Fix memento initialization when constructing from new call

src/ia32/builtins-ia32.cc

Index: src/ia32/builtins-ia32.cc
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index 5cbecc22bafd2aa8099bb8ab2a4e08da8a056bdf..6a80ddd23d68b8714f316b110b638981626457de 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -117,10 +117,9 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
   {
     FrameScope scope(masm, StackFrame::CONSTRUCT);
 
-    if (create_memento) {
-      __ AssertUndefinedOrAllocationSite(ebx);
-      __ push(ebx);
-    }
+    // Always push a potential allocation site to preserve a fixed frame size.

[Michael Starzinger, 2015/07/16 14:08:28]

nit: Ideally this behavior will become the default once we turn the flag on. So
I think it might even be fine to just drop this comment and move the push into
the block at line 124 without specifically mentioning the allocation site.
Applies to all architectures.

[Michael Lippautz, 2015/07/16 14:15:35]

Done.

+    __ AssertUndefinedOrAllocationSite(ebx);
+    __ push(ebx);
 
     // Preserve the incoming parameters on the stack.
     __ SmiTag(eax);
@@ -254,7 +253,8 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
         __ mov(Operand(esi, AllocationMemento::kMapOffset),
                factory->allocation_memento_map());
         // Get the cell or undefined.
-        __ mov(edx, Operand(esp, kPointerSize*2));
+        __ mov(edx, Operand(esp, 3 * kPointerSize));

[Michael Starzinger, 2015/07/16 14:08:28]

Nice catch!

[Michael Lippautz, 2015/07/16 14:15:35]

Acknowledged.

+        __ AssertUndefinedOrAllocationSite(edx);
         __ mov(Operand(esi, AllocationMemento::kAllocationSiteOffset),
                edx);
       } else {
@@ -422,12 +422,13 @@ void Builtins::Generate_JSConstructStubForDerived(MacroAssembler* masm) {
   //  -- edx: original constructor
   // -----------------------------------
 
-  // TODO(dslomov): support pretenuring
-  CHECK(!FLAG_pretenuring_call_new);
-
   {
     FrameScope frame_scope(masm, StackFrame::CONSTRUCT);
 
+    // Always push a potential allocation site to preserve a fixed frame size.

[Michael Starzinger, 2015/07/16 14:08:28]

Likewise.

[Michael Lippautz, 2015/07/16 14:15:35]

Done.

+    __ AssertUndefinedOrAllocationSite(ebx);
+    __ push(ebx);
+
     // Preserve actual arguments count.
     __ SmiTag(eax);
     __ push(eax);