Introduce basic type feedback for for-in statements to avoid deopts.

src/arm/full-codegen-arm.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 986 matching lines @@
   __ push(r0);  // Map.
   __ ldr(r1, FieldMemOperand(r2, FixedArray::kLengthOffset));
   __ mov(r0, Operand(Smi::FromInt(0)));
   // Push enumeration cache, enumeration cache length (as smi) and zero.
   __ Push(r2, r1, r0);
   __ jmp(&loop);
 
   // We got a fixed array in register r0. Iterate through that.
   Label non_proxy;
   __ bind(&fixed_array);
+
+  Handle<JSGlobalPropertyCell> cell =
+      isolate()->factory()->NewJSGlobalPropertyCell(
+          Handle<Object>(
+              Smi::FromInt(TypeFeedbackCells::kForInFastCaseMarker)));
+  RecordTypeFeedbackCell(stmt->PrepareId(), cell);
+  __ LoadHeapObject(r1, cell);
+  __ mov(r2, Operand(Smi::FromInt(TypeFeedbackCells::kForInSlowCaseMarker)));
+  __ str(r2, FieldMemOperand(r1, JSGlobalPropertyCell::kValueOffset));
+
   __ mov(r1, Operand(Smi::FromInt(1)));  // Smi indicates slow check
   __ ldr(r2, MemOperand(sp, 0 * kPointerSize));  // Get enumerated object
   STATIC_ASSERT(FIRST_JS_PROXY_TYPE == FIRST_SPEC_OBJECT_TYPE);
   __ CompareObjectType(r2, r3, r3, LAST_JS_PROXY_TYPE);
   __ b(gt, &non_proxy);
   __ mov(r1, Operand(Smi::FromInt(0)));  // Zero indicates proxy
   __ bind(&non_proxy);
   __ Push(r1, r0);  // Smi and array
   __ ldr(r1, FieldMemOperand(r0, FixedArray::kLengthOffset));
   __ mov(r0, Operand(Smi::FromInt(0)));
@@ skipping 3374 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM