Add support to trace preparsing decisions

BUG=v8:5501

Review-Url: https://codereview.chromium.org/2424013002
Cr-Commit-Position: refs/heads/master@{#40383}

src/flag-definitions.h

@@ -830,6 +830,7 @@ DEFINE_BOOL(trace_maps, false, "trace map creation")
 // parser.cc
 DEFINE_BOOL(allow_natives_syntax, false, "allow natives syntax")
 DEFINE_BOOL(trace_parse, false, "trace parsing and preparsing")
+DEFINE_BOOL(trace_preparse, false, "trace preparsing decisions")
 DEFINE_BOOL(lazy_inner_functions, false, "enable lazy parsing inner functions")
 
 // simulator-arm.cc, simulator-arm64.cc and simulator-mips.cc

src/parsing/parser.cc

@@ -2696,13 +2696,23 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
       expected_property_count = function_state.expected_property_count();
     }
 
-    if (use_temp_zone || is_lazy_top_level_function) {
+    DCHECK(use_temp_zone || !is_lazy_top_level_function);
+    if (use_temp_zone) {
       // If the preconditions are correct the function body should never be
       // accessed, but do this anyway for better behaviour if they're wrong.
       body = nullptr;
       scope->AnalyzePartially(&previous_zone_ast_node_factory);
     }
 
+    if (FLAG_trace_preparse) {
+      PrintF("  [%s]: %i-%i %.*s\n",
+             is_lazy_top_level_function
+                 ? "Preparse no-resolution"
+                 : (use_temp_zone ? "Preparse resolution" : "Full parse"),
+             scope->start_position(), scope->end_position(),
+             function_name->byte_length(), function_name->raw_data());
+    }
+
     // Parsing the body may change the language mode in our scope.
     language_mode = scope->language_mode();
 

src/parsing/preparser.cc

@@ -177,11 +177,19 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
       is_sloppy(language_mode) && formals.is_simple && !IsConciseMethod(kind);
   ValidateFormalParameters(language_mode, allow_duplicate_parameters, CHECK_OK);
 
+  int end_position = scanner()->location().end_pos;
   if (is_strict(language_mode)) {
-    int end_position = scanner()->location().end_pos;
     CheckStrictOctalLiteral(start_position, end_position, CHECK_OK);
     CheckDecimalLiteralWithLeadingZero(start_position, end_position);
   }
+  function_scope->set_end_position(end_position);
+
+  if (FLAG_trace_preparse) {
+    PrintF("  [%s]: %i-%i\n",
+           track_unresolved_variables_ ? "Preparse resolution"
+                                       : "Preparse no-resolution",
+           function_scope->start_position(), function_scope->end_position());
+  }
 
   return Expression::Default();
 }