[mlir] Make DenseArrayAttr generic

[Mogball]

Summary

This patch turns DenseArrayBaseAttr into a fully-functional attribute by
adding a generic parser and printer, supporting bool or integer and floating
point element types with bitwidths divisible by 8. It has been renamed
to DenseArrayAttr. The patch maintains the specialized subclasses,
e.g. DenseI32ArrayAttr, which remain the preferred API for accessing
elements in C++.

This allows DenseArrayAttr to hold signed and unsigned integer elements:

array<si8: -128, 127>
array<ui8: 255>

"Exotic" floating point elements:

array<bf16: 1.2, 3.4>

And integers of other bitwidths:

array<i24: 8388607>

[lattner]

This is really great Jeff! Thank you for cleaning this up!

mlir/lib/AsmParser/AttributeParser.cpp

860

I'm pretty sure this is incorrect for big-endian systems, e.g. an i8 is stored in the last 8 bytes of a 64-bit word instead of the first byte. I would implement this with a "extract a byte at a time from the low part of an APInt" loop.

[Mogball]

Use llvm::StoreIntToMemory and llvm::LoadIntFromMemory to handle endianness

[Mogball]

mlir/lib/AsmParser/AttributeParser.cpp

860

Grr you're right. That means the opposite trick in the printer is also incorrect :(. Good catch

[rriddle]

Aside from the getValuesImpl change (which we discussed on another revision), LGTM.

[Mogball]

@mehdi_amini any comments/concerns?

[Mogball]

fix diff

[Mogball]

pull in the fix

[Mogball]

add tests for error cases

[Mogball]

rebase

[mehdi_amini]

@mehdi_amini any comments/concerns?

If you're asking, you could maybe wait at least a day before landing?

This patch turns DenseArrayBaseAttr into a fully-functional attribute by adding a generic parser and printer

I don't know what this means? In general I would rephrase the title as well, the genericity here is fairly limited as far as I can tell (some folks would want an Array of enums :) ).

Otherwise my main concern on the code change right now is that it isn't clear to me what the C++ story is: you added the ability to parse/print some stuff but how do we access / use this on the C++side of things?

[Mogball]

In D132758#3759699, @mehdi_amini wrote:

@mehdi_amini any comments/concerns?

If you're asking, you could maybe wait at least a day before landing?

Sorry >.<. I didn't realize how little time had passed since I posted that comment

This patch turns DenseArrayBaseAttr into a fully-functional attribute by adding a generic parser and printer

I don't know what this means? In general I would rephrase the title as well, the genericity here is fairly limited as far as I can tell (some folks would want an Array of enums :) ).

Yes, you're right that "generic" is too broad a word. It's a little less "generic" than DenseElementsAttr, which allows string elements and integers or any width. On the former point, DenseArrayBaseAttr was on its own not very useful. You needed to use one of the sub-classes. Now, the sub-classes function as more strongly typed "views" on the DenseArrayAttr base class.

Otherwise my main concern on the code change right now is that it isn't clear to me what the C++ story is: you added the ability to parse/print some stuff but how do we access / use this on the C++side of things?

I made some changes to ElementsAttr that would allow DenseArrayAttr to implement, for example, getValues<APInt> and getValues<APFloat>. Coming soon^TM

[mehdi_amini]

In D132758#3759744, @Mogball wrote:

On the former point, DenseArrayBaseAttr was on its own not very useful. You needed to use one of the sub-classes. Now, the sub-classes function as more strongly typed "views" on the DenseArrayAttr base class.

Right but that was very intentional though: making the API hard to misuse is quite important here.

Otherwise my main concern on the code change right now is that it isn't clear to me what the C++ story is: you added the ability to parse/print some stuff but how do we access / use this on the C++side of things?

I made some changes to ElementsAttr that would allow DenseArrayAttr to implement, for example, getValues<APInt> and getValues<APFloat>. Coming soon^TM

OK but ElementsAttr is an interface, and we're back to some convoluted way to access the data. This can't be the main intended way of using this attribute I believe.

[Mogball]

In D132758#3759763, @mehdi_amini wrote:

In D132758#3759744, @Mogball wrote:

On the former point, DenseArrayBaseAttr was on its own not very useful. You needed to use one of the sub-classes. Now, the sub-classes function as more strongly typed "views" on the DenseArrayAttr base class.

Right but that was very intentional though: making the API hard to misuse is quite important here.

I would say it's still quite difficult to misuse. The base attribute is still limited in what it offers out-of-the-box. Adding APInt and APFloat accessors will make interacting with the base class easier while still requiring significant effort to "abuse".

Otherwise my main concern on the code change right now is that it isn't clear to me what the C++ story is: you added the ability to parse/print some stuff but how do we access / use this on the C++side of things?

I made some changes to ElementsAttr that would allow DenseArrayAttr to implement, for example, getValues<APInt> and getValues<APFloat>. Coming soon^TM

OK but ElementsAttr is an interface, and we're back to some convoluted way to access the data. This can't be the main intended way of using this attribute I believe.

I mean you would be able to do DenseArrayAttr::getValues<T> and not go through the interface at all (but the interface would work as well).

[mehdi_amini]

I don't understand why we'd expose any APInt access at all actually? Why should we "exclusively" restrict access to the data through the specialized classes?

[Mogball]

In D132758#3759790, @mehdi_amini wrote:

I don't understand why we'd expose any APInt access at all actually? Why should we "exclusively" restrict access to the data through the specialized classes?

"Should" or "shouldn't"? The specialized classes are still the "preferred" way to interact with the data and the most meaningful way in C++, *if* the data needs to be interacted with in C++.

[mehdi_amini]

In D132758#3759794, @Mogball wrote:

In D132758#3759790, @mehdi_amini wrote:

I don't understand why we'd expose any APInt access at all actually? Why should we "exclusively" restrict access to the data through the specialized classes?

"Should" or "shouldn't"?

"Shouldn't" :)

The specialized classes are still the "preferred" way to interact with the data and the most meaningful way in C++, *if* the data needs to be interacted with in C++.

Right, but the discussion here is only about C++, and you added new in-memory support for this attribute without a good way to manipulate it in C++ as far as I can tell.

[Mogball]

In D132758#3759804, @mehdi_amini wrote:

Right, but the discussion here is only about C++, and you added new in-memory support for this attribute without a good way to manipulate it in C++ as far as I can tell.

I was planning on adding C++ subclasses for the unsigned variants but use APInt/APFloat as the fallback way of interacting with data that don't have great C++ equivalents. Would you instead prefer the parser be restricted even more?

[mehdi_amini]

The whole point of this attribute is to offer a safe API always exposed as ArrayRef<T> with zero ambiguity. Users should never have to lookup the shapes type or anything else there to use it I think.

[Mogball]

Yes, and that hasn't and won't change.

[vitalybuka]

This is broken by the patch https://lab.llvm.org/buildbot/#/builders/5/builds/27136
cc @hctim

[vitalybuka]

There is another one https://lab.llvm.org/buildbot/#/builders/85/builds/10389

I can take a took tomorrow, but I guess it's easy to debug with asserts even without UBsan build.

[mehdi_amini]

@Mogball please prioritize fixing bots after your patch lands: if we can't fix quickly we should always revert quickly.

[Mogball]

I need to check why I'm not getting buildbot emails anymore. I'll look into the failure ASAP (but my UB/ASAN build takes a while)

[Mogball]

I pushed a fix.

[vitalybuka]

In D132758#3764239, @Mogball wrote:

I need to check why I'm not getting buildbot emails anymore. I'll look into the failure ASAP (but my UB/ASAN build takes a while)

That's our fault.
We run check-mlir with sanitizers, but buildbot was not configured to watch that project. So Mlir changes are not on the blame list.
I've changed that yesterday, but it will take time to get from staging to buildbot https://github.com/llvm/llvm-zorg/commit/d96f4ee444459831dbe7de44c859e24b9c06a594

mlir/include/mlir/IR/BuiltinAttributes.h

 namespace mlir {
 //===----------------------------------------------------------------------===//
 // DenseArrayAttr
 
 namespace detail {
 /// Base class for DenseArrayAttr that is instantiated and specialized for each
 /// supported element type below.
 template <typename T>
-class DenseArrayAttr : public DenseArrayBaseAttr {
+class DenseArrayAttrImpl : public DenseArrayAttr {
 public:
-  using DenseArrayBaseAttr::DenseArrayBaseAttr;
+  using DenseArrayAttr::DenseArrayAttr;
 
   /// Implicit conversion to ArrayRef<T>.
   operator ArrayRef<T>() const;
   ArrayRef<T> asArrayRef() const { return ArrayRef<T>{*this}; }
 
   /// Random access to elements.
   T operator[](std::size_t index) const { return asArrayRef()[index]; }
 
   /// Builder from ArrayRef<T>.
-  static DenseArrayAttr get(MLIRContext *context, ArrayRef<T> content);
+  static DenseArrayAttrImpl get(MLIRContext *context, ArrayRef<T> content);
 
   /// Print the short form `[42, 100, -1]` without any type prefix.
   void print(AsmPrinter &printer) const;
   void print(raw_ostream &os) const;
   /// Print the short form `42, 100, -1` without any braces or type prefix.
   void printWithoutBraces(raw_ostream &os) const;
 
   /// Parse the short form `[42, 100, -1]` without any type prefix.
   static Attribute parse(AsmParser &parser, Type type);
 
   /// Parse the short form `42, 100, -1` without any type prefix or braces.
   static Attribute parseWithoutBraces(AsmParser &parser, Type type);
 
   /// Support for isa<>/cast<>.
   static bool classof(Attribute attr);
 };
 
-extern template class DenseArrayAttr<bool>;
-extern template class DenseArrayAttr<int8_t>;
-extern template class DenseArrayAttr<int16_t>;
-extern template class DenseArrayAttr<int32_t>;
-extern template class DenseArrayAttr<int64_t>;
-extern template class DenseArrayAttr<float>;
-extern template class DenseArrayAttr<double>;
+extern template class DenseArrayAttrImpl<bool>;
+extern template class DenseArrayAttrImpl<int8_t>;
+extern template class DenseArrayAttrImpl<int16_t>;
+extern template class DenseArrayAttrImpl<int32_t>;
+extern template class DenseArrayAttrImpl<int64_t>;
+extern template class DenseArrayAttrImpl<float>;
+extern template class DenseArrayAttrImpl<double>;
 } // namespace detail
 
 // Public name for all the supported DenseArrayAttr
-using DenseBoolArrayAttr = detail::DenseArrayAttr<bool>;
-using DenseI8ArrayAttr = detail::DenseArrayAttr<int8_t>;
-using DenseI16ArrayAttr = detail::DenseArrayAttr<int16_t>;
-using DenseI32ArrayAttr = detail::DenseArrayAttr<int32_t>;
-using DenseI64ArrayAttr = detail::DenseArrayAttr<int64_t>;
-using DenseF32ArrayAttr = detail::DenseArrayAttr<float>;
-using DenseF64ArrayAttr = detail::DenseArrayAttr<double>;
+using DenseBoolArrayAttr = detail::DenseArrayAttrImpl<bool>;
+using DenseI8ArrayAttr = detail::DenseArrayAttrImpl<int8_t>;
+using DenseI16ArrayAttr = detail::DenseArrayAttrImpl<int16_t>;
+using DenseI32ArrayAttr = detail::DenseArrayAttrImpl<int32_t>;
+using DenseI64ArrayAttr = detail::DenseArrayAttrImpl<int64_t>;
+using DenseF32ArrayAttr = detail::DenseArrayAttrImpl<float>;
+using DenseF64ArrayAttr = detail::DenseArrayAttrImpl<double>;
 
 //===----------------------------------------------------------------------===//
 // DenseResourceElementsAttr
 
 namespace detail {
 /// Base class for DenseResourceElementsAttr that is instantiated and
 /// specialized for each supported element type below.
 template <typename T>

mlir/include/mlir/IR/BuiltinAttributes.td

auto getAsValueRange() const {
       return llvm::map_range(getAsRange<AttrTy>(), [](AttrTy attr) {
         return static_cast<UnderlyingTy>(attr.getValue());
       });
     }
   }];
 }
 
 //===----------------------------------------------------------------------===//
-// DenseArrayBaseAttr
+// DenseArrayAttr
 //===----------------------------------------------------------------------===//
 
 def Builtin_DenseArrayRawDataParameter : ArrayRefParameter<
     "char", "64-bit aligned storage for dense array elements"> {
   let allocator = [{
     if (!$_self.empty()) {
       auto *alloc = static_cast<char *>(
           $_allocator.allocate($_self.size(), alignof(uint64_t)));
       std::uninitialized_copy($_self.begin(), $_self.end(), alloc);
       $_dst = ArrayRef<char>(alloc, $_self.size());
     }
   }];
 }
 
-def Builtin_DenseArrayBase : Builtin_Attr<
-    "DenseArrayBase", [ElementsAttrInterface, TypedAttrInterface]> {
-  let summary = "A dense array of i8, i16, i32, i64, f32, or f64.";
+def Builtin_DenseArray : Builtin_Attr<
+    "DenseArray", [ElementsAttrInterface, TypedAttrInterface]> {
+  let summary = "A dense array of integer or floating point elements.";
   let description = [{
     A dense array attribute is an attribute that represents a dense array of
     primitive element types. Contrary to DenseIntOrFPElementsAttr this is a
     flat unidimensional array which does not have a storage optimization for
     splat. This allows to expose the raw array through a C++ API as
-    `ArrayRef<T>`. This is the base class attribute, the actual access is
-    intended to be managed through the subclasses `DenseI8ArrayAttr`,
-    `DenseI16ArrayAttr`, `DenseI32ArrayAttr`, `DenseI64ArrayAttr`,
-    `DenseF32ArrayAttr`, and `DenseF64ArrayAttr`.
+    `ArrayRef<T>` for compatible types. The element type must be bool or an
+    integer or float whose bitwidth is a multiple of 8. Bool elements are stored
+    as bytes.
+
+    This is the base class attribute. Access to C++ types is intended to be
+    managed through the subclasses `DenseI8ArrayAttr`, `DenseI16ArrayAttr`,
+    `DenseI32ArrayAttr`, `DenseI64ArrayAttr`, `DenseF32ArrayAttr`,
+    and `DenseF64ArrayAttr`.
 
     Syntax:
 
     ```
-    dense-array-attribute ::= `[` `:` (integer-type | float-type) tensor-literal `]`
+    dense-array-attribute ::= `array` `<` (integer-type | float-type)
+                                          (`:` tensor-literal)? `>`
     ```
     Examples:
 
     ```mlir
     array<i8>
     array<i32: 10, 42>
     array<f64: 42., 12.>
     ```
 
-    when a specific subclass is used as argument of an operation, the declarative
-    assembly will omit the type and print directly:
-    ```
+    When a specific subclass is used as argument of an operation, the
+    declarative assembly will omit the type and print directly:
+
+    ```mlir
     [1, 2, 3]
     ```
   }];
+
   let parameters = (ins
     AttributeSelfTypeParameter<"", "RankedTensorType">:$type,
     Builtin_DenseArrayRawDataParameter:$rawData
   );
+
+  let builders = [
+    AttrBuilderWithInferredContext<(ins "RankedTensorType":$type,
+                                        "ArrayRef<char>":$rawData), [{
+      return $_get(type.getContext(), type, rawData);
+    }]>,
+  ];
+
   let extraClassDeclaration = [{
     /// Allow implicit conversion to ElementsAttr.
     operator ElementsAttr() const {
       return *this ? cast<ElementsAttr>() : nullptr;
     }
 
     /// ElementsAttr implementation.
     using ContiguousIterableTypesT =
         std::tuple<bool, int8_t, int16_t, int32_t, int64_t, float, double>;
     const bool *value_begin_impl(OverloadToken<bool>) const;
     const int8_t *value_begin_impl(OverloadToken<int8_t>) const;
     const int16_t *value_begin_impl(OverloadToken<int16_t>) const;
     const int32_t *value_begin_impl(OverloadToken<int32_t>) const;
     const int64_t *value_begin_impl(OverloadToken<int64_t>) const;
     const float *value_begin_impl(OverloadToken<float>) const;
     const double *value_begin_impl(OverloadToken<double>) const;
-
-    /// Printer for the short form: will dispatch to the appropriate subclass.
-    void print(AsmPrinter &printer) const;
-    void print(raw_ostream &os) const;
-    /// Print the short form `42, 100, -1` without any braces or prefix.
-    void printWithoutBraces(raw_ostream &os) const;
   }];
+
+  let genVerifyDecl = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // DenseIntOrFPElementsAttr
 //===----------------------------------------------------------------------===//
 
 def Builtin_DenseIntOrFPElementsAttr : Builtin_Attr<
     "DenseIntOrFPElements", [ElementsAttrInterface, TypedAttrInterface],

mlir/lib/AsmParser/AttributeParser.cpp

ParseResult TensorLiteralParser::parseList(SmallVectorImpl<int64_t> &dims) {
   // Return the sublists' dimensions with 'size' prepended.
   dims.clear();
   dims.push_back(size);
   dims.append(newDims.begin(), newDims.end());
   return success();
 }
 
 //===----------------------------------------------------------------------===//
-// ElementsAttr Parser
+// DenseArrayAttr Parser
 //===----------------------------------------------------------------------===//
 
 namespace {
-/// This class provides an implementation of AsmParser, allowing to call back
-/// into the libMLIRIR-provided APIs for invoking attribute parsing code defined
-/// in libMLIRIR.
-class CustomAsmParser : public AsmParserImpl<AsmParser> {
+/// A generic dense array element parser. It parsers integer and floating point
+/// elements.
+class DenseArrayElementParser {
 public:
-  CustomAsmParser(Parser &parser)
-      : AsmParserImpl<AsmParser>(parser.getToken().getLoc(), parser) {}
+  explicit DenseArrayElementParser(Type type) : type(type) {}
+
+  /// Parse an integer element.
+  ParseResult parseIntegerElement(Parser &p);
+
+  /// Parse a floating point element.
+  ParseResult parseFloatElement(Parser &p);
+
+  /// Convert the current contents to a dense array.
+  DenseArrayAttr getAttr() {
+    return DenseArrayAttr::get(RankedTensorType::get(size, type), rawData);
+  }
+
+private:
+  /// Append the raw data of an APInt to the result.
+  void append(const APInt &data);
+
+  /// The array element type.
+  Type type;
+  /// The resultant byte array representing the contents of the array.
+  std::vector<char> rawData;
+  /// The number of elements in the array.
+  int64_t size = 0;
 };
 } // namespace
 
+void DenseArrayElementParser::append(const APInt &data) {
+  llvm::append_range(
+      rawData, ArrayRef<char>(reinterpret_cast<const char *>(data.getRawData()),
+                              data.getBitWidth() / 8));
+  ++size;
+}
+
+ParseResult DenseArrayElementParser::parseIntegerElement(Parser &p) {
+  bool isNegative = p.consumeIf(Token::minus);
+
+  // Parse an integer literal as an APInt.
+  Optional<APInt> value;
+  StringRef spelling = p.getToken().getSpelling();
+  if (p.getToken().isAny(Token::kw_true, Token::kw_false)) {
+    if (!type.isInteger(1))
+      return p.emitError("expected i1 type for 'true' or 'false' values");
+    value = APInt(/*numBits=*/8, p.getToken().is(Token::kw_true),
+                  !type.isUnsignedInteger());
+    p.consumeToken();
+  } else if (p.consumeIf(Token::integer)) {
+    value = buildAttributeAPInt(type, isNegative, spelling);
+    if (!value)
+      return p.emitError("integer constant out of range");
+  } else {
+    return p.emitError("expected integer literal");
+  }
+  append(*value);
+  return success();
+}
+
+ParseResult DenseArrayElementParser::parseFloatElement(Parser &p) {
+  bool isNegative = p.consumeIf(Token::minus);
+
+  Token token = p.getToken();
+  Optional<APFloat> result;
+  auto floatType = type.cast<FloatType>();
+  if (p.consumeIf(Token::integer)) {
+    // Parse an integer literal as a float.
+    if (p.parseFloatFromIntegerLiteral(result, token, isNegative,
+                                       floatType.getFloatSemantics(),
+                                       floatType.getWidth()))
+      return failure();
+  } else if (p.consumeIf(Token::floatliteral)) {
+    // Parse a floating point literal.
+    Optional<double> val = token.getFloatingPointValue();
+    if (!val)
+      return failure();
+    result = APFloat(isNegative ? -*val : *val);
+    if (!type.isF64()) {
+      bool unused;
+      result->convert(floatType.getFloatSemantics(),
+                      APFloat::rmNearestTiesToEven, &unused);
+    }
+  } else {
+    return p.emitError("expected integer or floating point literal");
+  }
+
+  append(result->bitcastToAPInt());
+  return success();
+}
+
 /// Parse a dense array attribute.
 Attribute Parser::parseDenseArrayAttr(Type type) {
   consumeToken(Token::kw_array);
-  SMLoc typeLoc = getToken().getLoc();
-  if (parseToken(Token::less, "expected '<' after 'array'") ||
-      (!type && !(type = parseType())))
-    return {};
-  CustomAsmParser parser(*this);
-  Attribute result;
-  // Check for empty list.
-  bool isEmptyList = getToken().is(Token::greater);
-  if (!isEmptyList &&
-      parseToken(Token::colon, "expected ':' after dense array type"))
+  if (parseToken(Token::less, "expected '<' after 'array'"))
     return {};
 
-  if (auto intType = type.dyn_cast<IntegerType>()) {
-    switch (type.getIntOrFloatBitWidth()) {
-    case 1:
-      if (isEmptyList)
-        result = DenseBoolArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseBoolArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    case 8:
-      if (isEmptyList)
-        result = DenseI8ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseI8ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    case 16:
-      if (isEmptyList)
-        result = DenseI16ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseI16ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    case 32:
-      if (isEmptyList)
-        result = DenseI32ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseI32ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    case 64:
-      if (isEmptyList)
-        result = DenseI64ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseI64ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    default:
-      emitError(typeLoc, "expected i1, i8, i16, i32, or i64 but got: ") << type;
-      return {};
-    }
-  } else if (auto floatType = type.dyn_cast<FloatType>()) {
-    switch (type.getIntOrFloatBitWidth()) {
-    case 32:
-      if (isEmptyList)
-        result = DenseF32ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseF32ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    case 64:
-      if (isEmptyList)
-        result = DenseF64ArrayAttr::get(parser.getContext(), {});
-      else
-        result = DenseF64ArrayAttr::parseWithoutBraces(parser, Type{});
-      break;
-    default:
-      emitError(typeLoc, "expected f32 or f64 but got: ") << type;
-      return {};
-    }
+  // Only bool or integer and floating point elements divisible by bytes are
+  // supported.
+  SMLoc typeLoc = getToken().getLoc();
+  if (!type && !(type = parseType()))
+    return {};
+  if (!type.isIntOrIndexOrFloat()) {
+    emitError(typeLoc, "expected integer or float type, got: ") << type;
+  if (!type.isInteger(1) && type.getIntOrFloatBitWidth() % 8 != 0) {
+    emitError(typeLoc, "element type bitwidth must be a multiple of 8");
+
+  // Check for empty list.
+  if (consumeIf(Token::greater))
+    return DenseArrayAttr::get(RankedTensorType::get(0, type), {});
+  if (parseToken(Token::colon, "expected ':' after dense array type"))
+    return {};
+
+  DenseArrayElementParser eltParser(type);
+  if (type.isIntOrIndex()) {
+    if (parseCommaSeparatedList(
+            [&] { return eltParser.parseIntegerElement(*this); }))
+      return {};
   } else {
-    emitError(typeLoc, "expected integer or float type, got: ") << type;
+    if (parseCommaSeparatedList(
+            [&] { return eltParser.parseFloatElement(*this); }))
       return {};
   }
   if (parseToken(Token::greater, "expected '>' to close an array attribute"))
     return {};
-  return result;
+  return eltParser.getAttr();
 }
 
 /// Parse a dense elements attribute.
 Attribute Parser::parseDenseElementsAttr(Type attrType) {
   auto attribLoc = getToken().getLoc();
   consumeToken(Token::kw_dense);
   if (parseToken(Token::less, "expected '<' after 'dense'"))
     return nullptr;

mlir/lib/CAPI/IR/BuiltinAttributes.cpp

MlirAttribute mlirDenseF64ArrayGet(MlirContext ctx, intptr_t size,
   return wrap(
       DenseF64ArrayAttr::get(unwrap(ctx), ArrayRef<double>(values, size)));
 }
 
 //===----------------------------------------------------------------------===//
 // Accessors.
 
 intptr_t mlirDenseArrayGetNumElements(MlirAttribute attr) {
-  return unwrap(attr).cast<DenseArrayBaseAttr>().size();
+  return unwrap(attr).cast<DenseArrayAttr>().size();
 }
 
 //===----------------------------------------------------------------------===//
 // Indexed accessors.
 
 bool mlirDenseBoolArrayGetElement(MlirAttribute attr, intptr_t pos) {
   return unwrap(attr).cast<DenseBoolArrayAttr>()[pos];
 }

mlir/lib/IR/AsmPrinter.cpp

protected:
   /// Print a dense string elements attribute.
   void printDenseStringElementsAttr(DenseStringElementsAttr attr);
 
   /// Print a dense elements attribute. If 'allowHex' is true, a hex string is
   /// used instead of individual elements when the elements attr is large.
   void printDenseIntOrFPElementsAttr(DenseIntOrFPElementsAttr attr,
                                      bool allowHex);
 
+  /// Print a dense array attribute.
+  void printDenseArrayAttr(DenseArrayAttr attr);
+
   void printDialectAttribute(Attribute attr);
   void printDialectType(Type type);
 
   /// Print an escaped string, wrapped with "".
   void printEscapedString(StringRef str);
 
   /// Print a hex string, wrapped with "".
   void printHexString(StringRef str);
if (printerFlags.shouldElideElementsAttr(sparseEltAttr.getIndices()) ||
       DenseIntElementsAttr indices = sparseEltAttr.getIndices();
       if (indices.getNumElements() != 0) {
         printDenseIntOrFPElementsAttr(indices, /*allowHex=*/false);
         os << ", ";
         printDenseElementsAttr(sparseEltAttr.getValues(), /*allowHex=*/true);
       }
       os << '>';
     }
-  } else if (auto denseArrayAttr = attr.dyn_cast<DenseArrayBaseAttr>()) {
+  } else if (auto denseArrayAttr = attr.dyn_cast<DenseArrayAttr>()) {
     typeElision = AttrTypeElision::Must;
     os << "array<" << denseArrayAttr.getType().getElementType();
-    if (!denseArrayAttr.empty())
+    if (!denseArrayAttr.empty()) {
       os << ": ";
-    denseArrayAttr.printWithoutBraces(os);
+      printDenseArrayAttr(denseArrayAttr);
+    }
     os << ">";
   } else if (auto resourceAttr = attr.dyn_cast<DenseResourceElementsAttr>()) {
     os << "dense_resource<";
     printResourceHandle(resourceAttr.getRawHandle());
     os << ">";
   } else if (auto locAttr = attr.dyn_cast<LocationAttr>()) {
     printLocation(locAttr);
   } else {

 
 void AsmPrinter::Impl::printDenseStringElementsAttr(
     DenseStringElementsAttr attr) {
   ArrayRef<StringRef> data = attr.getRawStringData();
   auto printFn = [&](unsigned index) { printEscapedString(data[index]); };
   printDenseElementsAttrImpl(attr.isSplat(), attr.getType(), os, printFn);
 }
 
+void AsmPrinter::Impl::printDenseArrayAttr(DenseArrayAttr attr) {
+  Type type = attr.getElementType();
+  unsigned bitwidth = type.isInteger(1) ? 8 : type.getIntOrFloatBitWidth();
+  ArrayRef<char> data = attr.getRawData();
+
+  auto printElementAt = [&](unsigned i) {
+    // FIXME: The data needs to be padded, requiring an extra copy.
+    SmallVector<char, 8> padded(data.slice(bitwidth / 8 * i, bitwidth / 8));
+    padded.append(
+        APInt::APINT_WORD_SIZE - padded.size() % APInt::APINT_WORD_SIZE, 0);
+    APInt value(type.getIntOrFloatBitWidth(),
+                {reinterpret_cast<const uint64_t *>(padded.data()),
+                 padded.size() / APInt::APINT_WORD_SIZE});
+    // Print the data as-is or as a float.
+    if (type.isIntOrIndex()) {
+      printDenseIntElement(value, getStream(), !type.isUnsignedInteger());
+    } else {
+      APFloat fltVal(type.cast<FloatType>().getFloatSemantics(), value);
+      printFloatValue(fltVal, getStream());
+    }
+  };
+  llvm::interleaveComma(llvm::seq<unsigned>(0, attr.size()), getStream(),
+                        printElementAt);
+}
+
 void AsmPrinter::Impl::printType(Type type) {
   if (!type) {
     os << "<<NULL TYPE>>";
     return;
   }
 
   // Try to print an alias for this type.
   if (state && succeeded(state->getAliasState().getAlias(type, os)))

mlir/lib/IR/BuiltinAttributes.cpp

DenseElementsAttr::ComplexIntElementIterator::operator*() const {
   return {readBits(getData(), offset, bitWidth),
           readBits(getData(), offset + storageWidth, bitWidth)};
 }
 
 //===----------------------------------------------------------------------===//
 // DenseArrayAttr
 //===----------------------------------------------------------------------===//
 
-const bool *DenseArrayBaseAttr::value_begin_impl(OverloadToken<bool>) const {
+LogicalResult
+DenseArrayAttr::verify(function_ref<InFlightDiagnostic()> emitError,
+                       RankedTensorType type, ArrayRef<char> rawData) {
+  if (type.getRank() != 1)
+    return emitError() << "expected rank 1 tensor type";
+  if (!type.getElementType().isIntOrIndexOrFloat())
+    return emitError() << "expected integer or floating point element type";
+  int64_t dataSize = rawData.size();
+  int64_t size = type.getShape().front();
+  if (type.getElementType().isInteger(1)) {
+    if (size != dataSize)
+      return emitError() << "expected " << size
+                         << " bytes for i1 array but got " << dataSize;
+  } else if (size * type.getElementTypeBitWidth() != dataSize * 8) {
+    return emitError() << "expected data size (" << size << " elements, "
+                       << type.getElementTypeBitWidth()
+                       << " bits each) does not match: " << dataSize
+                       << " bytes";
+  }
+  return success();
+}
+
+const bool *DenseArrayAttr::value_begin_impl(OverloadToken<bool>) const {
   return cast<DenseBoolArrayAttr>().asArrayRef().begin();
 }
-const int8_t *
-DenseArrayBaseAttr::value_begin_impl(OverloadToken<int8_t>) const {
+const int8_t *DenseArrayAttr::value_begin_impl(OverloadToken<int8_t>) const {
   return cast<DenseI8ArrayAttr>().asArrayRef().begin();
 }
-const int16_t *
-DenseArrayBaseAttr::value_begin_impl(OverloadToken<int16_t>) const {
+const int16_t *DenseArrayAttr::value_begin_impl(OverloadToken<int16_t>) const {
   return cast<DenseI16ArrayAttr>().asArrayRef().begin();
 }
-const int32_t *
-DenseArrayBaseAttr::value_begin_impl(OverloadToken<int32_t>) const {
+const int32_t *DenseArrayAttr::value_begin_impl(OverloadToken<int32_t>) const {
   return cast<DenseI32ArrayAttr>().asArrayRef().begin();
 }
-const int64_t *
-DenseArrayBaseAttr::value_begin_impl(OverloadToken<int64_t>) const {
+const int64_t *DenseArrayAttr::value_begin_impl(OverloadToken<int64_t>) const {
   return cast<DenseI64ArrayAttr>().asArrayRef().begin();
 }
-const float *DenseArrayBaseAttr::value_begin_impl(OverloadToken<float>) const {
+const float *DenseArrayAttr::value_begin_impl(OverloadToken<float>) const {
   return cast<DenseF32ArrayAttr>().asArrayRef().begin();
 }
-const double *
-DenseArrayBaseAttr::value_begin_impl(OverloadToken<double>) const {
+const double *DenseArrayAttr::value_begin_impl(OverloadToken<double>) const {
   return cast<DenseF64ArrayAttr>().asArrayRef().begin();
 }
 
-void DenseArrayBaseAttr::print(AsmPrinter &printer) const {
-  print(printer.getStream());
-}
-
-void DenseArrayBaseAttr::printWithoutBraces(raw_ostream &os) const {
-  llvm::TypeSwitch<DenseArrayBaseAttr>(*this)
-      .Case<DenseBoolArrayAttr, DenseI8ArrayAttr, DenseI16ArrayAttr,
-            DenseI32ArrayAttr, DenseI64ArrayAttr, DenseF32ArrayAttr,
-            DenseF64ArrayAttr>([&](auto attr) { attr.printWithoutBraces(os); });
-}
-
-void DenseArrayBaseAttr::print(raw_ostream &os) const {
-  os << "[";
-  printWithoutBraces(os);
-  os << "]";
-}
-
 namespace {
 /// Instantiations of this class provide utilities for interacting with native
 /// data types in the context of DenseArrayAttr.
 template <size_t width,
           IntegerType::SignednessSemantics signedness = IntegerType::Signless>
 struct DenseArrayAttrIntUtil {
   static bool checkElementType(Type eltType) {
     auto type = eltType.dyn_cast<IntegerType>();
struct DenseArrayAttrUtil<double> {
   static void printElement(raw_ostream &os, float value) { os << value; }
   static ParseResult parseElement(AsmParser &parser, double &value) {
     return parser.parseFloat(value);
   }
 };
 } // namespace
 
 template <typename T>
-void DenseArrayAttr<T>::print(AsmPrinter &printer) const {
+void DenseArrayAttrImpl<T>::print(AsmPrinter &printer) const {
   print(printer.getStream());
 }
 
 template <typename T>
-void DenseArrayAttr<T>::printWithoutBraces(raw_ostream &os) const {
+void DenseArrayAttrImpl<T>::printWithoutBraces(raw_ostream &os) const {
   llvm::interleaveComma(asArrayRef(), os, [&](T value) {
     DenseArrayAttrUtil<T>::printElement(os, value);
   });
 }
 
 template <typename T>
-void DenseArrayAttr<T>::print(raw_ostream &os) const {
+void DenseArrayAttrImpl<T>::print(raw_ostream &os) const {
   os << "[";
   printWithoutBraces(os);
   os << "]";
 }
 
 /// Parse a DenseArrayAttr without the braces: `1, 2, 3`
 template <typename T>
-Attribute DenseArrayAttr<T>::parseWithoutBraces(AsmParser &parser,
+Attribute DenseArrayAttrImpl<T>::parseWithoutBraces(AsmParser &parser,
                                                     Type odsType) {
   SmallVector<T> data;
   if (failed(parser.parseCommaSeparatedList([&]() {
         T value;
         if (DenseArrayAttrUtil<T>::parseElement(parser, value))
           return failure();
         data.push_back(value);
         return success();
       })))
     return {};
   return get(parser.getContext(), data);
 }
 
 /// Parse a DenseArrayAttr: `[ 1, 2, 3 ]`
 template <typename T>
-Attribute DenseArrayAttr<T>::parse(AsmParser &parser, Type odsType) {
+Attribute DenseArrayAttrImpl<T>::parse(AsmParser &parser, Type odsType) {
   if (parser.parseLSquare())
     return {};
   // Handle empty list case.
   if (succeeded(parser.parseOptionalRSquare()))
     return get(parser.getContext(), {});
   Attribute result = parseWithoutBraces(parser, odsType);
   if (parser.parseRSquare())
     return {};
   return result;
 }
 
 /// Conversion from DenseArrayAttr<T> to ArrayRef<T>.
 template <typename T>
-DenseArrayAttr<T>::operator ArrayRef<T>() const {
+DenseArrayAttrImpl<T>::operator ArrayRef<T>() const {
   ArrayRef<char> raw = getRawData();
   assert((raw.size() % sizeof(T)) == 0);
   return ArrayRef<T>(reinterpret_cast<const T *>(raw.data()),
                      raw.size() / sizeof(T));
 }
 
 /// Builds a DenseArrayAttr<T> from an ArrayRef<T>.
 template <typename T>
-DenseArrayAttr<T> DenseArrayAttr<T>::get(MLIRContext *context,
+DenseArrayAttrImpl<T> DenseArrayAttrImpl<T>::get(MLIRContext *context,
                                                  ArrayRef<T> content) {
   auto shapedType = RankedTensorType::get(
       content.size(), DenseArrayAttrUtil<T>::getElementType(context));
   auto rawArray = ArrayRef<char>(reinterpret_cast<const char *>(content.data()),
                                  content.size() * sizeof(T));
   return Base::get(context, shapedType, rawArray)
-      .template cast<DenseArrayAttr<T>>();
+      .template cast<DenseArrayAttrImpl<T>>();
 }
 
 template <typename T>
-bool DenseArrayAttr<T>::classof(Attribute attr) {
-  if (auto denseArray = attr.dyn_cast<DenseArrayBaseAttr>())
+bool DenseArrayAttrImpl<T>::classof(Attribute attr) {
+  if (auto denseArray = attr.dyn_cast<DenseArrayAttr>())
     return DenseArrayAttrUtil<T>::checkElementType(denseArray.getElementType());
   return false;
 }
 
 namespace mlir {
 namespace detail {
 // Explicit instantiation for all the supported DenseArrayAttr.
-template class DenseArrayAttr<bool>;
-template class DenseArrayAttr<int8_t>;
-template class DenseArrayAttr<int16_t>;
-template class DenseArrayAttr<int32_t>;
-template class DenseArrayAttr<int64_t>;
-template class DenseArrayAttr<float>;
-template class DenseArrayAttr<double>;
+template class DenseArrayAttrImpl<bool>;
+template class DenseArrayAttrImpl<int8_t>;
+template class DenseArrayAttrImpl<int16_t>;
+template class DenseArrayAttrImpl<int32_t>;
+template class DenseArrayAttrImpl<int64_t>;
+template class DenseArrayAttrImpl<float>;
+template class DenseArrayAttrImpl<double>;
 } // namespace detail
 } // namespace mlir
 
 //===----------------------------------------------------------------------===//
 // DenseElementsAttr
 //===----------------------------------------------------------------------===//
 
 /// Method for support type inquiry through isa, cast and dyn_cast.

mlir/test/IR/attribute.mlir

 // CHECK-SAME: i64attr = [-142]
                i64attr = [-142]
 // CHECK-SAME: f32attr = [1.024000e+03, 4.530000e+02, -6.435000e+03]
                f32attr = [1024., 453., -6435.]
 // CHECK-SAME: f64attr = [-1.420000e+02]
                f64attr = [-142.]
 // CHECK-SAME: emptyattr = []
                emptyattr = []
+
+  // CHECK: array.sizes
+  // CHECK-SAME: i0 = array<i0: 0, 0>
+  // CHECK-SAME: ui0 = array<ui0: 0, 0>
+  // CHECK-SAME: si0 = array<si0: 0, 0>
+  // CHECK-SAME: i24 = array<i24: -42, 42, 8388607>
+  // CHECK-SAME: ui24 = array<ui24: 16777215>
+  // CHECK-SAME: si24 = array<si24: -8388608>
+  // CHECK-SAME: bf16 = array<bf16: 1.2{{[0-9]+}}e+00, 3.4{{[0-9]+}}e+00>
+  // CHECK-SAME: f16 = array<f16: 1.{{[0-9]+}}e+00, 3.{{[0-9]+}}e+00>
+  "array.sizes"() {
+    x0_i0 = array<i0: 0, 0>,
+    x1_ui0 = array<ui0: 0, 0>,
+    x2_si0 = array<si0: 0, 0>,
+    x3_i24 = array<i24: -42, 42, 8388607>,
+    x4_ui24 = array<ui24: 16777215>,
+    x5_si24 = array<si24: -8388608>,
+    x6_bf16 = array<bf16: 1.2, 3.4>,
+    x7_f16 = array<f16: 1., 3.>
+  }: () -> ()
   return
 }
 
 // -----
 
 //===----------------------------------------------------------------------===//
 // Test SymbolRefAttr
 //===----------------------------------------------------------------------===//

mlir/test/lib/IR/TestBuiltinAttributeInterfaces.cpp

StringRef getDescription() const final {
     return "Test ElementsAttr interface support.";
   }
   void runOnOperation() override {
     getOperation().walk([&](Operation *op) {
       for (NamedAttribute attr : op->getAttrs()) {
         auto elementsAttr = attr.getValue().dyn_cast<ElementsAttr>();
         if (!elementsAttr)
           continue;
-        if (auto concreteAttr =
-                attr.getValue().dyn_cast<DenseArrayBaseAttr>()) {
-          llvm::TypeSwitch<DenseArrayBaseAttr>(concreteAttr)
+        if (auto concreteAttr = attr.getValue().dyn_cast<DenseArrayAttr>()) {
+          llvm::TypeSwitch<DenseArrayAttr>(concreteAttr)
               .Case([&](DenseBoolArrayAttr attr) {
                 testElementsAttrIteration<bool>(op, attr, "bool");
               })
               .Case([&](DenseI8ArrayAttr attr) {
                 testElementsAttrIteration<int8_t>(op, attr, "int8_t");
               })
               .Case([&](DenseI16ArrayAttr attr) {
                 testElementsAttrIteration<int16_t>(op, attr, "int16_t");