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

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index de09516cc3580ff73bbd5ceafee0f273d2b96030..8ff3e9330457826f5f202412344bc44e8680934e 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -2183,43 +2183,16 @@ void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
   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());
-    __ ldr(ip, MemOperand(sp, kPointerSize));  // Receiver is now under value.
-    __ push(ip);
-    __ CallRuntime(Runtime::kToSlowProperties, 1);
-    __ pop(result_register());
-  }
-
   // Record source code position before IC call.
   SetSourcePosition(expr->position());
   __ mov(r2, Operand(prop->key()->AsLiteral()->handle()));
-  // Load receiver to r1. Leave a copy in the stack if needed for turning the
-  // receiver into fast case.
-  if (expr->ends_initialization_block()) {
-    __ ldr(r1, MemOperand(sp));
-  } else {
-    __ pop(r1);
-  }
+  __ pop(r1);
 
   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(r0);  // Result of assignment, saved even if not needed.
-    // Receiver is under the result value.
-    __ ldr(ip, MemOperand(sp, kPointerSize));
-    __ push(ip);
-    __ CallRuntime(Runtime::kToFastProperties, 1);
-    __ pop(r0);
-    __ Drop(1);
-  }
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
   context()->Plug(r0);
 }
@@ -2228,44 +2201,16 @@ void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
 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.
-    __ ldr(ip, MemOperand(sp, 2 * kPointerSize));
-    __ push(ip);
-    __ CallRuntime(Runtime::kToSlowProperties, 1);
-    __ pop(result_register());
-  }
-
   // Record source code position before IC call.
   SetSourcePosition(expr->position());
   __ pop(r1);  // Key.
-  // Load receiver to r2. Leave a copy in the stack if needed for turning the
-  // receiver into fast case.
-  if (expr->ends_initialization_block()) {
-    __ ldr(r2, MemOperand(sp));
-  } else {
-    __ pop(r2);
-  }
+  __ pop(r2);
 
   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()) {
-    __ push(r0);  // Result of assignment, saved even if not needed.
-    // Receiver is under the result value.
-    __ ldr(ip, MemOperand(sp, kPointerSize));
-    __ push(ip);
-    __ CallRuntime(Runtime::kToFastProperties, 1);
-    __ pop(r0);
-    __ Drop(1);
-  }
   PrepareForBailoutForId(expr->AssignmentId(), TOS_REG);
   context()->Plug(r0);
 }