JIT: Remove some fgWalkTree uses (#71767)

Convert them to GenTreeVisitor.

src/coreclr/jit/compiler.h

@@ -2702,8 +2702,6 @@ class Compiler
 
  void gtUpdateNodeOperSideEffects(GenTree* tree);
 
- void gtUpdateNodeOperSideEffectsPost(GenTree* tree);
-
  // Returns "true" iff the complexity (not formally defined, but first interpretation
  // is #of nodes in subtree) of "tree" is greater than "limit".
  // (This is somewhat redundant with the "GetCostEx()/GetCostSz()" fields, but can be used
@@ -5930,9 +5928,6 @@ class Compiler
  bool fgForwardSubBlock(BasicBlock* block);
  bool fgForwardSubStatement(Statement* statement);
 
- static fgWalkPreFn fgUpdateSideEffectsPre;
- static fgWalkPostFn fgUpdateSideEffectsPost;
-
  // The given local variable, required to be a struct variable, is being assigned via
  // a "lclField", to make it masquerade as an integral type in the ABI. Make sure that
  // the variable is not enregistered, and is therefore not promoted independently.
@@ -6468,7 +6463,7 @@ class Compiler
  int arrayLengthCount;
  };
 
- static fgWalkResult optInvertCountTreeInfo(GenTree** pTree, fgWalkData* data);
+ OptInvertCountTreeInfoType optInvertCountTreeInfo(GenTree* tree);
 
  bool optInvertWhileLoop(BasicBlock* block);
 
@@ -6486,9 +6481,19 @@ class Compiler
  bool dupCond,
  unsigned* iterCount);
 
- static fgWalkPreFn optIsVarAssgCB;
-
 protected:
+ struct isVarAssgDsc
+ {
+ GenTree* ivaSkip;
+ ALLVARSET_TP ivaMaskVal; // Set of variables assigned to. This is a set of all vars, not tracked vars.
+ unsigned ivaVar; // Variable we are interested in, or -1
+ varRefKinds ivaMaskInd; // What kind of indirect assignments are there?
+ callInterf ivaMaskCall; // What kind of calls are there?
+ bool ivaMaskIncomplete; // Variables not representable in ivaMaskVal were assigned to.
+ };
+
+ bool optIsVarAssignedWithDesc(Statement* stmt, isVarAssgDsc* dsc);
+
  bool optIsVarAssigned(BasicBlock* beg, BasicBlock* end, GenTree* skip, unsigned var);
 
  bool optIsVarAssgLoop(unsigned lnum, unsigned var);
@@ -6735,19 +6740,6 @@ class Compiler
 
  void optOptimizeCSEs();
 
- struct isVarAssgDsc
- {
- GenTree* ivaSkip;
- ALLVARSET_TP ivaMaskVal; // Set of variables assigned to. This is a set of all vars, not tracked vars.
-#ifdef DEBUG
- void* ivaSelf;
-#endif
- unsigned ivaVar; // Variable we are interested in, or -1
- varRefKinds ivaMaskInd; // What kind of indirect assignments are there?
- callInterf ivaMaskCall; // What kind of calls are there?
- bool ivaMaskIncomplete; // Variables not representable in ivaMaskVal were assigned to.
- };
-
  static callInterf optCallInterf(GenTreeCall* call);
 
 public: