Hydrogen array constructor cleanup and improvements

src/arm/code-stubs-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 4629 matching lines @@
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
   __ cmp(r3, r1);
   __ b(eq, &done);
   __ CompareRoot(r3, Heap::kUndefinedValueRootIndex);
   __ b(eq, &done);
 
   // Special handling of the Array() function, which caches not only the
   // monomorphic Array function but the initial ElementsKind with special
   // sentinels
-  Handle<Object> terminal_kind_sentinel =
-      TypeFeedbackCells::MonomorphicArraySentinel(masm->isolate(),
-                                                  LAST_FAST_ELEMENTS_KIND);
   __ JumpIfNotSmi(r3, &miss);
-  __ cmp(r3, Operand(terminal_kind_sentinel));
-  __ b(gt, &miss);
   // Make sure the function is the Array() function
   __ LoadArrayFunction(r3);
   __ cmp(r1, r3);
   __ b(ne, &megamorphic);
   __ jmp(&done);
 
   __ bind(&miss);
 
   // A monomorphic miss (i.e, here the cache is not uninitialized) goes
   // megamorphic.
@@ skipping 2519 matching lines @@
   __ ldr(r5, MemOperand(sp, 0));
   __ cmp(r5, Operand::Zero());
   __ b(eq, &normal_sequence);
 
   // We are going to create a holey array, but our kind is non-holey.
   // Fix kind and retry
   __ add(r3, r3, Operand(1));
   __ cmp(r2, Operand(undefined_sentinel));
   __ b(eq, &normal_sequence);
 
+  // The type cell may have gone megamorphic, don't overwrite if so
+  __ ldr(r5, FieldMemOperand(r2, kPointerSize));
+  __ JumpIfNotSmi(r5, &normal_sequence);
+
   // Save the resulting elements kind in type info
   __ SmiTag(r3);
   __ str(r3, FieldMemOperand(r2, kPointerSize));
   __ SmiUntag(r3);
 
   __ bind(&normal_sequence);
   int last_index = GetSequenceIndexFromFastElementsKind(
       TERMINAL_FAST_ELEMENTS_KIND);
   for (int i = 0; i <= last_index; ++i) {
     Label next;
@@ skipping 206 matching lines @@
   __ bind(&fast_elements_case);
   GenerateCase(masm, FAST_ELEMENTS);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM