Support double allocations when folding allocation.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 16476a9c5a95c2b9a1bcca90e388255d7d25438b..68c8139943dd0c37894e3a2bb4452d65d9b54831 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -3210,12 +3210,10 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
   HValue* dominator_size = dominator_allocate_instr->size();
   HValue* current_size = size();
   // We can just fold allocations that are guaranteed in new space.
-  // TODO(hpayer): Support double aligned allocations.
   // TODO(hpayer): Add support for non-constant allocation in dominator.
-  if (!GuaranteedInNewSpace() || MustAllocateDoubleAligned() ||
+  if (!GuaranteedInNewSpace() ||
       !current_size->IsInteger32Constant() ||
       !dominator_allocate_instr->GuaranteedInNewSpace() ||
-      dominator_allocate_instr->MustAllocateDoubleAligned() ||
       !dominator_size->IsInteger32Constant()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s)\n",
@@ -3229,7 +3227,13 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
       HConstant::cast(dominator_size)->GetInteger32Constant();
   int32_t current_size_constant =
       HConstant::cast(current_size)->GetInteger32Constant();
-  int32_t new_dominator_size = dominator_size_constant + current_size_constant;
+  int32_t new_dominator_size =
+      dominator_size_constant + current_size_constant;
+  bool double_alignment = MustAllocateDoubleAligned() &&
+      kPointerAlignment != kDoubleAlignment;
+
+  if (double_alignment) new_dominator_size += kDoubleSize / 2;
+
   if (new_dominator_size > Page::kMaxNonCodeHeapObjectSize) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s) due to size: %d\n",
@@ -3255,7 +3259,8 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
   HInstruction* dominated_allocate_instr =
       new(zone) HInnerAllocatedObject(dominator_allocate_instr,
                                       dominator_size_constant,
-                                      type());
+                                      type(),
+                                      double_alignment);
   dominated_allocate_instr->InsertBefore(this);
   DeleteAndReplaceWith(dominated_allocate_instr);
   if (FLAG_trace_allocation_folding) {