Generate KeyedLoadDictionaryElementStub with Hydrogen

src/code-stubs-hydrogen.cc

 // Copyright 2012 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 1245 matching lines @@
 
   return js_function;
 }
 
 
 Handle<Code> FastNewClosureStub::GenerateCode(Isolate* isolate) {
   return DoGenerateCode(isolate, this);
 }
 
 
+template <>
+class CodeStubGraphBuilder<KeyedLoadDictionaryElementStub>
+    : public CodeStubGraphBuilderBase {
+ public:
+  explicit CodeStubGraphBuilder(Isolate* isolate,

[Jakob Kummerow, 2013/11/06 10:48:12]

nit: no "explicit" necessary

[danno, 2013/11/15 17:54:09]

Done.

+                                KeyedLoadDictionaryElementStub* stub)
+      : CodeStubGraphBuilderBase(isolate, stub) {}
+
+ protected:
+  HValue* BuildCodeStubHelper(HValue* dictionary,
+                              HValue* key,
+                              HValue* hash,
+                              HValue* mask,
+                              int current_probe);
+
+  virtual HValue* BuildCodeStub();
+
+  KeyedLoadDictionaryElementStub* casted_stub() {
+    return static_cast<KeyedLoadDictionaryElementStub*>(stub());
+  }
+};
+
+
+HValue* CodeStubGraphBuilder<KeyedLoadDictionaryElementStub>::

[Jakob Kummerow, 2013/11/06 10:48:12]

nit: I'd break after "HValue*" instead of after "::", but I leave that up to
you.

[danno, 2013/11/15 17:54:09]

Done.

+    BuildCodeStubHelper(
+    HValue* elements,
+    HValue* key,
+    HValue* hash,
+    HValue* mask,
+    int current_probe) {
+  if (current_probe == kNumberDictionaryProbes) {
+    return NULL;
+  }
+
+  int32_t offset = SeededNumberDictionary::GetProbeOffset(current_probe);
+  HValue* raw_index = (current_probe == 0)
+    ? hash

[Jakob Kummerow, 2013/11/06 10:48:12]

nit: 4 space indent

[danno, 2013/11/15 17:54:09]

Done.

+    : Add<HAdd>(hash, Add<HConstant>(offset));
+  raw_index = Add<HBitwise>(Token::BIT_AND, raw_index, mask);
+  int32_t entry_size = SeededNumberDictionary::kEntrySize;
+  raw_index = Add<HMul>(raw_index, Add<HConstant>(entry_size));
+  raw_index->ClearFlag(HValue::kCanOverflow);
+
+  int32_t base_offset = SeededNumberDictionary::kElementsStartIndex;
+  HValue* key_index = Add<HAdd>(raw_index, Add<HConstant>(base_offset));
+  key_index->ClearFlag(HValue::kCanOverflow);
+
+  HValue* candidate_key = Add<HLoadKeyed>(elements, key_index,
+                                          static_cast<HValue*>(NULL),
+                                          FAST_SMI_ELEMENTS);
+
+  IfBuilder key_compare(this);
+  key_compare.IfNot<HCompareObjectEqAndBranch>(key, candidate_key);
+  key_compare.Then();
+
+  // Key at the current probe doesn't match, try at the next probe.
+  HValue* result = BuildCodeStubHelper(elements, key, hash, mask,
+                                       current_probe + 1);

[mvstanton, 2013/11/04 15:28:24]

The recursive call is interesting here, but the base case is clear:
current_probe == kNumberDictionaryProbes, then deopt if that point is reached.
nice!

[danno, 2013/11/15 17:54:09]

Done.

+  if (result == NULL) {
+    key_compare.Deopt("probes exhausted in keyed load dictionary lookup");
+    result = graph()->GetConstantUndefined();

[Jakob Kummerow, 2013/11/06 10:48:12]

As discussed, the automatic environment padding handles this, but I'd weakly
prefer Push()ing some value (undefined, 0, take your pick) explicitly.

[danno, 2013/11/15 17:54:09]

Done.

+  } else {
+    Push(result);
+  }
+
+  key_compare.Else();
+  // Key at current probe matches. Details must be zero, otherwise the
+  // dictionary element requires special handling.
+  HValue* details_index = Add<HAdd>(raw_index,
+                                    Add<HConstant>(base_offset + 2));
+  details_index->ClearFlag(HValue::kCanOverflow);
+
+  HValue* details = Add<HLoadKeyed>(elements, details_index,
+                                    static_cast<HValue*>(NULL),
+                                    FAST_SMI_ELEMENTS);
+  IfBuilder details_compare(this);
+  details_compare.If<HCompareNumericAndBranch>(details,
+                                               graph()->GetConstant0(),
+                                               Token::NE);
+  details_compare.ThenDeopt("keyed load dictionary element not fast case");
+
+  details_compare.Else();
+  // Key matches and details are zero --> fast case. Load and return the value.
+  HValue* result_index = Add<HAdd>(raw_index,
+                                   Add<HConstant>(base_offset + 1));
+  result_index->ClearFlag(HValue::kCanOverflow);
+
+  Push(Add<HLoadKeyed>(elements, result_index,
+                       static_cast<HValue*>(NULL),
+                       FAST_ELEMENTS));
+
+  details_compare.End();

[mvstanton, 2013/11/04 15:28:24]

nit: I would engage in the { } indentation style here like BinaryOpStub and
FastNewClosureStub because it would be easier to parse the control flow.

[danno, 2013/11/15 17:54:09]

Done.

+
+  key_compare.End();
+
+  return Pop();
+}
+
+
+HValue* CodeStubGraphBuilder<KeyedLoadDictionaryElementStub>::BuildCodeStub() {
+  KeyedLoadDictionaryElementStub* stub = casted_stub();
+
+  HValue* dictionary = GetParameter(0);
+  HValue* key = GetParameter(1);
+  USE(stub);

[mvstanton, 2013/11/04 15:28:24]

What are the USE statements for, can they be removed?

[danno, 2013/11/15 17:54:09]

Done.

+  USE(dictionary);
+
+  HValue* elements = AddLoadElements(dictionary);
+
+  Add<HCheckSmi>(key);
+
+  HValue* hash = BuildElementIndexHash(key);
+
+  HValue* capacity = Add<HLoadKeyed>(
+      elements,
+      Add<HConstant>(NameDictionary::kCapacityIndex),
+      static_cast<HValue*>(NULL),
+      FAST_SMI_ELEMENTS);
+
+  HValue* mask = Add<HSub>(capacity, graph()->GetConstant1());
+  mask->ChangeRepresentation(Representation::Integer32());
+  mask->ClearFlag(HValue::kCanOverflow);
+
+  return BuildCodeStubHelper(elements, key, hash, mask, 0);
+}
+
+
+Handle<Code> KeyedLoadDictionaryElementStub::GenerateCode(Isolate* isolate) {
+  return DoGenerateCode(isolate, this);
+}
+
+
 } }  // namespace v8::internal