Refactor and clean up array allocation across platforms.

src/x64/builtins-x64.cc

 // Copyright 2011 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 975 matching lines @@
     __ GetBuiltinEntry(rdx, Builtins::CALL_FUNCTION_PROXY);
     __ call(masm->isolate()->builtins()->ArgumentsAdaptorTrampoline(),
             RelocInfo::CODE_TARGET);
 
     // Leave internal frame.
   }
   __ ret(3 * kPointerSize);  // remove this, receiver, and arguments
 }
 
 
-// Number of empty elements to allocate for an empty array.
-static const int kPreallocatedArrayElements = 4;
-
-
 // Allocate an empty JSArray. The allocated array is put into the result
 // register. If the parameter initial_capacity is larger than zero an elements
 // backing store is allocated with this size and filled with the hole values.
 // Otherwise the elements backing store is set to the empty FixedArray.
 static void AllocateEmptyJSArray(MacroAssembler* masm,
                                  Register array_function,
                                  Register result,
                                  Register scratch1,
                                  Register scratch2,
                                  Register scratch3,
-                                 int initial_capacity,
                                  Label* gc_required) {
+  int initial_capacity = JSArray::kPreallocatedArrayElements;
   ASSERT(initial_capacity >= 0);
 
   // Load the initial map from the array function.
   __ movq(scratch1, FieldOperand(array_function,
                                  JSFunction::kPrototypeOrInitialMapOffset));
 
   // Allocate the JSArray object together with space for a fixed array with the
   // requested elements.
   int size = JSArray::kSize;
   if (initial_capacity > 0) {
@@ skipping 38 matching lines @@
   // scratch1: elements array
   // scratch2: start of next object
   __ Move(FieldOperand(scratch1, HeapObject::kMapOffset),
           FACTORY->fixed_array_map());
   __ Move(FieldOperand(scratch1, FixedArray::kLengthOffset),
           Smi::FromInt(initial_capacity));
 
   // Fill the FixedArray with the hole value. Inline the code if short.
   // Reconsider loop unfolding if kPreallocatedArrayElements gets changed.
   static const int kLoopUnfoldLimit = 4;
-  ASSERT(kPreallocatedArrayElements <= kLoopUnfoldLimit);
   __ Move(scratch3, FACTORY->the_hole_value());
   if (initial_capacity <= kLoopUnfoldLimit) {
     // Use a scratch register here to have only one reloc info when unfolding
     // the loop.
     for (int i = 0; i < initial_capacity; i++) {
       __ movq(FieldOperand(scratch1,
                            FixedArray::kHeaderSize + i * kPointerSize),
               scratch3);
     }
   } else {
@@ skipping 13 matching lines @@
 // register array_function holds the built-in Array function and the register
 // array_size holds the size of the array as a smi. The allocated array is put
 // into the result register and beginning and end of the FixedArray elements
 // storage is put into registers elements_array and elements_array_end  (see
 // below for when that is not the case). If the parameter fill_with_holes is
 // true the allocated elements backing store is filled with the hole values
 // otherwise it is left uninitialized. When the backing store is filled the
 // register elements_array is scratched.
 static void AllocateJSArray(MacroAssembler* masm,
                             Register array_function,  // Array function.
-                            Register array_size,  // As a smi.
+                            Register array_size,  // As a smi, cannot be 0.
                             Register result,
                             Register elements_array,
                             Register elements_array_end,
                             Register scratch,
                             bool fill_with_hole,
                             Label* gc_required) {
-  Label not_empty, allocated;
-
   // Load the initial map from the array function.
   __ movq(elements_array,
           FieldOperand(array_function,
                        JSFunction::kPrototypeOrInitialMapOffset));
 
-  // Check whether an empty sized array is requested.
-  __ testq(array_size, array_size);
-  __ j(not_zero, &not_empty);
-
-  // If an empty array is requested allocate a small elements array anyway. This
-  // keeps the code below free of special casing for the empty array.
-  int size = JSArray::kSize + FixedArray::SizeFor(kPreallocatedArrayElements);
-  __ AllocateInNewSpace(size,
-                        result,
-                        elements_array_end,
-                        scratch,
-                        gc_required,
-                        TAG_OBJECT);
-  __ jmp(&allocated);
+  if (FLAG_debug_code) {  // Assert that array size is not zero.
+    Label not_empty;
+    __ testq(array_size, array_size);
+    __ j(not_zero, &not_empty);
+    __ int3();
+    __ bind(&not_empty);
+  }
 
   // Allocate the JSArray object together with space for a FixedArray with the
   // requested elements.
-  __ bind(&not_empty);
   SmiIndex index =
       masm->SmiToIndex(kScratchRegister, array_size, kPointerSizeLog2);
   __ AllocateInNewSpace(JSArray::kSize + FixedArray::kHeaderSize,
                         index.scale,
                         index.reg,
                         result,
                         elements_array_end,
                         scratch,
                         gc_required,
                         TAG_OBJECT);
 
   // Allocated the JSArray. Now initialize the fields except for the elements
   // array.
   // result: JSObject
   // elements_array: initial map
   // elements_array_end: start of next object
   // array_size: size of array (smi)
-  __ bind(&allocated);
   __ movq(FieldOperand(result, JSObject::kMapOffset), elements_array);
   __ Move(elements_array, FACTORY->empty_fixed_array());
   __ movq(FieldOperand(result, JSArray::kPropertiesOffset), elements_array);
   // Field JSArray::kElementsOffset is initialized later.
   __ movq(FieldOperand(result, JSArray::kLengthOffset), array_size);
 
   // Calculate the location of the elements array and set elements array member
   // of the JSArray.
   // result: JSObject
   // elements_array_end: start of next object
   // array_size: size of array (smi)
   __ lea(elements_array, Operand(result, JSArray::kSize));
   __ movq(FieldOperand(result, JSArray::kElementsOffset), elements_array);
 
   // Initialize the fixed array. FixedArray length is stored as a smi.
   // result: JSObject
   // elements_array: elements array
   // elements_array_end: start of next object
   // array_size: size of array (smi)
   __ Move(FieldOperand(elements_array, JSObject::kMapOffset),
           FACTORY->fixed_array_map());
-  Label not_empty_2, fill_array;
-  __ SmiTest(array_size);
-  __ j(not_zero, &not_empty_2);
-  // Length of the FixedArray is the number of pre-allocated elements even
-  // though the actual JSArray has length 0.
-  __ Move(FieldOperand(elements_array, FixedArray::kLengthOffset),
-          Smi::FromInt(kPreallocatedArrayElements));
-  __ jmp(&fill_array);
-  __ bind(&not_empty_2);
   // For non-empty JSArrays the length of the FixedArray and the JSArray is the
   // same.
   __ movq(FieldOperand(elements_array, FixedArray::kLengthOffset), array_size);
 
   // Fill the allocated FixedArray with the hole value if requested.
   // result: JSObject
   // elements_array: elements array
   // elements_array_end: start of next object
-  __ bind(&fill_array);
   if (fill_with_hole) {
     Label loop, entry;
     __ Move(scratch, FACTORY->the_hole_value());
     __ lea(elements_array, Operand(elements_array,
                                    FixedArray::kHeaderSize - kHeapObjectTag));
     __ jmp(&entry);
     __ bind(&loop);
     __ movq(Operand(elements_array, 0), scratch);
     __ addq(elements_array, Immediate(kPointerSize));
     __ bind(&entry);
@@ skipping 12 matching lines @@
 //   rsp[0]: return address
 //   rsp[8]: last argument
 // This function is used for both construct and normal calls of Array. The only
 // difference between handling a construct call and a normal call is that for a
 // construct call the constructor function in rdi needs to be preserved for
 // entering the generic code. In both cases argc in rax needs to be preserved.
 // Both registers are preserved by this code so no need to differentiate between
 // a construct call and a normal call.
 static void ArrayNativeCode(MacroAssembler* masm,
                             Label *call_generic_code) {
-  Label argc_one_or_more, argc_two_or_more;
+  Label argc_one_or_more, argc_two_or_more, empty_array, not_empty_array;
 
   // Check for array construction with zero arguments.
   __ testq(rax, rax);
   __ j(not_zero, &argc_one_or_more);
 
+  __ bind(&empty_array);
   // Handle construction of an empty array.
   AllocateEmptyJSArray(masm,
                        rdi,
                        rbx,
                        rcx,
                        rdx,
                        r8,
-                       kPreallocatedArrayElements,
                        call_generic_code);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->array_function_native(), 1);
   __ movq(rax, rbx);
   __ ret(kPointerSize);
 
   // Check for one argument. Bail out if argument is not smi or if it is
   // negative.
   __ bind(&argc_one_or_more);
   __ cmpq(rax, Immediate(1));
   __ j(not_equal, &argc_two_or_more);
   __ movq(rdx, Operand(rsp, kPointerSize));  // Get the argument from the stack.
+
+  __ SmiTest(rdx);
+  __ j(not_zero, &not_empty_array);
+  __ pop(r8);  // Adjust stack.
+  __ Drop(1);
+  __ push(r8);
+  __ movq(rax, Immediate(0));  // Treat this as a call with argc of zero.
+  __ jmp(&empty_array);
+
+  __ bind(&not_empty_array);
   __ JumpUnlessNonNegativeSmi(rdx, call_generic_code);
 
   // Handle construction of an empty array of a certain size. Bail out if size
   // is to large to actually allocate an elements array.
   __ SmiCompare(rdx, Smi::FromInt(JSObject::kInitialMaxFastElementArray));
   __ j(greater_equal, call_generic_code);
 
   // rax: argc
   // rdx: array_size (smi)
   // rdi: constructor
@@ skipping 325 matching lines @@
   Deoptimizer::EntryGenerator generator(masm, Deoptimizer::OSR);
   generator.Generate();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64