Do not go to slow mode and back to fast in initializer blocks.

src/x64/full-codegen-x64.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 2100 matching lines @@
   // Non-initializing assignments to consts are ignored.
 }
 
 
 void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
   // Assignment to a property, using a named store IC.
   Property* prop = expr->target()->AsProperty();
   ASSERT(prop != NULL);
   ASSERT(prop->key()->AsLiteral() != NULL);
 
-  // If the assignment starts a block of assignments to the same object,
-  // change to slow case to avoid the quadratic behavior of repeatedly
-  // adding fast properties.
-  if (expr->starts_initialization_block()) {
-    __ push(result_register());
-    __ push(Operand(rsp, kPointerSize));  // Receiver is now under value.
-    __ CallRuntime(Runtime::kToSlowProperties, 1);
-    __ pop(result_register());
-  }
-
   // Record source code position before IC call.
   SetSourcePosition(expr->position());
   __ Move(rcx, prop->key()->AsLiteral()->handle());
-  if (expr->ends_initialization_block()) {
-    __ movq(rdx, Operand(rsp, 0));
-  } else {
-    __ pop(rdx);
-  }
+  __ pop(rdx);
   Handle<Code> ic = is_classic_mode()
       ? isolate()->builtins()->StoreIC_Initialize()
       : isolate()->builtins()->StoreIC_Initialize_Strict();
   CallIC(ic, RelocInfo::CODE_TARGET, expr->AssignmentFeedbackId());
 
-  // If the assignment ends an initialization block, revert to fast case.
-  if (expr->ends_initialization_block()) {
-    __ push(rax);  // Result of assignment, saved even if not needed.
-    __ push(Operand(rsp, kPointerSize));  // Receiver is under value.
-    __ CallRuntime(Runtime::kToFastProperties, 1);
-    __ pop(rax);
-    __ Drop(1);
-  }
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
   context()->Plug(rax);
 }
 
 
 void FullCodeGenerator::EmitKeyedPropertyAssignment(Assignment* expr) {
   // Assignment to a property, using a keyed store IC.
 
-  // If the assignment starts a block of assignments to the same object,
-  // change to slow case to avoid the quadratic behavior of repeatedly
-  // adding fast properties.
-  if (expr->starts_initialization_block()) {
-    __ push(result_register());
-    // Receiver is now under the key and value.
-    __ push(Operand(rsp, 2 * kPointerSize));
-    __ CallRuntime(Runtime::kToSlowProperties, 1);
-    __ pop(result_register());
-  }
-
   __ pop(rcx);
-  if (expr->ends_initialization_block()) {
-    __ movq(rdx, Operand(rsp, 0));  // Leave receiver on the stack for later.
-  } else {
-    __ pop(rdx);
-  }
+  __ pop(rdx);
   // Record source code position before IC call.
   SetSourcePosition(expr->position());
   Handle<Code> ic = is_classic_mode()
       ? isolate()->builtins()->KeyedStoreIC_Initialize()
       : isolate()->builtins()->KeyedStoreIC_Initialize_Strict();
   CallIC(ic, RelocInfo::CODE_TARGET, expr->AssignmentFeedbackId());
 
-  // If the assignment ends an initialization block, revert to fast case.
-  if (expr->ends_initialization_block()) {
-    __ pop(rdx);
-    __ push(rax);  // Result of assignment, saved even if not needed.
-    __ push(rdx);
-    __ CallRuntime(Runtime::kToFastProperties, 1);
-    __ pop(rax);
-  }
-
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
   context()->Plug(rax);
 }
 
 
 void FullCodeGenerator::VisitProperty(Property* expr) {
   Comment cmnt(masm_, "[ Property");
   Expression* key = expr->key();
 
   if (key->IsPropertyName()) {
@@ skipping 2357 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64