Pretenure call new support.

src/x64/builtins-x64.cc

 // Copyright 2012 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 106 matching lines @@
   CallRuntimePassFunction(masm, Runtime::kTryInstallOptimizedCode);
   GenerateTailCallToReturnedCode(masm);
 
   __ bind(&ok);
   GenerateTailCallToSharedCode(masm);
 }
 
 
 static void Generate_JSConstructStubHelper(MacroAssembler* masm,
                                            bool is_api_function,
-                                           bool count_constructions) {
+                                           bool count_constructions,
+                                           bool create_memento) {
   // ----------- S t a t e -------------
   //  -- rax: number of arguments
   //  -- rdi: constructor function
+  //  -- rbx: allocation site or undefined
   // -----------------------------------
 
   // Should never count constructions for api objects.
-  ASSERT(!is_api_function || !count_constructions);
+  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(rbx);
+      __ push(rbx);
+    }
+
     // Store a smi-tagged arguments count on the stack.
     __ Integer32ToSmi(rax, rax);
     __ push(rax);
 
     // Push the function to invoke on the stack.
     __ push(rdi);
 
     // Try to allocate the object without transitioning into C code. If any of
     // the preconditions is not met, the code bails out to the runtime call.
     Label rt_call, allocated;
@@ skipping 45 matching lines @@
 
         __ pop(rdi);
         __ pop(rax);
 
         __ bind(&allocate);
       }
 
       // Now allocate the JSObject on the heap.
       __ movzxbq(rdi, FieldOperand(rax, Map::kInstanceSizeOffset));
       __ shl(rdi, Immediate(kPointerSizeLog2));
+      if (create_memento) {
+        __ addq(rdi, Immediate(AllocationMemento::kSize));
+      }
       // rdi: size of new object
       __ Allocate(rdi,
                   rbx,
                   rdi,
                   no_reg,
                   &rt_call,
                   NO_ALLOCATION_FLAGS);
+      Factory* factory = masm->isolate()->factory();
       // Allocated the JSObject, now initialize the fields.
       // rax: initial map
       // rbx: JSObject (not HeapObject tagged - the actual address).
-      // rdi: start of next object
+      // rdi: start of next object (including memento if create_memento)
       __ movp(Operand(rbx, JSObject::kMapOffset), rax);
       __ LoadRoot(rcx, Heap::kEmptyFixedArrayRootIndex);
       __ movp(Operand(rbx, JSObject::kPropertiesOffset), rcx);
       __ movp(Operand(rbx, JSObject::kElementsOffset), rcx);
       // Set extra fields in the newly allocated object.
       // rax: initial map
       // rbx: JSObject
-      // rdi: start of next object
+      // rdi: start of next object (including memento if create_memento)
       __ lea(rcx, Operand(rbx, JSObject::kHeaderSize));
       __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
       if (count_constructions) {
         __ movzxbq(rsi,
                    FieldOperand(rax, Map::kPreAllocatedPropertyFieldsOffset));
         __ lea(rsi,
                Operand(rbx, rsi, times_pointer_size, JSObject::kHeaderSize));
         // rsi: offset of first field after pre-allocated fields
         if (FLAG_debug_code) {
           __ cmpq(rsi, rdi);
           __ Assert(less_equal,
                     kUnexpectedNumberOfPreAllocatedPropertyFields);
         }
         __ InitializeFieldsWithFiller(rcx, rsi, rdx);
         __ LoadRoot(rdx, Heap::kOnePointerFillerMapRootIndex);
+        __ InitializeFieldsWithFiller(rcx, rdi, rdx);
+      } else if (create_memento) {
+        __ lea(rsi, Operand(rdi, -AllocationMemento::kSize));
+        __ InitializeFieldsWithFiller(rcx, rsi, rdx);
+
+        // Fill in memento fields if necessary.
+        // rsi: points to the allocated but uninitialized memento.
+        Handle<Map> allocation_memento_map = factory->allocation_memento_map();
+        __ Move(Operand(rsi, AllocationMemento::kMapOffset),
+                allocation_memento_map);
+        // Get the cell or undefined.
+        __ movp(rdx, Operand(rsp, kPointerSize*2));
+        __ movp(Operand(rsi, AllocationMemento::kAllocationSiteOffset),
+                rdx);
+      } else {
+        __ InitializeFieldsWithFiller(rcx, rdi, rdx);
       }

[Hannes Payer (out of office), 2014/02/18 16:24:26]

__ InitializeFieldsWithFiller(rcx, rdi, rdx); outside the if/else?

[mvstanton, 2014/02/19 08:40:26]

It's awkward to do it because in the create_memento case
it's called with the arg RSI instead of RDI. (ia32 looks similar).

In general this "filling object fields" code was tricky enough that I finally
opted for a single logical structure to lay out the code at the expense of some
duplication/near-duplication.

-      __ InitializeFieldsWithFiller(rcx, rdi, rdx);
 
       // 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.
       // rax: initial map
       // rbx: JSObject
       // rdi: start of next object
       __ or_(rbx, Immediate(kHeapObjectTag));
 
@@ skipping 71 matching lines @@
       // example, the map's unused properties potentially do not match the
       // allocated objects unused properties.
       // rbx: JSObject (previous new top)
       __ bind(&undo_allocation);
       __ UndoAllocationInNewSpace(rbx);
     }
 
     // Allocate the new receiver object using the runtime call.
     // rdi: function (constructor)
     __ bind(&rt_call);
+    int offset = 0;
+    if (create_memento) {
+      // Get the cell or allocation site.
+      __ movp(rdi, Operand(rsp, kPointerSize*2));
+      __ push(rdi);
+      offset = kPointerSize;
+    }
+
     // Must restore rdi (constructor) before calling runtime.
-    __ movp(rdi, Operand(rsp, 0));
+    __ movp(rdi, Operand(rsp, offset));
     __ push(rdi);
-    __ CallRuntime(Runtime::kNewObject, 1);
+    if (create_memento) {
+      __ CallRuntime(Runtime::kNewObjectWithAllocationSite, 2);
+    } else {
+      __ CallRuntime(Runtime::kNewObject, 1);
+    }
     __ movp(rbx, rax);  // store result in rbx
 
+    // If we ended up using the runtime, and we want a memento, then the
+    // runtime call made it for us, and we shouldn't do create count
+    // increment.
+    Label count_incremented;
+    if (create_memento) {
+      __ jmp(&count_incremented);
+    }
+
     // New object allocated.
     // rbx: newly allocated object
     __ bind(&allocated);
+
+    if (create_memento) {
+      __ movp(rcx, Operand(rsp, kPointerSize*2));
+      __ Cmp(rcx, masm->isolate()->factory()->undefined_value());
+      __ j(equal, &count_incremented);
+      // rcx is an AllocationSite. We are creating a memento from it, so we
+      // need to increment the memento create count.
+      __ SmiAddConstant(
+          FieldOperand(rcx, AllocationSite::kPretenureCreateCountOffset),
+          Smi::FromInt(1));
+      __ bind(&count_incremented);
+    }

[Hannes Payer (out of office), 2014/02/18 16:24:26]

__ bind(&count_incremented); outside of if?

[mvstanton, 2014/02/19 08:40:26]

I thought about that a lot, and decided to put it inside because the only
"jumper" to that target is in a "if (create_memento)", and this means that any
other unsanctioned jumper to that address would get a fast crash at compile
time. By sticking it inside that block, someone without create_memento == true
cannot possibly jump to it and succeed in compiling this code. We compile it at
snapshot time so it's a fast/useful error.

I saw this pattern in other places...I agree it's weird but it's safer.

+
     // Retrieve the function from the stack.
     __ pop(rdi);
 
     // Retrieve smi-tagged arguments count from the stack.
     __ movp(rax, Operand(rsp, 0));
     __ SmiToInteger32(rax, rax);
 
     // Push the allocated receiver to the stack. We need two copies
     // because we may have to return the original one and the calling
     // conventions dictate that the called function pops the receiver.
@@ skipping 62 matching lines @@
   SmiIndex index = masm->SmiToIndex(rbx, rbx, kPointerSizeLog2);
   __ lea(rsp, Operand(rsp, index.reg, index.scale, 1 * kPointerSize));
   __ PushReturnAddressFrom(rcx);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->constructed_objects(), 1);
   __ ret(0);
 }
 
 
 void Builtins::Generate_JSConstructStubCountdown(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, false, true);
+  Generate_JSConstructStubHelper(masm, false, true, false);
 }
 
 
 void Builtins::Generate_JSConstructStubGeneric(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, false, false);
+  Generate_JSConstructStubHelper(masm, false, false, true);
 }
 
 
 void Builtins::Generate_JSConstructStubApi(MacroAssembler* masm) {
-  Generate_JSConstructStubHelper(masm, true, false);
+  Generate_JSConstructStubHelper(masm, true, false, false);
 }
 
 
 static void Generate_JSEntryTrampolineHelper(MacroAssembler* masm,
                                              bool is_construct) {
   ProfileEntryHookStub::MaybeCallEntryHook(masm);
 
   // Expects five C++ function parameters.
   // - Address entry (ignored)
   // - JSFunction* function (
@@ skipping 990 matching lines @@
   __ bind(&ok);
   __ ret(0);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64