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

src/arm/builtins-arm.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_ARM
 
 #include "codegen.h"
 #include "debug.h"
@@ skipping 295 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 -------------
   //  -- r0     : number of arguments
   //  -- r1     : constructor function
   //  -- r2     : allocation site or undefined
   //  -- lr     : return address
   //  -- sp[...]: constructor arguments
   // -----------------------------------
 
-  // 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);
-
   Isolate* isolate = masm->isolate();
 
   // Enter a construct frame.
   {
     FrameAndConstantPoolScope scope(masm, StackFrame::CONSTRUCT);
 
     if (create_memento) {
       __ AssertUndefinedOrAllocationSite(r2, r3);
       __ push(r2);
     }
@@ skipping 23 matching lines @@
       __ b(ne, &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.
       // r1: constructor function
       // r2: initial map
       __ CompareInstanceType(r2, r3, JS_FUNCTION_TYPE);
       __ b(eq, &rt_call);
 
-      if (count_constructions) {
+      if (!is_api_function) {
         Label allocate;
+        MemOperand bit_field3 = FieldMemOperand(r2, Map::kBitField3Offset);
+        // Check if slack tracking is enabled.
+        __ ldr(r4, bit_field3);
+        __ DecodeField<Map::ConstructionCount>(r3, r4);
+        __ cmp(r3, Operand(static_cast<int32_t>(JSFunction::kNoSlackTracking)));
+        __ b(eq, &allocate);
         // Decrease generous allocation count.
-        __ ldr(r3, FieldMemOperand(r1, JSFunction::kSharedFunctionInfoOffset));
-        MemOperand constructor_count =
-            FieldMemOperand(r3, SharedFunctionInfo::kConstructionCountOffset);
-        __ ldrb(r4, constructor_count);
-        __ sub(r4, r4, Operand(1), SetCC);
-        __ strb(r4, constructor_count);
+        __ sub(r4, r4, Operand(1 << Map::ConstructionCount::kShift));
+        __ str(r4, bit_field3);
+        __ cmp(r3,
+               Operand(static_cast<int32_t>(JSFunction::kFinishSlackTracking)));
         __ b(ne, &allocate);
 
         __ push(r1);
 
         __ Push(r2, r1);  // r1 = constructor
-        // The call will replace the stub, so the countdown is only done once.
         __ CallRuntime(Runtime::kHiddenFinalizeInstanceSize, 1);
 
         __ pop(r2);
         __ pop(r1);
 
         __ bind(&allocate);
       }
 
       // Now allocate the JSObject on the heap.
       // r1: constructor function
@@ skipping 21 matching lines @@
       __ str(r6, MemOperand(r5, kPointerSize, PostIndex));
 
       // Fill all the in-object properties with the appropriate filler.
       // r1: constructor function
       // r2: initial map
       // r3: object size (in words, including memento if create_memento)
       // r4: JSObject (not tagged)
       // r5: First in-object property of JSObject (not tagged)
       ASSERT_EQ(3 * kPointerSize, JSObject::kHeaderSize);
 
-      if (count_constructions) {
+      if (is_api_function) {
+        __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
+        __ add(r0, r4, Operand(r3, LSL, kPointerSizeLog2));  // End of object.
+        __ InitializeFieldsWithFiller(r5, r0, r6);
+      } else {
+        Label no_inobject_slack_tracking, done_field_initialization;
+
+        // Check if slack tracking is enabled.
+        __ ldr(r6, FieldMemOperand(r2, Map::kBitField3Offset));
+        __ DecodeField<Map::ConstructionCount>(r6);
+        __ cmp(r6, Operand(static_cast<int32_t>(JSFunction::kNoSlackTracking)));
+        __ b(eq, &no_inobject_slack_tracking);
+
+        // Allocate object with a slack.
         __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
         __ ldr(r0, FieldMemOperand(r2, Map::kInstanceSizesOffset));
         __ Ubfx(r0, r0, Map::kPreAllocatedPropertyFieldsByte * kBitsPerByte,
                 kBitsPerByte);
         __ add(r0, r5, Operand(r0, LSL, kPointerSizeLog2));
         // r0: offset of first field after pre-allocated fields
         if (FLAG_debug_code) {
           __ add(ip, r4, Operand(r3, LSL, kPointerSizeLog2));  // End of object.
           __ cmp(r0, ip);
           __ Assert(le, kUnexpectedNumberOfPreAllocatedPropertyFields);
         }
         __ InitializeFieldsWithFiller(r5, r0, r6);
         // To allow for truncation.
         __ LoadRoot(r6, Heap::kOnePointerFillerMapRootIndex);
         __ add(r0, r4, Operand(r3, LSL, kPointerSizeLog2));  // End of object.
         __ InitializeFieldsWithFiller(r5, r0, r6);
-      } else if (create_memento) {
-        __ sub(r6, r3, Operand(AllocationMemento::kSize / kPointerSize));
-        __ add(r0, r4, Operand(r6, LSL, kPointerSizeLog2));  // End of object.
-        __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
-        __ InitializeFieldsWithFiller(r5, r0, r6);
+        __ b(&done_field_initialization);
 
-        // Fill in memento fields.
-        // r5: points to the allocated but uninitialized memento.
-        __ LoadRoot(r6, Heap::kAllocationMementoMapRootIndex);
-        ASSERT_EQ(0 * kPointerSize, AllocationMemento::kMapOffset);
-        __ str(r6, MemOperand(r5, kPointerSize, PostIndex));
-        // Load the AllocationSite
-        __ ldr(r6, MemOperand(sp, 2 * kPointerSize));
-        ASSERT_EQ(1 * kPointerSize, AllocationMemento::kAllocationSiteOffset);
-        __ str(r6, MemOperand(r5, kPointerSize, PostIndex));
-      } else {
-        __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
-        __ add(r0, r4, Operand(r3, LSL, kPointerSizeLog2));  // End of object.
-        __ InitializeFieldsWithFiller(r5, r0, r6);
+        __ bind(&no_inobject_slack_tracking);
+
+        if (create_memento) {
+          __ sub(r6, r3, Operand(AllocationMemento::kSize / kPointerSize));
+          __ add(r0, r4, Operand(r6, LSL, kPointerSizeLog2));  // End of object.
+          __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
+          __ InitializeFieldsWithFiller(r5, r0, r6);
+
+          // Fill in memento fields.
+          // r5: points to the allocated but uninitialized memento.
+          __ LoadRoot(r6, Heap::kAllocationMementoMapRootIndex);
+          ASSERT_EQ(0 * kPointerSize, AllocationMemento::kMapOffset);
+          __ str(r6, MemOperand(r5, kPointerSize, PostIndex));
+          // Load the AllocationSite
+          __ ldr(r6, MemOperand(sp, 2 * kPointerSize));
+          ASSERT_EQ(1 * kPointerSize, AllocationMemento::kAllocationSiteOffset);
+          __ str(r6, MemOperand(r5, kPointerSize, PostIndex));
+        } else {
+          __ LoadRoot(r6, Heap::kUndefinedValueRootIndex);
+          __ add(r0, r4, Operand(r3, LSL, kPointerSizeLog2));  // End of object.
+          __ InitializeFieldsWithFiller(r5, r0, r6);
+        }
+        __ bind(&done_field_initialization);
       }
 
       // 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
       // failures need to undo the allocation, so that the heap is in a
       // consistent state and verifiable.
       __ add(r4, r4, Operand(kHeapObjectTag));
 
       // Check if a non-empty properties array is needed. Continue with
       // allocated object if not fall through to runtime call if it is.
@@ skipping 168 matching lines @@
       __ ldr(cp, FieldMemOperand(r1, JSFunction::kContextOffset));
       Handle<Code> code =
           masm->isolate()->builtins()->HandleApiCallConstruct();
       __ Call(code, RelocInfo::CODE_TARGET);
     } else {
       ParameterCount actual(r0);
       __ InvokeFunction(r1, 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.
     // r0: result
     // sp[0]: receiver
     // sp[1]: constructor function
     // sp[2]: number of arguments (smi-tagged)
     __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
 
@@ skipping 31 matching lines @@
     // Leave construct frame.
   }
 
   __ add(sp, sp, Operand(r1, LSL, kPointerSizeLog2 - 1));
   __ add(sp, sp, Operand(kPointerSize));
   __ IncrementCounter(isolate->counters()->constructed_objects(), 1, r1, r2);
   __ Jump(lr);
 }
 
 
-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) {
   // Called from Generate_JS_Entry
   // r0: code entry
   // r1: function
   // r2: receiver
   // r3: argc
@@ skipping 819 matching lines @@
     __ bkpt(0);
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM