[CIR] FuncType changes: respond to feedback

Incorporate llvm/clangir#1413 to simplify the
parsing/printing of `FuncType`.

Get rid of `FuncOp::verifyType` which did nothing useful.

Author: dkolsen-pgi

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

@@ -365,12 +365,6 @@ def FuncOp : CIR_Op<"func", [
        return getFunctionType().getReturnTypes();
     }
 
-    /// Hook for OpTrait::FunctionOpInterfaceTrait, called after verifying that
-    /// the 'type' attribute is present and checks if it holds a function type.
-    /// Ensures getType, getNumFuncArguments, and getNumFuncResults can be
-    /// called safely.
-    llvm::LogicalResult verifyType();
-
     //===------------------------------------------------------------------===//
     // SymbolOpInterface Methods
     //===------------------------------------------------------------------===//

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

@@ -302,10 +302,11 @@ def CIR_FuncType : CIR_Type<"Func", "func"> {
   }];
 
   let parameters = (ins ArrayRefParameter<"mlir::Type">:$inputs,
-                        "mlir::Type":$optionalReturnType, "bool":$varArg);
-  // Use a custom parser to handle the argument types and optional return
+                        OptionalParameter<"mlir::Type">:$optionalReturnType,
+                        "bool":$varArg);
+  // Use a custom parser to handle argument types with variadic elipsis.
   let assemblyFormat = [{
-    `<` custom<FuncType>($optionalReturnType, $inputs, $varArg) `>`
+    `<` custom<FuncTypeParams>($inputs, $varArg)  (`->` $optionalReturnType^)? `>`
   }];
 
   let builders = [

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

@@ -416,21 +416,6 @@ void cir::FuncOp::print(OpAsmPrinter &p) {
   }
 }
 
-// Hook for OpTrait::FunctionLike, called after verifying that the 'type'
-// attribute is present.  This can check for preconditions of the
-// getNumArguments hook not failing.
-LogicalResult cir::FuncOp::verifyType() {
-  auto type = getFunctionType();
-  if (!isa<cir::FuncType>(type))
-    return emitOpError("requires '" + getFunctionTypeAttrName().str() +
-                       "' attribute of function type");
-  if (auto rt = type.getReturnTypes();
-      !rt.empty() && mlir::isa<cir::VoidType>(rt.front()))
-    return emitOpError("The return type for a function returning void should "
-                       "be empty instead of an explicit !cir.void");
-  return success();
-}
-
 // TODO(CIR): The properties of functions that require verification haven't
 // been implemented yet.
 mlir::LogicalResult cir::FuncOp::verify() { return success(); }

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

@@ -20,12 +20,12 @@
 // CIR Custom Parser/Printer Signatures
 //===----------------------------------------------------------------------===//
 
-static mlir::ParseResult parseFuncType(mlir::AsmParser &p,
-                                       mlir::Type &optionalReturnTypes,
-                                       llvm::SmallVector<mlir::Type> &params,
-                                       bool &isVarArg);
-static void printFuncType(mlir::AsmPrinter &p, mlir::Type optionalReturnTypes,
-                          mlir::ArrayRef<mlir::Type> params, bool isVarArg);
+static mlir::ParseResult
+parseFuncTypeParams(mlir::AsmParser &p, llvm::SmallVector<mlir::Type> &params,
+                    bool &isVarArg);
+static void printFuncTypeParams(mlir::AsmPrinter &p,
+                                mlir::ArrayRef<mlir::Type> params,
+                                bool isVarArg);
 
 //===----------------------------------------------------------------------===//
 // Get autogenerated stuff
@@ -283,54 +283,31 @@ FuncType FuncType::clone(TypeRange inputs, TypeRange results) const {
   return get(llvm::to_vector(inputs), results[0], isVarArg());
 }
 
-// A special parser is needed for function returning void to handle the missing
-// type.
-static mlir::ParseResult parseFuncTypeReturn(mlir::AsmParser &p,
-                                             mlir::Type &optionalReturnType) {
-  if (succeeded(p.parseOptionalArrow())) {
-    // `->` found. It must be followed by the return type.
-    return p.parseType(optionalReturnType);
-  }
-  // Function has `void` return in C++, no return in MLIR.
-  optionalReturnType = {};
-  return success();
-}
-
-// A special pretty-printer for function returning or not a result.
-static void printFuncTypeReturn(mlir::AsmPrinter &p,
-                                mlir::Type optionalReturnType) {
-  if (optionalReturnType)
-    p << " -> " << optionalReturnType;
-}
-
+// Custom parser that parses function parameters of form `(<type>*, ...)`.
 static mlir::ParseResult
-parseFuncTypeArgs(mlir::AsmParser &p, llvm::SmallVector<mlir::Type> &params,
-                  bool &isVarArg) {
+parseFuncTypeParams(mlir::AsmParser &p, llvm::SmallVector<mlir::Type> &params,
+                    bool &isVarArg) {
   isVarArg = false;
-  if (failed(p.parseLParen()))
-    return failure();
-  if (succeeded(p.parseOptionalRParen())) {
-    // `()` empty argument list
-    return mlir::success();
-  }
-  do {
-    if (succeeded(p.parseOptionalEllipsis())) {
-      // `...`, which must be the last thing in the list.
-      isVarArg = true;
-      break;
-    } else {
-      mlir::Type argType;
-      if (failed(p.parseType(argType)))
-        return failure();
-      params.push_back(argType);
-    }
-  } while (succeeded(p.parseOptionalComma()));
-  return p.parseRParen();
-}
-
-static void printFuncTypeArgs(mlir::AsmPrinter &p,
-                              mlir::ArrayRef<mlir::Type> params,
-                              bool isVarArg) {
+  return p.parseCommaSeparatedList(
+      AsmParser::Delimiter::Paren, [&]() -> mlir::ParseResult {
+        if (isVarArg)
+          return p.emitError(p.getCurrentLocation(),
+                             "variadic `...` must be the last parameter");
+        if (succeeded(p.parseOptionalEllipsis())) {
+          isVarArg = true;
+          return success();
+        }
+        mlir::Type type;
+        if (failed(p.parseType(type)))
+          return failure();
+        params.push_back(type);
+        return success();
+      });
+}
+
+static void printFuncTypeParams(mlir::AsmPrinter &p,
+                                mlir::ArrayRef<mlir::Type> params,
+                                bool isVarArg) {
   p << '(';
   llvm::interleaveComma(params, p,
                         [&p](mlir::Type type) { p.printType(type); });
@@ -342,23 +319,6 @@ static void printFuncTypeArgs(mlir::AsmPrinter &p,
   p << ')';
 }
 
-// Use a custom parser to handle the optional return and argument types without
-// an optional anchor.
-static mlir::ParseResult parseFuncType(mlir::AsmParser &p,
-                                       mlir::Type &optionalReturnType,
-                                       llvm::SmallVector<mlir::Type> &params,
-                                       bool &isVarArg) {
-  if (failed(parseFuncTypeArgs(p, params, isVarArg)))
-    return failure();
-  return parseFuncTypeReturn(p, optionalReturnType);
-}
-
-static void printFuncType(mlir::AsmPrinter &p, mlir::Type optionalReturnType,
-                          mlir::ArrayRef<mlir::Type> params, bool isVarArg) {
-  printFuncTypeArgs(p, params, isVarArg);
-  printFuncTypeReturn(p, optionalReturnType);
-}
-
 /// Get the C-style return type of the function, which is !cir.void if the
 /// function returns nothing and the actual return type otherwise.
 mlir::Type FuncType::getReturnType() const {