Implement experimental exponentiation operator via desugaring

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index b1d427e2529f4ec23a4ac702094ba4f874657443..11ecec270a67a122c836e5d429470b1efd344fed 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -511,9 +511,24 @@ bool ParserTraits::ShortcutNumericLiteralBinaryExpression(
         *x = factory->NewNumberLiteral(value, pos);
         return true;
       }
+      case Token::EXP: {
+        double value = power_helper(x_val, y_val);
+        *x = factory->NewNumberLiteral(value, pos);
+        return true;
+      }
       default:
         break;
     }
+  } else if (op == Token::EXP) {
+    Zone* zone = parser_->zone();
+
+    // Desugar exponentiation to runtime call
+    ZoneList<Expression*>* args = new (zone) ZoneList<Expression*>(2, zone);
+    args->Add(*x, zone);
+    args->Add(y, zone);
+    *x = factory->NewCallRuntime(
+        parser_->ast_value_factory()->math_pow_string(), NULL, args, pos);
+    return true;
   }
   return false;
 }
@@ -815,6 +830,7 @@ Parser::Parser(CompilationInfo* info, uintptr_t stack_limit, uint32_t hash_seed,
   set_allow_harmony_computed_property_names(
       FLAG_harmony_computed_property_names);
   set_allow_harmony_rest_params(FLAG_harmony_rest_parameters);
+  set_allow_harmony_exponentiation(FLAG_harmony_exponentiation);
   set_allow_strong_mode(FLAG_strong_mode);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
@@ -4059,6 +4075,8 @@ PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
         allow_harmony_computed_property_names());
     reusable_preparser_->set_allow_harmony_rest_params(
         allow_harmony_rest_params());
+    reusable_preparser_->set_allow_harmony_exponentiation(
+        allow_harmony_exponentiation());
     reusable_preparser_->set_allow_strong_mode(allow_strong_mode());
   }
   PreParser::PreParseResult result = reusable_preparser_->PreParseLazyFunction(