Some optimizations for packer.js.

src/runtime.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2338 matching lines @@
 
   return Smi::FromInt(str1_length - str2_length);
 }
 
 
 static Object* Runtime_SubString(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 3);
 
   CONVERT_CHECKED(String, value, args[0]);
-  CONVERT_DOUBLE_CHECKED(from_number, args[1]);
-  CONVERT_DOUBLE_CHECKED(to_number, args[2]);
+  Object* from = args[1];
+  Object* to = args[2];
+  if (from->IsSmi() && to->IsSmi()) {

[Søren Thygesen Gjesse, 2009/11/19 21:42:57]

Maybe add a comment to this fast case.

+    int start = Smi::cast(from)->value();
+    int end = Smi::cast(to)->value();
 

[Søren Thygesen Gjesse, 2009/11/19 21:42:57]

Please move the declaration of start and end before the if and the following
four lines after the else block to avoid commin code in if and else block.

-  int start = FastD2I(from_number);
-  int end = FastD2I(to_number);
+    RUNTIME_ASSERT(end >= start);
+    RUNTIME_ASSERT(start >= 0);
+    RUNTIME_ASSERT(end <= value->length());
+    return value->SubString(start, end);
+  } else {
+    CONVERT_DOUBLE_CHECKED(from_number, from);
+    CONVERT_DOUBLE_CHECKED(to_number, to);
 
-  RUNTIME_ASSERT(end >= start);
-  RUNTIME_ASSERT(start >= 0);
-  RUNTIME_ASSERT(end <= value->length());
-  return value->SubString(start, end);
+    int start = FastD2I(from_number);
+    int end = FastD2I(to_number);
+
+    RUNTIME_ASSERT(end >= start);
+    RUNTIME_ASSERT(start >= 0);
+    RUNTIME_ASSERT(end <= value->length());
+    return value->SubString(start, end);
+  }
 }
 
 
 static Object* Runtime_StringMatch(Arguments args) {
   ASSERT_EQ(3, args.length());
 
   CONVERT_ARG_CHECKED(String, subject, 0);
   CONVERT_ARG_CHECKED(JSRegExp, regexp, 1);
   CONVERT_ARG_CHECKED(JSArray, regexp_info, 2);
   HandleScope handles;
@@ skipping 5524 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal