Make setting length on arrays faster.

src/arm/ic-arm.cc

 // Copyright 2006-2008 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 840 matching lines @@
   // -----------------------------------
 
   __ push(r1);
   __ stm(db_w, sp, r2.bit() | r0.bit());
 
   // Perform tail call to the entry.
   __ TailCallRuntime(ExternalReference(IC_Utility(kStoreIC_Miss)), 3, 1);
 }
 
 
+void StoreIC::GenerateArrayLength(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- r0    : value
+  //  -- r1    : receiver
+  //  -- r2    : name
+  //  -- lr    : return address
+  // -----------------------------------
+  //
+  // This accepts as a receiver anything JSObject::SetElementsLength accepts
+  // (currently anything except for external and pixel arrays which means
+  // anything with elements of FixedArray type.), but currently is restricted
+  // to JSArray.
+  // Value must be a number, but only smis are accepted as the most common case.
+
+  Label miss;
+
+  Register receiver = r1;
+  Register value = r0;
+  Register scratch = r3;
+
+  // Check that the receiver isn't a smi.
+  __ BranchOnSmi(receiver, &miss);
+
+  // Check that the object is a JS array.
+  __ CompareObjectType(receiver, scratch, scratch, JS_ARRAY_TYPE);
+  __ b(ne, &miss);
+
+  // Check that elements are FixedArray.
+  __ ldr(scratch, FieldMemOperand(receiver, JSArray::kElementsOffset));
+  __ CompareObjectType(scratch, scratch, scratch, FIXED_ARRAY_TYPE);
+  __ b(ne, &miss);
+
+  // Check that value is a smi.
+  __ BranchOnNotSmi(value, &miss);
+
+  // Prepare tail call to StoreIC_ArrayLength.
+  __ push(receiver);
+  __ push(value);
+
+  __ TailCallRuntime(ExternalReference(IC_Utility(kStoreIC_ArrayLength)), 2, 1);
+
+  __ bind(&miss);
+
+  GenerateMiss(masm);
+}
+
+
 #undef __
 
 
 } }  // namespace v8::internal