Emit the boilerplate for Attribute printer/parser dialect dispatching from ODS

Add a new `useDefaultAttributePrinterParser` boolean settings on the dialect
(default to false for now) that emits the boilerplate to dispatch attribute
parsing/printing to the auto-generated method.
We will likely turn this on by default in the future.

Differential Revision: https://reviews.llvm.org/D113329

mlir/include/mlir/IR/OpBase.td

@@ -298,6 +298,10 @@ class Dialect {
   // If this dialect overrides the hook for op interface fallback.
   bit hasOperationInterfaceFallback = 0;
 
+  // If this dialect should use default generated attribute parser boilerplate:
+  // it'll dispatch the parsing to every individual attributes directly.
+  bit useDefaultAttributePrinterParser = 0;
+
   // If this dialect overrides the hook for canonicalization patterns.
   bit hasCanonicalizer = 0;
 

mlir/include/mlir/TableGen/Dialect.h

@@ -74,6 +74,10 @@ public:
   /// Returns true if this dialect has fallback interfaces for its operations.
   bool hasOperationInterfaceFallback() const;
 
+  /// Returns true if this dialect should generate the default dispatch for
+  /// attribute printing/parsing.
+  bool useDefaultAttributePrinterParser() const;
+
   // Returns whether two dialects are equal by checking the equality of the
   // underlying record.
   bool operator==(const Dialect &other) const;

mlir/lib/TableGen/Dialect.cpp

@@ -90,6 +90,10 @@ bool Dialect::hasOperationInterfaceFallback() const {
   return def->getValueAsBit("hasOperationInterfaceFallback");
 }
 
+bool Dialect::useDefaultAttributePrinterParser() const {
+  return def->getValueAsBit("useDefaultAttributePrinterParser");
+}
+
 Dialect::EmitPrefix Dialect::getEmitAccessorPrefix() const {
   int prefix = def->getValueAsInt("emitAccessorPrefix");
   if (prefix < 0 || prefix > static_cast<int>(EmitPrefix::Both))

mlir/test/lib/Dialect/Test/TestAttributes.cpp

@@ -229,24 +229,3 @@ void TestDialect::registerAttributes() {
 #include "TestAttrDefs.cpp.inc"
       >();
 }
-
-Attribute TestDialect::parseAttribute(DialectAsmParser &parser,
-                                      Type type) const {
-  StringRef attrTag;
-  if (failed(parser.parseKeyword(&attrTag)))
-    return Attribute();
-  {
-    Attribute attr;
-    auto parseResult = generatedAttributeParser(parser, attrTag, type, attr);
-    if (parseResult.hasValue())
-      return attr;
-  }
-  parser.emitError(parser.getNameLoc(), "unknown test attribute");
-  return Attribute();
-}
-
-void TestDialect::printAttribute(Attribute attr,
-                                 DialectAsmPrinter &printer) const {
-  if (succeeded(generatedAttributePrinter(attr, printer)))
-    return;
-}

mlir/test/lib/Dialect/Test/TestOps.td

@@ -34,6 +34,7 @@ def Test_Dialect : Dialect {
   let hasRegionResultAttrVerify = 1;
   let hasOperationInterfaceFallback = 1;
   let hasNonDefaultDestructor = 1;
+  let useDefaultAttributePrinterParser = 1;
   let dependentDialects = ["::mlir::DLTIDialect"];
 
   let extraClassDeclaration = [{

mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp

@@ -500,6 +500,34 @@ static ::mlir::OptionalParseResult generated{0}Parser(
                                       ::mlir::{0} &value) {{
 )";
 
+/// The code block for default attribute parser/printer dispatch boilerplate.
+/// {0}: the dialect fully qualified class name.
+static const char *const dialectDefaultAttrPrinterParserDispatch = R"(
+/// Parse an attribute registered to this dialect.
+::mlir::Attribute {0}::parseAttribute(::mlir::DialectAsmParser &parser,
+                                      ::mlir::Type type) const {{
+  ::llvm::SMLoc typeLoc = parser.getCurrentLocation();
+  ::llvm::StringRef attrTag;
+  if (failed(parser.parseKeyword(&attrTag)))
+    return {{};
+  {{
+    ::mlir::Attribute attr;
+    auto parseResult = generatedAttributeParser(parser, attrTag, type, attr);
+    if (parseResult.hasValue())
+      return attr;
+  }
+  parser.emitError(typeLoc) << "unknown  attribute `"
+      << attrTag << "` in dialect `" << getNamespace() << "`";
+  return {{};
+}
+/// Print an attribute registered to this dialect.
+void {0}::printAttribute(::mlir::Attribute attr,
+                         ::mlir::DialectAsmPrinter &printer) const {{
+  if (succeeded(generatedAttributePrinter(attr, printer)))
+    return;
+}
+)";
+
 /// The code block used to start the auto-generated printer function.
 ///
 /// {0}: The name of the base value type, e.g. Attribute or Type.
@@ -986,6 +1014,12 @@ bool DefGenerator::emitDefs(StringRef selectedDialect) {
          << "::" << def.getCppClassName() << ")\n";
   }
 
+  // Emit the default parser/printer for Attributes if the dialect asked for it.
+  if (valueType == "Attribute" &&
+      defs.front().getDialect().useDefaultAttributePrinterParser())
+    os << llvm::formatv(dialectDefaultAttrPrinterParserDispatch,
+                        defs.front().getDialect().getCppClassName());
+
   return false;
 }
 

mlir/tools/mlir-tblgen/DialectGen.cpp

@@ -208,7 +208,7 @@ static void emitDialectDecl(Dialect &dialect,
 
     // Check for any attributes/types registered to this dialect.  If there are,
     // add the hooks for parsing/printing.
-    if (!dialectAttrs.empty())
+    if (!dialectAttrs.empty() || dialect.useDefaultAttributePrinterParser())
       os << attrParserDecl;
     if (!dialectTypes.empty())
       os << typeParserDecl;