Hydrogen array constructor cleanup and improvements

src/x64/code-stubs-x64.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 3721 matching lines @@
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
   __ cmpq(rcx, rdi);
   __ j(equal, &done);
   __ Cmp(rcx, TypeFeedbackCells::MegamorphicSentinel(isolate));
   __ j(equal, &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(isolate,
-                                                  LAST_FAST_ELEMENTS_KIND);
   __ JumpIfNotSmi(rcx, &miss);
-  __ Cmp(rcx, terminal_kind_sentinel);
-  __ j(above, &miss);
   // Make sure the function is the Array() function
   __ LoadArrayFunction(rcx);
   __ cmpq(rdi, rcx);
   __ j(not_equal, &megamorphic);
   __ jmp(&done);
 
   __ bind(&miss);
 
   // A monomorphic miss (i.e, here the cache is not uninitialized) goes
   // megamorphic.
@@ skipping 3036 matching lines @@
   __ movq(rcx, Operand(rsp, kPointerSize));
   __ testq(rcx, rcx);
   __ j(zero, &normal_sequence);
 
   // We are going to create a holey array, but our kind is non-holey.
   // Fix kind and retry
   __ incl(rdx);
   __ Cmp(rbx, undefined_sentinel);
   __ j(equal, &normal_sequence);
 
+  // The type cell may have gone megamorphic, don't overwrite if so
+  __ movq(rcx, FieldOperand(rbx, kPointerSize));
+  __ JumpIfNotSmi(rcx, &normal_sequence);
+
   // Save the resulting elements kind in type info
   __ Integer32ToSmi(rdx, rdx);
   __ movq(FieldOperand(rbx, kPointerSize), rdx);
   __ SmiToInteger32(rdx, rdx);
 
   __ bind(&normal_sequence);
   int last_index = GetSequenceIndexFromFastElementsKind(
       TERMINAL_FAST_ELEMENTS_KIND);
   for (int i = 0; i <= last_index; ++i) {
     Label next;
@@ skipping 210 matching lines @@
   __ bind(&fast_elements_case);
   GenerateCase(masm, FAST_ELEMENTS);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64