[stubs] Introduce a dedicated FastNewObjectStub.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index b4b9e3a20c5e3a635048c836758a154263911cb6..239eddd28efddd577ab0dd07e6425f6780f6ddb0 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -4561,6 +4561,131 @@ void InternalArrayConstructorStub::Generate(MacroAssembler* masm) {
 }
 
 
+void FastNewObjectStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- r1 : target
+  //  -- r3 : new target
+  //  -- cp : context
+  //  -- lr : return address
+  // -----------------------------------
+  __ AssertFunction(r1);
+  __ AssertReceiver(r3);
+
+  // Verify that the new target is a JSFunction.
+  Label new_object;
+  __ CompareObjectType(r3, r2, r2, JS_FUNCTION_TYPE);
+  __ b(ne, &new_object);
+
+  // Load the initial map and verify that it's in fact a map.
+  __ ldr(r2, FieldMemOperand(r3, JSFunction::kPrototypeOrInitialMapOffset));
+  __ JumpIfSmi(r2, &new_object);
+  __ CompareObjectType(r2, r0, r0, MAP_TYPE);
+  __ b(ne, &new_object);
+
+  // Fall back to runtime if the target differs from the new target's
+  // initial map constructor.
+  __ ldr(r0, FieldMemOperand(r2, Map::kConstructorOrBackPointerOffset));
+  __ cmp(r0, r1);
+  __ b(ne, &new_object);
+
+  // Allocate the JSObject on the heap.
+  Label allocate, done_allocate;
+  __ ldrb(r4, FieldMemOperand(r2, Map::kInstanceSizeOffset));
+  __ Allocate(r4, r0, r5, r6, &allocate, SIZE_IN_WORDS);
+  __ bind(&done_allocate);
+
+  // Initialize the JSObject fields.
+  __ str(r2, MemOperand(r0, JSObject::kMapOffset));
+  __ LoadRoot(r3, Heap::kEmptyFixedArrayRootIndex);
+  __ str(r3, MemOperand(r0, JSObject::kPropertiesOffset));
+  __ str(r3, MemOperand(r0, JSObject::kElementsOffset));
+  STATIC_ASSERT(JSObject::kHeaderSize == 3 * kPointerSize);
+  __ add(r1, r0, Operand(JSObject::kHeaderSize));
+
+  // ----------- S t a t e -------------
+  //  -- r0 : result (untagged)
+  //  -- r1 : result fields (untagged)
+  //  -- r5 : result end (untagged)
+  //  -- r2 : initial map
+  //  -- cp : context
+  //  -- lr : return address
+  // -----------------------------------
+
+  // Perform in-object slack tracking if requested.
+  Label slack_tracking;
+  STATIC_ASSERT(Map::kNoSlackTracking == 0);
+  __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
+  __ ldr(r3, FieldMemOperand(r2, Map::kBitField3Offset));
+  __ tst(r3, Operand(Map::ConstructionCounter::kMask));
+  __ b(ne, &slack_tracking);
+  {
+    // Initialize all in-object fields with undefined.
+    __ InitializeFieldsWithFiller(r1, r5, r6);
+
+    // Add the object tag to make the JSObject real.
+    STATIC_ASSERT(kHeapObjectTag == 1);
+    __ add(r0, r0, Operand(kHeapObjectTag));
+    __ Ret();
+  }
+  __ bind(&slack_tracking);
+  {
+    // Decrease generous allocation count.
+    STATIC_ASSERT(Map::ConstructionCounter::kNext == 32);
+    __ sub(r3, r3, Operand(1 << Map::ConstructionCounter::kShift));
+    __ str(r3, FieldMemOperand(r2, Map::kBitField3Offset));
+
+    // Initialize the in-object fields with undefined.
+    __ ldrb(r4, FieldMemOperand(r2, Map::kUnusedPropertyFieldsOffset));
+    __ sub(r4, r5, Operand(r4, LSL, kPointerSizeLog2));
+    __ InitializeFieldsWithFiller(r1, r4, r6);
+
+    // Initialize the remaining (reserved) fields with one pointer filler map.
+    __ LoadRoot(r6, Heap::kOnePointerFillerMapRootIndex);
+    __ InitializeFieldsWithFiller(r1, r5, r6);
+
+    // Add the object tag to make the JSObject real.
+    STATIC_ASSERT(kHeapObjectTag == 1);
+    __ add(r0, r0, Operand(kHeapObjectTag));
+
+    // Check if we can finalize the instance size.
+    STATIC_ASSERT(Map::kSlackTrackingCounterEnd == 1);
+    __ tst(r3, Operand(Map::ConstructionCounter::kMask));
+    __ Ret(ne);
+
+    // Finalize the instance size.
+    {
+      FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+      __ Push(r0, r2);
+      __ CallRuntime(Runtime::kFinalizeInstanceSize);
+      __ Pop(r0);
+    }
+    __ Ret();
+  }
+
+  // Fall back to %AllocateInNewSpace.
+  __ bind(&allocate);
+  {
+    FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+    STATIC_ASSERT(kSmiTag == 0);
+    STATIC_ASSERT(kSmiTagSize == 1);
+    __ mov(r4, Operand(r4, LSL, kPointerSizeLog2 + 1));
+    __ Push(r2, r4);
+    __ CallRuntime(Runtime::kAllocateInNewSpace);
+    __ Pop(r2);
+  }
+  STATIC_ASSERT(kHeapObjectTag == 1);
+  __ sub(r0, r0, Operand(kHeapObjectTag));
+  __ ldrb(r5, FieldMemOperand(r2, Map::kInstanceSizeOffset));
+  __ add(r5, r0, Operand(r5, LSL, kPointerSizeLog2));
+  __ b(&done_allocate);
+
+  // Fall back to %NewObject.
+  __ bind(&new_object);
+  __ Push(r1, r3);
+  __ TailCallRuntime(Runtime::kNewObject);
+}
+
+
 void FastNewRestParameterStub::Generate(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- r1 : function