Add parser support for internal named attributes. These are attributes with names starting with ':'.

PiperOrigin-RevId: 235774810

mlir/g3doc/LangRef.md

@@ -867,7 +867,7 @@ Syntax:
 ``` {.ebnf}
 attribute-dict ::= `{` `}`
                  | `{` attribute-entry (`,` attribute-entry)* `}`
-attribute-entry ::= bare-id `:` attribute-value
+attribute-entry ::= `:`? bare-id `:` attribute-value
 ```
 
 Attributes are the mechanism for specifying constant data in MLIR in places

mlir/lib/IR/AsmPrinter.cpp

@@ -1022,8 +1022,8 @@ void ModulePrinter::printOptionalAttrDict(ArrayRef<NamedAttribute> attrs,
   SmallVector<NamedAttribute, 8> filteredAttrs;
   for (auto attr : attrs) {
     auto attrName = attr.first.strref();
-    // Never print attributes that start with a colon.  These are internal
-    // attributes that represent location or other internal metadata.
+    // By default, never print attributes that start with a colon.  These are
+    // attributes represent location or other internal metadata.
     if (!printInternalAttributes && attrName.startswith(":"))
       return;
 

mlir/lib/Parser/Parser.cpp

@@ -1433,7 +1433,7 @@ ParseResult Parser::parseLocationInstance(llvm::Optional<Location> *loc) {
 ///
 ///   attribute-dict ::= `{` `}`
 ///                    | `{` attribute-entry (`,` attribute-entry)* `}`
-///   attribute-entry ::= bare-id `:` attribute-value
+///   attribute-entry ::= `:`? bare-id `:` attribute-value
 ///
 ParseResult
 Parser::parseAttributeDict(SmallVectorImpl<NamedAttribute> &attributes) {
@@ -1441,11 +1441,17 @@ Parser::parseAttributeDict(SmallVectorImpl<NamedAttribute> &attributes) {
     return ParseFailure;
 
   auto parseElt = [&]() -> ParseResult {
+    // Check for an internal attribute.
+    bool isInternalAttr = consumeIf(Token::colon);
+
     // We allow keywords as attribute names.
     if (getToken().isNot(Token::bare_identifier, Token::inttype) &&
         !getToken().isKeyword())
       return emitError("expected attribute name");
-    auto nameId = builder.getIdentifier(getTokenSpelling());
+    Identifier nameId =
+        isInternalAttr
+            ? builder.getIdentifier(Twine(":" + getTokenSpelling()).str())
+            : builder.getIdentifier(getTokenSpelling());
     consumeToken();
 
     if (parseToken(Token::colon, "expected ':' in attribute list"))

mlir/test/IR/parser.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s | FileCheck %s
+// RUN: mlir-opt -mlir-print-internal-attributes %s | FileCheck %s
 
 // CHECK-DAG: #map{{[0-9]+}} = (d0, d1, d2, d3, d4)[s0] -> (d0, d1, d2, d4, d3)
 #map0 = (d0, d1, d2, d3, d4)[s0] -> (d0, d1, d2, d4, d3)
@@ -802,3 +802,10 @@ func @unregistered_term(%arg0 : i1) -> i1 {
 ^bb1(%arg1 : i1):
   return %arg1 : i1
 }
+
+// CHECK-LABEL: func @internal_attrs
+func @internal_attrs()
+    // CHECK-NEXT: attributes  {:internal.attr: 10
+    attributes {:internal.attr: 10} {
+  return
+}