[CIR] Hook the first AST node into CIR: FunctionDecl

- Add the attribute that wraps the AST node and a class helper.
- Do proper includes.
- Optionally attachable to cir.func
- Add generic verifier.

Next we should teach codegen to pass those in.

Author: bcardosolopes

clang/include/clang/CIR/Dialect/IR/CIRAttrs.h

@@ -23,6 +23,10 @@
 // CIR Dialect Attrs
 //===----------------------------------------------------------------------===//
 
+namespace clang {
+class FunctionDecl;
+}
+
 #define GET_ATTRDEF_CLASSES
 #include "clang/CIR/Dialect/IR/CIROpsAttributes.h.inc"
 

clang/include/clang/CIR/Dialect/IR/CIRAttrs.td

@@ -27,6 +27,10 @@ class CIR_Attr<string name, string attrMnemonic, list<Trait> traits = []>
   let mnemonic = attrMnemonic;
 }
 
+//===----------------------------------------------------------------------===//
+// NullAttr
+//===----------------------------------------------------------------------===//
+
 def NullAttr : CIR_Attr<"Null", "null", [TypedAttrInterface]> {
   let summary = "A simple attr to represent nullptr";
   let description = [{
@@ -38,6 +42,10 @@ def NullAttr : CIR_Attr<"Null", "null", [TypedAttrInterface]> {
   let assemblyFormat = [{}];
 }
 
+//===----------------------------------------------------------------------===//
+// CstArrayAttr
+//===----------------------------------------------------------------------===//
+
 def CstArrayAttr : CIR_Attr<"CstArray", "cst_array", [TypedAttrInterface]> {
   let summary = "A constant array from ArrayAttr or StringRefAttr";
   let description = [{
@@ -71,4 +79,31 @@ def CstArrayAttr : CIR_Attr<"CstArray", "cst_array", [TypedAttrInterface]> {
   let genVerifyDecl = 1;
 }
 
+//===----------------------------------------------------------------------===//
+// AST Wrappers
+//===----------------------------------------------------------------------===//
+
+class ASTDecl<string name, list<Trait> traits = []>
+  : CIR_Attr<!strconcat("AST", name), "ast", traits> {
+  string clang_name = !strconcat("clang::", name);
+
+  let summary = !strconcat("Wraps a ", clang_name, " AST node.");
+  let description = [{
+    Operations optionally refer to this node, they could be available depending
+    on the CIR lowering stage. Whether it's attached to the appropriated
+    CIR operation is delegated to the operation verifier.
+
+    This always implies a non-null AST reference (verified).
+  }];
+  let parameters = (ins !strconcat(clang_name, " *"):$astDecl);
+
+  // Printing and parsing available in CIRDialect.cpp
+  let hasCustomAssemblyFormat = 1;
+
+  // Enable verifier.
+  let genVerifyDecl = 1;
+}
+
+def ASTFunctionDeclAttr : ASTDecl<"FunctionDecl">;
+
 #endif // MLIR_CIR_DIALECT_CIR_ATTRS

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -1149,7 +1149,8 @@ def FuncOp : CIR_Op<"func", [
                                          "GlobalLinkageKind::ExternalLinkage">:$linkage,
                        OptionalAttr<StrAttr>:$sym_visibility,
                        OptionalAttr<DictArrayAttr>:$arg_attrs,
-                       OptionalAttr<DictArrayAttr>:$res_attrs);
+                       OptionalAttr<DictArrayAttr>:$res_attrs,
+                       OptionalAttr<ASTFunctionDeclAttr>:$ast);
   let regions = (region AnyRegion:$body);
   let skipDefaultBuilders = 1;
 

clang/lib/CIR/Dialect/IR/CIRAttrs.cpp

@@ -23,6 +23,9 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/TypeSwitch.h"
 
+// ClangIR holds back AST references when available.
+#include "clang/AST/Decl.h"
+
 #define GET_ATTRDEF_CLASSES
 #include "clang/CIR/Dialect/IR/CIROpsAttributes.cpp.inc"
 

clang/lib/CIR/Dialect/IR/CIRDialect.cpp

@@ -1420,6 +1420,27 @@ void CstArrayAttr::print(::mlir::AsmPrinter &printer) const {
   printer << ">";
 }
 
+::mlir::Attribute ASTFunctionDeclAttr::parse(::mlir::AsmParser &parser,
+                                             ::mlir::Type type) {
+  // We cannot really parse anything AST related at this point
+  // since we have no serialization/JSON story.
+  return mlir::Attribute();
+}
+
+void ASTFunctionDeclAttr::print(::mlir::AsmPrinter &printer) const {
+  // Nothing to print besides the mnemonics.
+}
+
+LogicalResult ASTFunctionDeclAttr::verify(
+    ::llvm::function_ref<::mlir::InFlightDiagnostic()> emitError,
+    ::clang::FunctionDecl *decl) {
+  if (!decl) {
+    emitError() << "expected non-null AST declaration";
+    return failure();
+  }
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // TableGen'd op method definitions
 //===----------------------------------------------------------------------===//