First implementation of allocation elimination in Hydrogen.

src/ia32/lithium-codegen-ia32.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 740 matching lines @@
     case ARGUMENTS_ADAPTOR:
       translation->BeginArgumentsAdaptorFrame(closure_id, translation_size);
       break;
     case STUB:
       translation->BeginCompiledStubFrame();
       break;
     default:
       UNREACHABLE();
   }
 
+  int object_index = 0;
+  int dematerialized_index = 0;
   for (int i = 0; i < translation_size; ++i) {
     LOperand* value = environment->values()->at(i);
-
-    // TODO(mstarzinger): Introduce marker operands to indicate that this value
-    // is not present and must be reconstructed from the deoptimizer. Currently
-    // this is only used for the arguments object.
-    if (value == NULL) {
-      int arguments_count = environment->values()->length() - translation_size;
-      translation->BeginArgumentsObject(arguments_count);
-      for (int i = 0; i < arguments_count; ++i) {
-        LOperand* value = environment->values()->at(translation_size + i);
-        AddToTranslation(translation,
-                         value,
-                         environment->HasTaggedValueAt(translation_size + i),
-                         environment->HasUint32ValueAt(translation_size + i));
-      }
-      continue;
-    }
-
-    AddToTranslation(translation,
+    AddToTranslation(environment,
+                     translation,
                      value,
                      environment->HasTaggedValueAt(i),
-                     environment->HasUint32ValueAt(i));
+                     environment->HasUint32ValueAt(i),
+                     &object_index,
+                     &dematerialized_index);
   }
 }
 
 
-void LCodeGen::AddToTranslation(Translation* translation,
+void LCodeGen::AddToTranslation(LEnvironment* environment,
+                                Translation* translation,
                                 LOperand* op,
                                 bool is_tagged,
-                                bool is_uint32) {
+                                bool is_uint32,
+                                int* object_index_pointer,
+                                int* dematerialized_index_pointer) {
+  if (op == LEnvironment::materialization_marker()) {
+    int object_index = (*object_index_pointer)++;
+    if (environment->ObjectIsDuplicateAt(object_index)) {

[titzer, 2013/08/01 17:11:50]

ObjectDuplicate means...object reference?

[Michael Starzinger, 2013/08/05 15:13:00]

Correct. It means that a previously translated object is referenced again by
another slot (either on the stack or inside another dematerialized object). I
can rename all uses of "duplicated object" to "referenced object" if you think
that clarifies the situation. Let me know.

+      int dupe_of = environment->ObjectDuplicateOfAt(object_index);
+      translation->DuplicateObject(dupe_of);
+      return;
+    }
+    int object_length = environment->ObjectLengthAt(object_index);
+    if (environment->ObjectIsArgumentsAt(object_index)) {
+      translation->BeginArgumentsObject(object_length);
+    } else {
+      translation->BeginCapturedObject(object_length);
+    }
+    int dematerialized_index = *dematerialized_index_pointer;
+    int env_offset = environment->translation_size() + dematerialized_index;
+    *dematerialized_index_pointer += object_length;
+    for (int i = 0; i < object_length; ++i) {
+      LOperand* value = environment->values()->at(env_offset + i);
+      AddToTranslation(environment,
+                       translation,
+                       value,
+                       environment->HasTaggedValueAt(env_offset + i),
+                       environment->HasUint32ValueAt(env_offset + i),
+                       object_index_pointer,
+                       dematerialized_index_pointer);
+    }
+    return;
+  }
+
   if (op->IsStackSlot()) {
     if (is_tagged) {
       translation->StoreStackSlot(op->index());
     } else if (is_uint32) {
       translation->StoreUint32StackSlot(op->index());
     } else {
       translation->StoreInt32StackSlot(op->index());
     }
   } else if (op->IsDoubleStackSlot()) {
     translation->StoreDoubleStackSlot(op->index());
@@ skipping 5727 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32