[mlir][AsmPrinter] Properly escape strings when printing locations

[rriddle]

Summary

This fixes errors when location strings contains newlines, or other non-ascii characters.

mlir/lib/IR/AsmPrinter.cpp

TypeSwitch<LocationAttr>(loc)
       })
       .Case<UnknownLoc>([&](UnknownLoc loc) {
         if (pretty)
           os << "[unknown]";
         else
           os << "unknown";
       })
       .Case<FileLineColLoc>([&](FileLineColLoc loc) {
-        StringRef mayQuote = pretty ? "" : "\"";
-        os << mayQuote << loc.getFilename() << mayQuote << ':' << loc.getLine()
-           << ':' << loc.getColumn();
+        if (pretty) {
+          os << loc.getFilename();
+        } else {
+          os << "\"";
+          printEscapedString(loc.getFilename(), os);
+          os << "\"";
+        }
+        os << ':' << loc.getLine() << ':' << loc.getColumn();
       })
       .Case<NameLoc>([&](NameLoc loc) {
-        os << '\"' << loc.getName() << '\"';
+        os << '\"';
+        printEscapedString(loc.getName(), os);
+        os << '\"';
 
         // Print the child if it isn't unknown.
         auto childLoc = loc.getChildLoc();
         if (!childLoc.isa<UnknownLoc>()) {
           os << '(';
           printLocationInternal(childLoc, pretty);
           os << ')';
         }

mlir/test/IR/locations.mlir

func @inline_notation() -> i32 {
 
   // CHECK: return %0 : i32 loc(unknown)
   return %1 : i32 loc(unknown)
 }
 
 // CHECK-LABEL: func private @loc_attr(i1 {foo.loc_attr = loc(callsite("foo" at "mysource.cc":10:8))})
 func private @loc_attr(i1 {foo.loc_attr = loc(callsite("foo" at "mysource.cc":10:8))})
 
+  // Check that locations get properly escaped.
+// CHECK-LABEL: func @escape_strings()
+func @escape_strings() {
+  // CHECK: loc("escaped\0A")
+  "foo"() : () -> () loc("escaped\n")
+
+  // CHECK: loc("escaped\0A")
+  "foo"() : () -> () loc("escaped\0A")
+
+  // CHECK: loc("escaped\0A":0:0)
+  "foo"() : () -> () loc("escaped\n":0:0)
+  return
+}
+
 // CHECK-ALIAS: "foo.op"() : () -> () loc(#[[LOC:.*]])
 "foo.op"() : () -> () loc(#loc)
 
 // CHECK-ALIAS: #[[LOC]] = loc("out_of_line_location")
 #loc = loc("out_of_line_location")