Add support for empty hydrogen filter that matches only the top-level JSFunction.

BUG=

Review URL: https://codereview.chromium.org/19590002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15729 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -212,7 +212,7 @@ DEFINE_bool(string_slices, true, "use string slices")
 
 // Flags for Crankshaft.
 DEFINE_bool(crankshaft, true, "use crankshaft")
-DEFINE_string(hydrogen_filter, "", "optimization filter")
+DEFINE_string(hydrogen_filter, "*", "optimization filter")
 DEFINE_bool(use_range, true, "use hydrogen range analysis")
 DEFINE_bool(use_gvn, true, "use hydrogen global value numbering")
 DEFINE_bool(use_canonicalizing, true, "use hydrogen instruction canonicalizing")

src/objects.cc

@@ -9646,8 +9646,16 @@ Context* JSFunction::NativeContextFromLiterals(FixedArray* literals) {
 
 bool JSFunction::PassesHydrogenFilter() {
   String* name = shared()->DebugName();
-  if (*FLAG_hydrogen_filter != '\0') {
+  // The filter string is a pattern that matches functions in this way:
+  //   "*"      all; the default
+  //   "-"      all but the top-level function
+  //   "-name"  all but the function "name"
+  //   ""       only the top-level function
+  //   "name"   only the function "name"
+  //   "name*"  only functions starting with "name"
+  if (*FLAG_hydrogen_filter != '*') {
     Vector<const char> filter = CStrVector(FLAG_hydrogen_filter);
+    if (filter.length() == 0) return name->length() == 0;
     if (filter[0] != '-' && name->IsUtf8EqualTo(filter)) return true;
     if (filter[0] == '-' &&
         !name->IsUtf8EqualTo(filter.SubVector(1, filter.length()))) {