Cache IC handlers on the prototype's map if possible

src/ia32/stub-cache-ia32.cc

Index: src/ia32/stub-cache-ia32.cc
diff --git a/src/ia32/stub-cache-ia32.cc b/src/ia32/stub-cache-ia32.cc
index a35be80deffac906f522aa68d8d5eb4f46e987e3..b6e2dc145da434e98ba3062322c709e557d88de1 100644
--- a/src/ia32/stub-cache-ia32.cc
+++ b/src/ia32/stub-cache-ia32.cc
@@ -823,6 +823,11 @@ Register StubCompiler::CheckPrototypes(Handle<HeapType> type,
       __ mov(reg, FieldOperand(scratch1, Map::kPrototypeOffset));
     } else {
       bool in_new_space = heap()->InNewSpace(*prototype);
+      // Two possible reasons for loading the prototype from the map:
+      // (1) Can't store references to new space in code.
+      // (2) Handler is shared for all receivers with the same prototype
+      //     map (but not necessarily the same prototype instance).
+      bool load_prototype_from_map = in_new_space || depth == 1;
       if (depth != 1 || check == CHECK_ALL_MAPS) {
         __ CheckMap(reg, current_map, miss, DONT_DO_SMI_CHECK);
       }
@@ -838,19 +843,16 @@ Register StubCompiler::CheckPrototypes(Handle<HeapType> type,
             scratch2, miss);
       }
 
-      if (in_new_space) {
+      if (load_prototype_from_map) {
         // Save the map in scratch1 for later.
         __ mov(scratch1, FieldOperand(reg, HeapObject::kMapOffset));
       }
 
       reg = holder_reg;  // From now on the object will be in holder_reg.
 
-      if (in_new_space) {
-        // The prototype is in new space; we cannot store a reference to it
-        // in the code.  Load it from the map.
+      if (load_prototype_from_map) {
         __ mov(reg, FieldOperand(scratch1, Map::kPrototypeOffset));
       } else {
-        // The prototype is in old space; load it directly.
         __ mov(reg, prototype);
       }
     }