[mlir] load dialects for non-namespaced attrs (#96242)

The mlir-translate tool calls into the parser without loading registered
dependent dialects, and the parser only loads attributes if the
fully-namespaced attribute is present in the textual IR. This causes
parsing to break when an op has an attribute that prints/parses without
the namespaced attribute.

Co-authored-by: Jeremy Kun <jkun@google.com>

mlir/test/IR/parser.mlir

@@ -1465,3 +1465,14 @@ test.dialect_custom_format_fallback custom_format_fallback
 // CHECK: test.format_optional_result_d_op : f80
 test.format_optional_result_d_op : f80
 
+
+// -----
+
+// This is a testing that a non-qualified attribute in a custom format
+// correctly preload the dialect before creating the attribute.
+#attr = #test.nested_polynomial<<1 + x**2>>
+// CHECK-lABLE: @parse_correctly
+llvm.func @parse_correctly() {
+  test.containing_int_polynomial_attr #attr
+  llvm.return
+}

mlir/test/lib/Dialect/Test/CMakeLists.txt

@@ -16,8 +16,8 @@ mlir_tablegen(TestOpInterfaces.cpp.inc -gen-op-interface-defs)
 add_public_tablegen_target(MLIRTestInterfaceIncGen)
 
 set(LLVM_TARGET_DEFINITIONS TestOps.td)
-mlir_tablegen(TestAttrDefs.h.inc -gen-attrdef-decls)
-mlir_tablegen(TestAttrDefs.cpp.inc -gen-attrdef-defs)
+mlir_tablegen(TestAttrDefs.h.inc -gen-attrdef-decls -attrdefs-dialect=test)
+mlir_tablegen(TestAttrDefs.cpp.inc -gen-attrdef-defs -attrdefs-dialect=test)
 add_public_tablegen_target(MLIRTestAttrDefIncGen)
 
 set(LLVM_TARGET_DEFINITIONS TestTypeDefs.td)
@@ -86,6 +86,7 @@ add_mlir_library(MLIRTestDialect
   MLIRLinalgTransforms
   MLIRLLVMDialect
   MLIRPass
+  MLIRPolynomialDialect
   MLIRReduce
   MLIRTensorDialect
   MLIRTransformUtils

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

@@ -16,6 +16,7 @@
 // To get the test dialect definition.
 include "TestDialect.td"
 include "TestEnumDefs.td"
+include "mlir/Dialect/Polynomial/IR/PolynomialAttributes.td"
 include "mlir/Dialect/Utils/StructuredOpsUtils.td"
 include "mlir/IR/AttrTypeBase.td"
 include "mlir/IR/BuiltinAttributeInterfaces.td"
@@ -351,4 +352,12 @@ def TestCustomFloatAttr : Test_Attr<"TestCustomFloat"> {
   }];
 }
 
+def NestedPolynomialAttr : Test_Attr<"NestedPolynomialAttr"> {
+  let mnemonic = "nested_polynomial";
+  let parameters = (ins Polynomial_IntPolynomialAttr:$poly);
+  let assemblyFormat = [{
+    `<` $poly `>`
+  }];
+}
+
 #endif // TEST_ATTRDEFS

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

@@ -17,6 +17,7 @@
 #include <tuple>
 
 #include "TestTraits.h"
+#include "mlir/Dialect/Polynomial/IR/PolynomialAttributes.h"
 #include "mlir/Dialect/Utils/StructuredOpsUtils.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/Diagnostics.h"

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

@@ -232,6 +232,11 @@ def FloatElementsAttrOp : TEST_Op<"float_elements_attr"> {
   );
 }
 
+def ContainingIntPolynomialAttrOp : TEST_Op<"containing_int_polynomial_attr"> {
+  let arguments = (ins NestedPolynomialAttr:$attr);
+  let assemblyFormat = "$attr attr-dict";
+}
+
 // A pattern that updates dense<[3.0, 4.0]> to dense<[5.0, 6.0]>.
 // This tests both matching and generating float elements attributes.
 def UpdateFloatElementsAttr : Pat<
@@ -2215,7 +2220,7 @@ def ForwardBufferOp : TEST_Op<"forward_buffer", [Pure]> {
 def ReifyBoundOp : TEST_Op<"reify_bound", [Pure]> {
   let description = [{
     Reify a bound for the given index-typed value or dimension size of a shaped
-    value. "LB", "EQ" and "UB" bounds are supported. If `scalable` is set, 
+    value. "LB", "EQ" and "UB" bounds are supported. If `scalable` is set,
     `vscale_min` and `vscale_max` must be provided, which allows computing
     a bound in terms of "vector.vscale" for a given range of vscale.
   }];

mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp

@@ -164,8 +164,9 @@ static const char *const parserErrorStr =
 /// {2}: Code template for printing an error.
 /// {3}: Name of the attribute or type.
 /// {4}: C++ class of the parameter.
+/// {5}: Optional code to preload the dialect for this variable.
 static const char *const variableParser = R"(
-// Parse variable '{0}'
+// Parse variable '{0}'{5}
 _result_{0} = {1};
 if (::mlir::failed(_result_{0})) {{
   {2}"failed to parse {3} parameter '{0}' which is to be a `{4}`");
@@ -411,9 +412,28 @@ void DefFormat::genVariableParser(ParameterElement *el, FmtContext &ctx,
   auto customParser = param.getParser();
   auto parser =
       customParser ? *customParser : StringRef(defaultParameterParser);
+
+  // If the variable points to a dialect specific entity (type of attribute),
+  // we force load the dialect now before trying to parse it.
+  std::string dialectLoading;
+  if (auto *defInit = dyn_cast<llvm::DefInit>(param.getDef())) {
+    auto *dialectValue = defInit->getDef()->getValue("dialect");
+    if (dialectValue) {
+      if (auto *dialectInit =
+              dyn_cast<llvm::DefInit>(dialectValue->getValue())) {
+        Dialect dialect(dialectInit->getDef());
+        auto cppNamespace = dialect.getCppNamespace();
+        std::string name = dialect.getCppClassName();
+        dialectLoading = ("\nodsParser.getContext()->getOrLoadDialect<" +
+                          cppNamespace + "::" + name + ">();")
+                             .str();
+      }
+    }
+  }
   os << formatv(variableParser, param.getName(),
                 tgfmt(parser, &ctx, param.getCppStorageType()),
-                tgfmt(parserErrorStr, &ctx), def.getName(), param.getCppType());
+                tgfmt(parserErrorStr, &ctx), def.getName(), param.getCppType(),
+                dialectLoading);
 }
 
 void DefFormat::genParamsParser(ParamsDirective *el, FmtContext &ctx,