[for-in] Sanitize for-in optimizations and fix bailout points.

src/full-codegen/arm64/full-codegen-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 1026 matching lines @@
   SetStatementPosition(stmt, SKIP_BREAK);
 
   FeedbackVectorSlot slot = stmt->ForInFeedbackSlot();
 
   // TODO(all): This visitor probably needs better comments and a revisit.
 
   Label loop, exit;
   ForIn loop_statement(this, stmt);
   increment_loop_depth();
 
-  // Get the object to enumerate over. If the object is null or undefined, skip
-  // over the loop.  See ECMA-262 version 5, section 12.6.4.
+  // Get the object to enumerate over.
   SetExpressionAsStatementPosition(stmt->enumerable());
   VisitForAccumulatorValue(stmt->enumerable());
-  __ JumpIfRoot(x0, Heap::kUndefinedValueRootIndex, &exit);
-  Register null_value = x15;
-  __ LoadRoot(null_value, Heap::kNullValueRootIndex);
-  __ Cmp(x0, null_value);
-  __ B(eq, &exit);
 
-  PrepareForBailoutForId(stmt->PrepareId(), TOS_REG);
-
-  // Convert the object to a JS object.
+  // If the object is null or undefined, skip over the loop, otherwise convert
+  // it to a JS receiver.  See ECMA-262 version 5, section 12.6.4.
   Label convert, done_convert;
   __ JumpIfSmi(x0, &convert);
   __ JumpIfObjectType(x0, x10, x11, FIRST_JS_RECEIVER_TYPE, &done_convert, ge);
+  __ JumpIfRoot(x0, Heap::kNullValueRootIndex, &exit);
+  __ JumpIfRoot(x0, Heap::kUndefinedValueRootIndex, &exit);
   __ Bind(&convert);
   ToObjectStub stub(isolate());
   __ CallStub(&stub);
   __ Bind(&done_convert);
   PrepareForBailoutForId(stmt->ToObjectId(), TOS_REG);
   __ Push(x0);
 
-  // Check for proxies.
-  Label call_runtime;
-  __ JumpIfObjectType(x0, x10, x11, JS_PROXY_TYPE, &call_runtime, eq);
-
   // Check cache validity in generated code. This is a fast case for
   // the JSObject::IsSimpleEnum cache validity checks. If we cannot
   // guarantee cache validity, call the runtime system to check cache
   // validity or get the property names in a fixed array.
-  __ CheckEnumCache(x0, null_value, x10, x11, x12, x13, &call_runtime);
+  // Note: Proxies never have an enum cache, so will always take the
+  // slow path.
+  Label call_runtime;
+  __ CheckEnumCache(x0, x15, x10, x11, x12, x13, &call_runtime);
 
   // The enum cache is valid.  Load the map of the object being
   // iterated over and use the cache for the iteration.
   Label use_cache;
   __ Ldr(x0, FieldMemOperand(x0, HeapObject::kMapOffset));
   __ B(&use_cache);
 
   // Get the set of properties to enumerate.
   __ Bind(&call_runtime);
   __ Push(x0);  // Duplicate the enumerable object on the stack.
@@ skipping 3771 matching lines @@
   }
 
   return INTERRUPT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64