[mlir] Make StringRefParameter roundtrippable (#65813)

The current printer of `StringRefParameter` simply prints out the
content of the string as is without escaping it any way. This leads to
it generating invalid syntax, causing parser errors when read in again.

This PR fixes that by adding `printString` to `AsmPrinter`, allowing one
to print a string that can be parsed with `parseString`, using the same
escaping syntax as `StringAttr`.

mlir/include/mlir/IR/AttrTypeBase.td

@@ -363,7 +363,7 @@ class DefaultValuedParameter<string type, string value, string desc = ""> :
 class StringRefParameter<string desc = "", string value = ""> :
     AttrOrTypeParameter<"::llvm::StringRef", desc> {
   let allocator = [{$_dst = $_allocator.copyInto($_self);}];
-  let printer = [{$_printer << '"' << $_self << '"';}];
+  let printer = [{$_printer.printString($_self);}];
   let cppStorageType = "std::string";
   let defaultValue = value;
 }

mlir/include/mlir/IR/OpImplementation.h

@@ -184,6 +184,10 @@ public:
   /// has any special or non-printable characters in it.
   virtual void printKeywordOrString(StringRef keyword);
 
+  /// Print the given string as a quoted string, escaping any special or
+  /// non-printable characters in it.
+  virtual void printString(StringRef string);
+
   /// Print the given string as a symbol reference, i.e. a form representable by
   /// a SymbolRefAttr. A symbol reference is represented as a string prefixed
   /// with '@'. The reference is surrounded with ""'s and escaped if it has any

mlir/lib/IR/AsmPrinter.cpp

@@ -779,6 +779,7 @@ private:
     os << "%";
   }
   void printKeywordOrString(StringRef) override {}
+  void printString(StringRef) override {}
   void printResourceHandle(const AsmDialectResourceHandle &) override {}
   void printSymbolName(StringRef) override {}
   void printSuccessor(Block *) override {}
@@ -919,6 +920,7 @@ private:
   /// determining potential aliases.
   void printFloat(const APFloat &) override {}
   void printKeywordOrString(StringRef) override {}
+  void printString(StringRef) override {}
   void printSymbolName(StringRef) override {}
   void printResourceHandle(const AsmDialectResourceHandle &) override {}
 
@@ -2767,6 +2769,13 @@ void AsmPrinter::printKeywordOrString(StringRef keyword) {
   ::printKeywordOrString(keyword, impl->getStream());
 }
 
+void AsmPrinter::printString(StringRef keyword) {
+  assert(impl && "expected AsmPrinter::printString to be overriden");
+  *this << '"';
+  printEscapedString(keyword, getStream());
+  *this << '"';
+}
+
 void AsmPrinter::printSymbolName(StringRef symbolRef) {
   assert(impl && "expected AsmPrinter::printSymbolName to be overriden");
   ::printSymbolReference(symbolRef, impl->getStream());

mlir/test/mlir-tblgen/attr-or-type-format-roundtrip.mlir

@@ -70,6 +70,7 @@ attributes {
 // CHECK: !test.optional_type_string
 // CHECK: !test.optional_type_string
 // CHECK: !test.optional_type_string<"non default">
+// CHECK: !test.optional_type_string<"containing\0A \22escape\22 characters\0F">
 
 func.func private @test_roundtrip_default_parsers_struct(
   !test.no_parser<255, [1, 2, 3, 4, 5], "foobar", 4>
@@ -111,5 +112,6 @@ func.func private @test_roundtrip_default_parsers_struct(
   !test.custom_type_string<"bar" bar>,
   !test.optional_type_string,
   !test.optional_type_string<"default">,
-  !test.optional_type_string<"non default">
+  !test.optional_type_string<"non default">,
+  !test.optional_type_string<"containing\n \"escape\" characters\0f">
 )