[clang] [llvm] [Frontend] Add leaf constructs and association to OpenMP/ACC directives (PR #83625)

[Krzysztof Parzyszek via cfe-commits]

================
@@ -435,6 +450,217 @@ static void GenerateIsAllowedClause(const DirectiveLanguage &DirLang,
   OS << "}\n"; // End of function isAllowedClauseForDirective
 }
 
+// Generate the getLeafConstructs function implementation.
+static void GenerateGetLeafConstructs(const DirectiveLanguage &DirLang,
+                                      raw_ostream &OS) {
+  auto getQualifiedName = [&](StringRef Formatted) -> std::string {
+    return (llvm::Twine("llvm::") + DirLang.getCppNamespace() +
+            "::Directive::" + DirLang.getDirectivePrefix() + Formatted)
+        .str();
+  };
+
+  // For each list of leaves, generate a static local object, then
+  // return a reference to that object for a given directive, e.g.
+  //
+  //   static ListTy leafConstructs_A_B = { A, B };
+  //   static ListTy leafConstructs_C_D_E = { C, D, E };
+  //   switch (Dir) {
+  //     case A_B:
+  //       return leafConstructs_A_B;
+  //     case C_D_E:
+  //       return leafConstructs_C_D_E;
+  //   }
+
+  // Map from a record that defines a directive to the name of the
+  // local object with the list of its leaves.
+  DenseMap<Record *, std::string> ListNames;
+
+  std::string DirectiveTypeName =
+      std::string("llvm::") + DirLang.getCppNamespace().str() + "::Directive";
+
+  OS << '\n';
+
+  // ArrayRef<...> llvm::<ns>::GetLeafConstructs(llvm::<ns>::Directive Dir)
+  OS << "llvm::ArrayRef<" << DirectiveTypeName
+     << "> llvm::" << DirLang.getCppNamespace() << "::getLeafConstructs("
+     << DirectiveTypeName << " Dir) ";
+  OS << "{\n";
+
+  // Generate the locals.
+  for (Record *R : DirLang.getDirectives()) {
+    Directive Dir{R};
+
+    std::vector<Record *> LeafConstructs = Dir.getLeafConstructs();
+    if (LeafConstructs.empty())
+      continue;
+
+    std::string ListName = "leafConstructs_" + Dir.getFormattedName();
+    OS << "  static const " << DirectiveTypeName << ' ' << ListName
+       << "[] = {\n";
+    for (Record *L : LeafConstructs) {
+      Directive LeafDir{L};
+      OS << "    " << getQualifiedName(LeafDir.getFormattedName()) << ",\n";
+    }
+    OS << "  };\n";
----------------
kparzysz wrote:

Yes,
```
static const llvm::omp::Directive[] = {...};
```

https://github.com/llvm/llvm-project/pull/83625