[clang] [NFC][Clang][OpenMP] Add helper functions/utils for finding/comparing attach base-ptrs. (PR #155625)

[Alexey Bataev via cfe-commits]

================
@@ -6848,6 +7082,45 @@ class MappableExprsHandler {
     bool HasCompleteRecord = false;
   };
 
+  /// A struct to store the attach pointer and pointee information, to be used
+  /// when emitting an attach entry.
+  struct AttachInfoTy {
+    Address AttachPtrAddr = Address::invalid();
+    Address AttachPteeAddr = Address::invalid();
+    const ValueDecl *AttachPtrDecl = nullptr;
+    const Expr *AttachMapExpr = nullptr;
+
+    bool isValid() const {
+      return AttachPtrAddr.isValid() && AttachPteeAddr.isValid();
+    }
+  };
+
+  /// Check if there's any component list where the attach pointer expression
+  /// matches the given captured variable.
+  bool hasAttachEntryForCapturedVar(const ValueDecl *VD) const {
+    for (const auto &AttachEntry : AttachPtrExprMap) {
+      if (AttachEntry.second) {
+        // Check if the attach pointer expression is a DeclRefExpr that
+        // references the captured variable
+        if (const auto *DRE = dyn_cast<DeclRefExpr>(AttachEntry.second))
+          if (DRE->getDecl() == VD)
+            return true;
+      }
+    }
+    return false;
+  }
+
+  /// Get the previously-cached attach pointer for a component list, if-any.
+  const Expr *getAttachPtrExpr(
+      OMPClauseMappableExprCommon::MappableExprComponentListRef Components)
+      const {
+    auto It = AttachPtrExprMap.find(Components);
----------------
alexey-bataev wrote:

```suggestion
    const auto It = AttachPtrExprMap.find(Components);
```

https://github.com/llvm/llvm-project/pull/155625