Dynamically determine optimal instance size....

src/x64/builtins-x64.cc

 // Copyright 2009 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 895 matching lines @@
   __ bind(&non_function_call);
   // Set expected number of arguments to zero (not changing rax).
   __ movq(rbx, Immediate(0));
   __ GetBuiltinEntry(rdx, Builtins::CALL_NON_FUNCTION_AS_CONSTRUCTOR);
   __ Jump(Handle<Code>(builtin(ArgumentsAdaptorTrampoline)),
           RelocInfo::CODE_TARGET);
 }
 
 
 static void Generate_JSConstructStubHelper(MacroAssembler* masm,
-                                           bool is_api_function) {
+                                           bool is_api_function,
+                                           bool count_constructions) {
+  // Should never count constructions for api objects.
+  ASSERT(!is_api_function || !count_constructions);
+
     // Enter a construct frame.
   __ EnterConstructFrame();
 
   // Store a smi-tagged arguments count on the stack.
   __ Integer32ToSmi(rax, rax);
   __ push(rax);
 
   // Push the function to invoke on the stack.
   __ push(rdi);
 
@@ skipping 24 matching lines @@
     __ j(not_equal, &rt_call);
 
     // Check that the constructor is not constructing a JSFunction (see comments
     // in Runtime_NewObject in runtime.cc). In which case the initial map's
     // instance type would be JS_FUNCTION_TYPE.
     // rdi: constructor
     // rax: initial map
     __ CmpInstanceType(rax, JS_FUNCTION_TYPE);
     __ j(equal, &rt_call);
 
+    if (count_constructions) {
+      Label allocate;
+      // Decrease generous allocation count.
+      __ movq(rcx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+      __ decb(FieldOperand(rcx, SharedFunctionInfo::kConstructionCountOffset));
+      __ j(not_zero, &allocate);
+
+      __ push(rax);
+      __ push(rdi);
+
+      __ push(rdi);  // constructor
+      // The call will replace the stub, so the countdown is only done once.
+      __ CallRuntime(Runtime::kFinalizeInstanceSize, 1);
+
+      __ pop(rdi);
+      __ pop(rax);
+
+      __ bind(&allocate);
+    }
+
     // Now allocate the JSObject on the heap.
     __ movzxbq(rdi, FieldOperand(rax, Map::kInstanceSizeOffset));
     __ shl(rdi, Immediate(kPointerSizeLog2));
     // rdi: size of new object
     __ AllocateInNewSpace(rdi,
                           rbx,
                           rdi,
                           no_reg,
                           &rt_call,
                           NO_ALLOCATION_FLAGS);
     // Allocated the JSObject, now initialize the fields.
     // rax: initial map
     // rbx: JSObject (not HeapObject tagged - the actual address).
     // rdi: start of next object
     __ movq(Operand(rbx, JSObject::kMapOffset), rax);
     __ LoadRoot(rcx, Heap::kEmptyFixedArrayRootIndex);
     __ movq(Operand(rbx, JSObject::kPropertiesOffset), rcx);
     __ movq(Operand(rbx, JSObject::kElementsOffset), rcx);
     // Set extra fields in the newly allocated object.
     // rax: initial map
     // rbx: JSObject
     // rdi: start of next object
     { Label loop, entry;
-      __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
+      // To allow for truncation.
+      if (count_constructions) {
+        __ LoadRoot(rdx, Heap::kOnePointerFillerMapRootIndex);
+      } else {
+        __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
+      }
       __ lea(rcx, Operand(rbx, JSObject::kHeaderSize));
       __ jmp(&entry);
       __ bind(&loop);
       __ movq(Operand(rcx, 0), rdx);
       __ addq(rcx, Immediate(kPointerSize));
       __ bind(&entry);
       __ cmpq(rcx, rdi);
       __ j(less, &loop);
     }
 
@@ skipping 162 matching lines @@
   // Remove caller arguments from the stack and return.
   __ pop(rcx);
   SmiIndex index = masm->SmiToIndex(rbx, rbx, kPointerSizeLog2);
   __ lea(rsp, Operand(rsp, index.reg, index.scale, 1 * kPointerSize));
   __ push(rcx);
   __ IncrementCounter(&Counters::constructed_objects, 1);
   __ ret(0);
 }
 
 
+void Builtins::Generate_JSConstructStubCountdown(MacroAssembler* masm) {
+  Generate_JSConstructStubHelper(masm, false, true);
+}
+
+
 void Builtins::Generate_JSConstructStubGeneric(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, false);
+  Generate_JSConstructStubHelper(masm, false, false);
 }
 
 
 void Builtins::Generate_JSConstructStubApi(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, true);
+  Generate_JSConstructStubHelper(masm, true, false);
 }
 
 
 static void Generate_JSEntryTrampolineHelper(MacroAssembler* masm,
                                              bool is_construct) {
   // Expects five C++ function parameters.
   // - Address entry (ignored)
   // - JSFunction* function (
   // - Object* receiver
   // - int argc
@@ skipping 125 matching lines @@
   __ LeaveInternalFrame();
 
   // Do a tail-call of the compiled function.
   __ lea(rcx, FieldOperand(rax, Code::kHeaderSize));
   __ jmp(rcx);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64