Inobject slack tracking is done on a per-closure basis instead of per-shared info basis.

src/ia32/builtins-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "v8.h"
 
 #if V8_TARGET_ARCH_IA32
 
 #include "codegen.h"
 #include "deoptimizer.h"
@@ skipping 84 matching lines @@
   CallRuntimePassFunction(masm, Runtime::kHiddenTryInstallOptimizedCode);
   GenerateTailCallToReturnedCode(masm);
 
   __ bind(&ok);
   GenerateTailCallToSharedCode(masm);
 }
 
 
 static void Generate_JSConstructStubHelper(MacroAssembler* masm,
                                            bool is_api_function,
-                                           bool count_constructions,
                                            bool create_memento) {
   // ----------- S t a t e -------------
   //  -- eax: number of arguments
   //  -- edi: constructor function
   //  -- ebx: allocation site or undefined
   // -----------------------------------
 
-  // Should never count constructions for api objects.
-  ASSERT(!is_api_function || !count_constructions);
-
   // Should never create mementos for api functions.
   ASSERT(!is_api_function || !create_memento);
 
-  // Should never create mementos before slack tracking is finished.
-  ASSERT(!count_constructions || !create_memento);
-
   // Enter a construct frame.
   {
     FrameScope scope(masm, StackFrame::CONSTRUCT);
 
     if (create_memento) {
       __ AssertUndefinedOrAllocationSite(ebx);
       __ push(ebx);
     }
 
     // Store a smi-tagged arguments count on the stack.
@@ skipping 25 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.
       // edi: constructor
       // eax: initial map
       __ CmpInstanceType(eax, JS_FUNCTION_TYPE);
       __ j(equal, &rt_call);
 
-      if (count_constructions) {
+      if (!is_api_function) {
         Label allocate;
+        // The code below relies on these assumptions.
+        STATIC_ASSERT(JSFunction::kNoSlackTracking == 0);
+        STATIC_ASSERT(Map::ConstructionCount::kShift +
+                      Map::ConstructionCount::kSize == 32);
+        // Check if slack tracking is enabled.
+        __ mov(esi, FieldOperand(eax, Map::kBitField3Offset));
+        __ shr(esi, Map::ConstructionCount::kShift);
+        __ j(zero, &allocate);  // JSFunction::kNoSlackTracking
         // Decrease generous allocation count.
-        __ mov(ecx, FieldOperand(edi, JSFunction::kSharedFunctionInfoOffset));
-        __ dec_b(FieldOperand(ecx,
-                              SharedFunctionInfo::kConstructionCountOffset));
-        __ j(not_zero, &allocate);
+        __ sub(FieldOperand(eax, Map::kBitField3Offset),
+               Immediate(1 << Map::ConstructionCount::kShift));
+
+        __ cmp(esi, JSFunction::kFinishSlackTracking);
+        __ j(not_equal, &allocate);
 
         __ push(eax);
         __ push(edi);
 
         __ push(edi);  // constructor
-        // The call will replace the stub, so the countdown is only done once.
         __ CallRuntime(Runtime::kHiddenFinalizeInstanceSize, 1);
 
         __ pop(edi);
         __ pop(eax);
+        __ xor_(esi, esi);  // JSFunction::kNoSlackTracking
 
         __ bind(&allocate);
       }
 
       // Now allocate the JSObject on the heap.
       // edi: constructor
       // eax: initial map
       __ movzx_b(edi, FieldOperand(eax, Map::kInstanceSizeOffset));
       __ shl(edi, kPointerSizeLog2);
       if (create_memento) {
         __ add(edi, Immediate(AllocationMemento::kSize));
       }
 
       __ Allocate(edi, ebx, edi, no_reg, &rt_call, NO_ALLOCATION_FLAGS);
 
       Factory* factory = masm->isolate()->factory();
 
       // Allocated the JSObject, now initialize the fields.
       // eax: initial map
       // ebx: JSObject
       // edi: start of next object (including memento if create_memento)
       __ mov(Operand(ebx, JSObject::kMapOffset), eax);
       __ mov(ecx, factory->empty_fixed_array());
       __ mov(Operand(ebx, JSObject::kPropertiesOffset), ecx);
       __ mov(Operand(ebx, JSObject::kElementsOffset), ecx);
       // Set extra fields in the newly allocated object.
       // eax: initial map
       // ebx: JSObject
       // edi: start of next object (including memento if create_memento)
+      // esi: slack tracking counter (non-API function case)
+      __ mov(edx, factory->undefined_value());
       __ lea(ecx, Operand(ebx, JSObject::kHeaderSize));
-      __ mov(edx, factory->undefined_value());
-      if (count_constructions) {
+      if (!is_api_function) {
+        Label no_inobject_slack_tracking;
+
+        // Check if slack tracking is enabled.
+        __ cmp(esi, JSFunction::kNoSlackTracking);
+        __ j(equal, &no_inobject_slack_tracking);
+
+        // Allocate object with a slack.
         __ movzx_b(esi,
                    FieldOperand(eax, Map::kPreAllocatedPropertyFieldsOffset));
         __ lea(esi,
                Operand(ebx, esi, times_pointer_size, JSObject::kHeaderSize));
         // esi: offset of first field after pre-allocated fields
         if (FLAG_debug_code) {
           __ cmp(esi, edi);
           __ Assert(less_equal,
                     kUnexpectedNumberOfPreAllocatedPropertyFields);
         }
         __ InitializeFieldsWithFiller(ecx, esi, edx);
         __ mov(edx, factory->one_pointer_filler_map());
-        __ InitializeFieldsWithFiller(ecx, edi, edx);
-      } else if (create_memento) {
+        // Fill the remaining fields with one pointer filler map.
+
+        __ bind(&no_inobject_slack_tracking);
+      }
+
+      if (create_memento) {
         __ lea(esi, Operand(edi, -AllocationMemento::kSize));
         __ InitializeFieldsWithFiller(ecx, esi, edx);
 
         // Fill in memento fields if necessary.
         // esi: points to the allocated but uninitialized memento.
-        Handle<Map> allocation_memento_map = factory->allocation_memento_map();
         __ mov(Operand(esi, AllocationMemento::kMapOffset),
-               allocation_memento_map);
+               factory->allocation_memento_map());
         // Get the cell or undefined.
         __ mov(edx, Operand(esp, kPointerSize*2));
         __ mov(Operand(esi, AllocationMemento::kAllocationSiteOffset),
                edx);
       } else {
         __ InitializeFieldsWithFiller(ecx, edi, edx);
       }
 
       // Add the object tag to make the JSObject real, so that we can continue
       // and jump into the continuation code at any time from now on. Any
@@ skipping 158 matching lines @@
       Handle<Code> code =
           masm->isolate()->builtins()->HandleApiCallConstruct();
       __ call(code, RelocInfo::CODE_TARGET);
     } else {
       ParameterCount actual(eax);
       __ InvokeFunction(edi, actual, CALL_FUNCTION,
                         NullCallWrapper());
     }
 
     // Store offset of return address for deoptimizer.
-    if (!is_api_function && !count_constructions) {
+    if (!is_api_function) {
       masm->isolate()->heap()->SetConstructStubDeoptPCOffset(masm->pc_offset());
     }
 
     // Restore context from the frame.
     __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
 
     // If the result is an object (in the ECMA sense), we should get rid
     // of the receiver and use the result; see ECMA-262 section 13.2.2-7
     // on page 74.
     Label use_receiver, exit;
@@ skipping 21 matching lines @@
   // Remove caller arguments from the stack and return.
   STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ pop(ecx);
   __ lea(esp, Operand(esp, ebx, times_2, 1 * kPointerSize));  // 1 ~ receiver
   __ push(ecx);
   __ IncrementCounter(masm->isolate()->counters()->constructed_objects(), 1);
   __ ret(0);
 }
 
 
-void Builtins::Generate_JSConstructStubCountdown(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, false, true, false);
-}
-
-
 void Builtins::Generate_JSConstructStubGeneric(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, false, false, FLAG_pretenuring_call_new);
+  Generate_JSConstructStubHelper(masm, false, FLAG_pretenuring_call_new);
 }
 
 
 void Builtins::Generate_JSConstructStubApi(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, true, false, false);
+  Generate_JSConstructStubHelper(masm, true, false);
 }
 
 
 static void Generate_JSEntryTrampolineHelper(MacroAssembler* masm,
                                              bool is_construct) {
   ProfileEntryHookStub::MaybeCallEntryHook(masm);
 
   // Clear the context before we push it when entering the internal frame.
   __ Move(esi, Immediate(0));
 
@@ skipping 954 matching lines @@
 
   __ bind(&ok);
   __ ret(0);
 }
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32