
     }
 
     if (MI->isCandidateForCallSiteEntry() &&
         DAG->getTarget().Options.EmitCallSiteInfo)
-      MF.addCallArgsForwardingRegs(MI, DAG->getSDCallSiteInfo(Node));
+      MF.addCallArgsForwardingRegs(MI, DAG->getCallSiteInfo(Node));
 
     if (DAG->getNoMergeSiteInfo(Node)) {
       MI->setFlag(MachineInstr::MIFlag::NoMerge);
     }
 
     return MI;
   };