Support double allocations when folding allocation.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 475c405d0d67823ca5c7c2279f054b78f683123f..1c7df8e5e4553a45b608217f586fd554c9d30b6c 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3910,6 +3910,11 @@ void LCodeGen::DoCallRuntime(LCallRuntime* instr) {
 void LCodeGen::DoInnerAllocatedObject(LInnerAllocatedObject* instr) {
   Register result = ToRegister(instr->result());
   Register base = ToRegister(instr->base_object());
+  if (instr->hydrogen()->MustAllocateDoubleAligned()) {
+    ASSERT(kPointerAlignment == kDoubleAlignment);
+    __ testq(result, Immediate(kDoubleAlignmentMask));
+    __ Check(zero, "Allocation is not double aligned");
+  }
   __ lea(result, Operand(base, instr->offset()));
 }