[llvm] [DebugInfo][RemoveDIs] Interpret DPValue objects in SelectionDAG (PR #72253)

[Orlando Cazalet-Hyams via llvm-commits]

================
@@ -106,54 +106,44 @@ class SelectionDAGBuilder {
 
   /// Helper type for DanglingDebugInfoMap.
   class DanglingDebugInfo {
-    using DbgValTy = const DbgValueInst *;
-    using VarLocTy = const VarLocInfo *;
-    PointerUnion<DbgValTy, VarLocTy> Info;
     unsigned SDNodeOrder = 0;
 
   public:
+    DILocalVariable *Variable;
+    DIExpression *Expression;
+    DebugLoc dl;
     DanglingDebugInfo() = default;
-    DanglingDebugInfo(const DbgValueInst *DI, unsigned SDNO)
-        : Info(DI), SDNodeOrder(SDNO) {}
-    DanglingDebugInfo(const VarLocInfo *VarLoc, unsigned SDNO)
-        : Info(VarLoc), SDNodeOrder(SDNO) {}
-
-    DILocalVariable *getVariable(const FunctionVarLocs *Locs) const {
-      if (isa<VarLocTy>(Info))
-        return Locs->getDILocalVariable(cast<VarLocTy>(Info)->VariableID);
-      return cast<DbgValTy>(Info)->getVariable();
+    DanglingDebugInfo(DILocalVariable *Var, DIExpression *Expr, DebugLoc DL, unsigned SDNO)
+        : SDNodeOrder(SDNO), Variable(Var), Expression(Expr), dl(std::move(DL)) {}
+
+    DILocalVariable *getVariable() const {
+      return Variable;
     }
     DIExpression *getExpression() const {
-      if (isa<VarLocTy>(Info))
-        return cast<VarLocTy>(Info)->Expr;
-      return cast<DbgValTy>(Info)->getExpression();
-    }
-    Value *getVariableLocationOp(unsigned Idx) const {
-      assert(Idx == 0 && "Dangling variadic debug values not supported yet");
-      if (isa<VarLocTy>(Info))
-        return cast<VarLocTy>(Info)->Values.getVariableLocationOp(Idx);
-      return cast<DbgValTy>(Info)->getVariableLocationOp(Idx);
+      return Expression;
     }
     DebugLoc getDebugLoc() const {
-      if (isa<VarLocTy>(Info))
-        return cast<VarLocTy>(Info)->DL;
-      return cast<DbgValTy>(Info)->getDebugLoc();
+      return dl;
     }
     unsigned getSDNodeOrder() const { return SDNodeOrder; }
 
     /// Helper for printing DanglingDebugInfo. This hoop-jumping is to
     /// accommodate the fact that an argument is required for getVariable.
     /// Call SelectionDAGBuilder::printDDI instead of using directly.
     struct Print {
-      Print(const DanglingDebugInfo &DDI, const FunctionVarLocs *VarLocs)
-          : DDI(DDI), VarLocs(VarLocs) {}
+      Print(const Value *V, const DanglingDebugInfo &DDI)
+          : V(V), DDI(DDI) {}
+      const Value *V;
       const DanglingDebugInfo &DDI;
-      const FunctionVarLocs *VarLocs;
       friend raw_ostream &operator<<(raw_ostream &OS,
                                      const DanglingDebugInfo::Print &P) {
-        OS << "DDI(var=" << *P.DDI.getVariable(P.VarLocs)
-           << ", val= " << *P.DDI.getVariableLocationOp(0)
-           << ", expr=" << *P.DDI.getExpression()
+        OS << "DDI(var=" << *P.DDI.getVariable();
----------------
OCHyams wrote:

If the parameter isn't needed anymore `getVariable(P.VarLocs)`
```
    /// Helper for printing DanglingDebugInfo. This hoop-jumping is to
    /// accommodate the fact that an argument is required for getVariable.
    /// Call SelectionDAGBuilder::printDDI instead of using directly.
```

Can we delete this blob of code?

https://github.com/llvm/llvm-project/pull/72253