[mlir][ods] Add description to Attr and ensure doc generation

[ftynse]

Summary

Add the description textual field to the Attr ODS class to mirror an
identical field in the Type ODS class. Add support for generating
documentation for attribute constraints defined using this field. This
ensures mlir-tblgen produces at least some documentation for dialects
that only define attribute constraints, such as DLTI.

[ftynse]

Actually add the test.

[rriddle]

mlir/tools/mlir-tblgen/OpDocGen.cpp

374

Can you spell out auto here?

392

Should we be inserting into dialectsWithDocs here as well?

[ftynse]

Address review.

mlir/include/mlir/IR/OpBase.td

 //===----------------------------------------------------------------------===//
 // Attribute definitions
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
 // Base attribute definition
 
 // Base class for all attributes.
-class Attr<Pred condition, string descr = ""> :
-    AttrConstraint<condition, descr> {
+class Attr<Pred condition, string summary = ""> :
+    AttrConstraint<condition, summary> {
   code storageType = ?; // The backing mlir::Attribute type
   code returnType = ?;  // The underlying C++ value type
 
   // The call expression to convert from the storage type to the return
   // type. For example, an enum can be stored as an int but returned as an
   // enum class.
   //
   // Format: $_self will be expanded to the attribute.
class Attr<Pred condition, string summary = ""> :
   // This can be used for getting its name; otherwise, we will see
   // "anonymous_<number>" as the attribute def name because of template
   // instantiation.
   // TOOD(b/132458159): deduplicate the fields in attribute wrapper classes.
   Attr baseAttr = ?;
 
   // The fully-qualified C++ namespace where the generated class lives.
   string cppNamespace = "";
+
+  // The full description of this attribute.
+  string description = "";
 }
 
 // An attribute of a specific dialect.
-class DialectAttr<Dialect d, Pred condition, string descr = ""> :
-    Attr<condition, descr> {
+class DialectAttr<Dialect d, Pred condition, string summary = ""> :
+    Attr<condition, summary> {
   Dialect dialect = d;
   let cppNamespace = d.cppNamespace;
 }
 
 //===----------------------------------------------------------------------===//
 // Attribute modifier definition
 
 // Decorates an attribute to have an (unvalidated) default value if not present.

mlir/include/mlir/TableGen/Attribute.h

public:
   StringRef getAttrDefName() const;
 
   // Returns the code body for derived attribute. Aborts if this is not a
   // derived attribute.
   StringRef getDerivedCodeBody() const;
 
   // Returns the dialect for the attribute if defined.
   Dialect getDialect() const;
+
+  // Returns the description of the attribute.
+  StringRef getDescription() const;
 };
 
 // Wrapper class providing helper methods for accessing MLIR constant attribute
 // defined in TableGen. This class should closely reflect what is defined as
 // class `ConstantAttr` in TableGen.
 class ConstantAttr {
 public:
   explicit ConstantAttr(const llvm::DefInit *init);

mlir/lib/TableGen/Attribute.cpp

Dialect Attribute::getDialect() const {
   const llvm::RecordVal *record = def->getValue("dialect");
   if (record && record->getValue()) {
     if (DefInit *init = dyn_cast<DefInit>(record->getValue()))
       return Dialect(init->getDef());
   }
   return Dialect(nullptr);
 }
 
+StringRef Attribute::getDescription() const {
+  return def->getValueAsString("description");
+}
+
 ConstantAttr::ConstantAttr(const DefInit *init) : def(init->getDef()) {
   assert(def->isSubClassOf("ConstantAttr") &&
          "must be subclass of TableGen 'ConstantAttr' class");
 }
 
 Attribute ConstantAttr::getAttribute() const {
   return Attribute(def->getValueAsDef("attr"));
 }

mlir/test/mlir-tblgen/gen-dialect-doc.td

 // RUN: mlir-tblgen -gen-dialect-doc -I %S/../../include %s | FileCheck %s
 
 include "mlir/IR/OpBase.td"
 include "mlir/Interfaces/SideEffectInterfaces.td"
 
 def Test_Dialect : Dialect {
   let name = "test";
   let summary = "Dialect of ops to test";
   let description = [{
     Dialect without a [TOC] here.
     TOC added by tool.
   }];
   let cppNamespace = "NS";
 }
 def AOp : Op<Test_Dialect, "a", [NoSideEffect, SingleBlockImplicitTerminator<"YieldOp">]>;
 
+def TestAttr : DialectAttr<Test_Dialect, CPred<"true">> {
+  let summary = "attribute summary";
+  let description = "attribute description";
+}
+
+def TestType : DialectType<Test_Dialect, CPred<"true">> {
+  let summary = "type summary";
+  let description = "type description";
+}
+
 // CHECK: Dialect without a [TOC] here.
 // CHECK: TOC added by tool.
 // CHECK: [TOC]
+
+// CHECK: ## Attribute constraint definition
+// CHECK: ### attribute summary
+// CHECK: attribute description
+
+// CHECK: ## Type constraint definition
+// CHECK: ### type summary
+// CHECK: type description
+
 // CHECK-NOT: [TOC]
 // CHECK: Traits: SingleBlockImplicitTerminator<YieldOp>
 // CHECK: Interfaces: NoSideEffect (MemoryEffectOpInterface)
 // CHECK: Effects: MemoryEffects::Effect{}
 
 def Toc_Dialect : Dialect {
   let name = "test_toc";
   let summary = "Dialect of ops to test";

mlir/tools/mlir-tblgen/OpDocGen.cpp

static void emitOpDoc(const RecordKeeper &recordKeeper, raw_ostream &os) {
   auto opDefs = getRequestedOpDefinitions(recordKeeper);
 
   os << "<!-- Autogenerated by mlir-tblgen; don't manually edit -->\n";
   for (const llvm::Record *opDef : opDefs)
     emitOpDoc(Operator(opDef), os);
 }
 
 //===----------------------------------------------------------------------===//
+// Attribute Documentation
+//===----------------------------------------------------------------------===//
+
+static void emitAttrDoc(const Attribute &attr, raw_ostream &os) {
+  os << "### " << attr.getSummary() << "\n\n";
+  emitDescription(attr.getDescription(), os);
+  os << "\n\n";
+}
+
+//===----------------------------------------------------------------------===//
 // Type Documentation
 //===----------------------------------------------------------------------===//
 
 static void emitTypeDoc(const Type &type, raw_ostream &os) {
-  os << "### " << type.getSummary() << "\n";
+  os << "### " << type.getSummary() << "\n\n";
   emitDescription(type.getDescription(), os);
-  os << "\n";
+  os << "\n\n";
 }
 
 //===----------------------------------------------------------------------===//
 // TypeDef Documentation
 //===----------------------------------------------------------------------===//
 
 static void emitAttrOrTypeDefAssemblyFormat(const AttrOrTypeDef &def,
                                             raw_ostream &os) {
static void emitAttrOrTypeDefDoc(const RecordKeeper &recordKeeper,
   for (const llvm::Record *def : defs)
     emitAttrOrTypeDefDoc(AttrOrTypeDef(def), os);
 }
 
 //===----------------------------------------------------------------------===//
 // Dialect Documentation
 //===----------------------------------------------------------------------===//
 
-static void emitDialectDoc(const Dialect &dialect, ArrayRef<AttrDef> attrDefs,
-                           ArrayRef<Operator> ops, ArrayRef<Type> types,
-                           ArrayRef<TypeDef> typeDefs, raw_ostream &os) {
+static void emitDialectDoc(const Dialect &dialect,
+                           ArrayRef<Attribute> attributes,
+                           ArrayRef<AttrDef> attrDefs, ArrayRef<Operator> ops,
+                           ArrayRef<Type> types, ArrayRef<TypeDef> typeDefs,
+                           raw_ostream &os) {
   if (selectedDialect.getNumOccurrences() &&
       dialect.getName() != selectedDialect)
     return;
   os << "# '" << dialect.getName() << "' Dialect\n\n";
   emitIfNotEmpty(dialect.getSummary(), os);
   emitIfNotEmpty(dialect.getDescription(), os);
 
   // Generate a TOC marker except if description already contains one.
   llvm::Regex r("^[[:space:]]*\\[TOC\\]$", llvm::Regex::RegexFlags::Newline);
   if (!r.match(dialect.getDescription()))
     os << "[TOC]\n\n";
 
+  if (!attributes.empty()) {
+    os << "## Attribute constraint definition\n\n";
+    for (const Attribute &attr : attributes)
+      emitAttrDoc(attr, os);
+  }
+
   if (!attrDefs.empty()) {
     os << "## Attribute definition\n\n";
     for (const AttrDef &def : attrDefs)
       emitAttrOrTypeDefDoc(def, os);
   }
 
   // TODO: Add link between use and def for types
   if (!types.empty()) {
if (!typeDefs.empty()) {
     os << "## Type definition\n\n";
     for (const TypeDef &def : typeDefs)
       emitAttrOrTypeDefDoc(def, os);
   }
 }
 
 static void emitDialectDoc(const RecordKeeper &recordKeeper, raw_ostream &os) {
   std::vector<Record *> opDefs = getRequestedOpDefinitions(recordKeeper);
+  std::vector<Record *> attrDefs =
+      recordKeeper.getAllDerivedDefinitionsIfDefined("DialectAttr");
   std::vector<Record *> typeDefs =
       recordKeeper.getAllDerivedDefinitionsIfDefined("DialectType");
   std::vector<Record *> typeDefDefs =
       recordKeeper.getAllDerivedDefinitionsIfDefined("TypeDef");
   std::vector<Record *> attrDefDefs =
       recordKeeper.getAllDerivedDefinitionsIfDefined("AttrDef");
 
   std::set<Dialect> dialectsWithDocs;
 
+  llvm::StringMap<std::vector<Attribute>> dialectAttrs;
   llvm::StringMap<std::vector<AttrDef>> dialectAttrDefs;
   llvm::StringMap<std::vector<Operator>> dialectOps;
   llvm::StringMap<std::vector<Type>> dialectTypes;
   llvm::StringMap<std::vector<TypeDef>> dialectTypeDefs;
+  for (auto *attrDef : attrDefs) {
+    Attribute attr(attrDef);
+    if (auto dialect = attr.getDialect()) {
+      dialectAttrs[dialect.getName()].push_back(attr);
+      dialectsWithDocs.insert(dialect);
+    }
+  }
   for (auto *attrDef : attrDefDefs) {
     AttrDef attr(attrDef);
     dialectAttrDefs[attr.getDialect().getName()].push_back(attr);
     dialectsWithDocs.insert(attr.getDialect());
   }
   for (auto *opDef : opDefs) {
     Operator op(opDef);
     dialectOps[op.getDialect().getName()].push_back(op);
     dialectsWithDocs.insert(op.getDialect());
   }
   for (auto *typeDef : typeDefs) {
     Type type(typeDef);
     if (auto dialect = type.getDialect())
       dialectTypes[dialect.getName()].push_back(type);
   }
   for (auto *typeDef : typeDefDefs) {
     TypeDef type(typeDef);
     dialectTypeDefs[type.getDialect().getName()].push_back(type);
     dialectsWithDocs.insert(type.getDialect());
   }
 
   os << "<!-- Autogenerated by mlir-tblgen; don't manually edit -->\n";
   for (const Dialect &dialect : dialectsWithDocs) {
     StringRef dialectName = dialect.getName();
-    emitDialectDoc(dialect, dialectAttrDefs[dialectName],
-                   dialectOps[dialectName], dialectTypes[dialectName],
-                   dialectTypeDefs[dialectName], os);
+    emitDialectDoc(dialect, dialectAttrs[dialectName],
+                   dialectAttrDefs[dialectName], dialectOps[dialectName],
+                   dialectTypes[dialectName], dialectTypeDefs[dialectName], os);
   }
 }
 
 //===----------------------------------------------------------------------===//
 // Gen Registration
 //===----------------------------------------------------------------------===//
 
 static mlir::GenRegistration