Hydrogenized KeyedLoadGeneric stub: when probing the KeyedLookupCache fails, call the runtime, don'…

src/code-stubs-hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/code-stubs.h"
 #include "src/field-index.h"
 #include "src/hydrogen.h"
 #include "src/lithium.h"
@@ skipping 1636 matching lines @@
 
       ExternalReference cache_keys_ref =
           ExternalReference::keyed_lookup_cache_keys(isolate());
       HValue* cache_keys = Add<HConstant>(cache_keys_ref);
 
       HValue* map = Add<HLoadNamedField>(receiver, static_cast<HValue*>(NULL),
                                          HObjectAccess::ForMap());
       HValue* base_index = AddUncasted<HMul>(hash, Add<HConstant>(2));
       base_index->ClearFlag(HValue::kCanOverflow);
 
-      IfBuilder lookup_if(this);
+      HIfContinuation inline_or_runtime_continuation(
+          graph()->CreateBasicBlock(), graph()->CreateBasicBlock());
+      IfBuilder* lookup_ifs[KeyedLookupCache::kEntriesPerBucket];
       for (int probe = 0; probe < KeyedLookupCache::kEntriesPerBucket;
            ++probe) {
+        IfBuilder* lookup_if = new IfBuilder(this);

[danno, 2014/07/07 07:59:06]

Shouldn't you just Zone allocate this?

void* buffer = zone->New(sizeof(IfBuilder));
IfBuidler* lookup_if = new (buffer) IfBuilder(this)?

[Jakob Kummerow, 2014/07/07 11:52:10]

I'm not sure. In what way would that be better? We never zone-allocate
IfBuilders. And I don't quite see why we should; they're very short-lived
(whereas the graph builder's zone lives "forever"); and we don't need that many
of them (just kEntriesPerBucket == 4).
But if you prefer zone allocation, I can certainly zone-allocate them.

[danno, 2014/07/07 12:08:45]

Well, since we generally avoid allocating from the C++ heap, I personally think
the Zone allocation would be better, but it's your call.

+        lookup_ifs[probe] = lookup_if;
         int probe_base = probe * KeyedLookupCache::kEntryLength;
         HValue* map_index = AddUncasted<HAdd>(base_index,
             Add<HConstant>(probe_base + KeyedLookupCache::kMapIndex));
         map_index->ClearFlag(HValue::kCanOverflow);
         HValue* key_index = AddUncasted<HAdd>(base_index,
             Add<HConstant>(probe_base + KeyedLookupCache::kKeyIndex));
         key_index->ClearFlag(HValue::kCanOverflow);
         HValue* map_to_check = Add<HLoadKeyed>(cache_keys,
                                                map_index,
                                                static_cast<HValue*>(NULL),
                                                FAST_ELEMENTS,
                                                NEVER_RETURN_HOLE, 0);
-        lookup_if.If<HCompareObjectEqAndBranch>(map_to_check, map);
-        lookup_if.And();
+        lookup_if->If<HCompareObjectEqAndBranch>(map_to_check, map);
+        lookup_if->And();
         HValue* key_to_check = Add<HLoadKeyed>(cache_keys,
                                                key_index,
                                                static_cast<HValue*>(NULL),
                                                FAST_ELEMENTS,
                                                NEVER_RETURN_HOLE, 0);
-        lookup_if.If<HCompareObjectEqAndBranch>(key_to_check, key);
-        lookup_if.Then();
+        lookup_if->If<HCompareObjectEqAndBranch>(key_to_check, key);
+        lookup_if->Then();
         {
           ExternalReference cache_field_offsets_ref =
               ExternalReference::keyed_lookup_cache_field_offsets(isolate());
           HValue* cache_field_offsets = Add<HConstant>(cache_field_offsets_ref);
           HValue* index = AddUncasted<HAdd>(hash,
                                             Add<HConstant>(probe));
           index->ClearFlag(HValue::kCanOverflow);
           HValue* property_index = Add<HLoadKeyed>(cache_field_offsets,
                                                    index,
                                                    static_cast<HValue*>(NULL),
                                                    EXTERNAL_INT32_ELEMENTS,
                                                    NEVER_RETURN_HOLE, 0);
           Push(property_index);
         }
-        lookup_if.Else();
+        lookup_if->Else();
       }
-      Add<HDeoptimize>("KeyedLoad fall-back", Deoptimizer::EAGER);
-      Push(graph()->GetConstant0());
-      lookup_if.End();
-      Push(Add<HLoadFieldByIndex>(receiver, Pop()));
+      for (int i = 0; i < KeyedLookupCache::kEntriesPerBucket; ++i) {
+        lookup_ifs[i]->JoinContinuation(&inline_or_runtime_continuation);
+        delete lookup_ifs[i];
+      }
+
+      IfBuilder inline_or_runtime(this, &inline_or_runtime_continuation);
+      inline_or_runtime.Then();
+      {
+        // Found a cached index, load property inline.
+        Push(Add<HLoadFieldByIndex>(receiver, Pop()));
+      }
+      inline_or_runtime.Else();
+      {
+        // KeyedLookupCache miss; call runtime.
+        Add<HPushArguments>(receiver, key);
+        Push(Add<HCallRuntime>(
+            isolate()->factory()->empty_string(),
+            Runtime::FunctionForId(Runtime::kKeyedGetProperty), 2));
+      }
+      inline_or_runtime.End();
     }
     if_dict_properties.End();
   }
   index_name_split.End();
 
   return Pop();
 }
 
 
 Handle<Code> KeyedLoadGenericElementStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
 
 } }  // namespace v8::internal