[mlir] Escape strings of opaque attributes

[zero9178]

Summary

Opaque attributes that currently contain string literals can't currently be properly roundtripped as they are not printed as escaped strings. This leads to incorrect tokens being generated and the parser to almost certainly fail. This patch simply uses llvm::printEscapedString from LLVM. It escapes all non printable characters and quotes to \xx hex literals, and backslashes to two backslashes. This syntax is supported by MLIRs Lexer as well. The same function is also currently in use for the same purpose in printSymbolReference, printAttribute for StringAttr and many more in AsmPrinter.cpp.

mlir/lib/IR/AsmPrinter.cpp

static void printDialectSymbol(raw_ostream &os, StringRef symPrefix,
 
   // If this symbol name is simple enough, print it directly in pretty form,
   // otherwise, we print it as an escaped string.
   if (isDialectSymbolSimpleEnoughForPrettyForm(symString)) {
     os << '.' << symString;
     return;
   }
 
-  // TODO: escape the symbol name, it could contain " characters.
-  os << "<\"" << symString << "\">";
+  os << "<\"";
+  llvm::printEscapedString(symString, os);
+  os << "\">";
 }
 
 /// Returns true if the given string can be represented as a bare identifier.
 static bool isBareIdentifier(StringRef name) {
   assert(!name.empty() && "invalid name");
 
   // By making this unsigned, the value passed in to isalnum will always be
   // in the range 0-255. This is important when building with MSVC because

mlir/test/IR/parser.mlir

 
 // CHECK-LABEL: func @"\22_string_symbol_reference\22"
 func @"\"_string_symbol_reference\""() {
   // CHECK: ref = @"\22_string_symbol_reference\22"
   "foo.symbol_reference"() {ref = @"\"_string_symbol_reference\""} : () -> ()
   return
 }
 
+// CHECK-LABEL: func private @parse_opaque_attr_escape
+func private @parse_opaque_attr_escape() {
+    // CHECK: value = #foo<"\22escaped\\\0A\22">
+    "foo.constant"() {value = #foo<"\"escaped\\\n\"">} : () -> ()
+}
+
 // CHECK-LABEL: func private @string_attr_name
 // CHECK-SAME: {"0 . 0", nested = {"0 . 0"}}
 func private @string_attr_name() attributes {"0 . 0", nested = {"0 . 0"}}
 
 // CHECK-LABEL: func private @nested_reference
 // CHECK: ref = @some_symbol::@some_nested_symbol
 func private @nested_reference() attributes {test.ref = @some_symbol::@some_nested_symbol }