DBC: Enables unboxed doubles

runtime/vm/deopt_instructions.cc

Index: runtime/vm/deopt_instructions.cc
diff --git a/runtime/vm/deopt_instructions.cc b/runtime/vm/deopt_instructions.cc
index f31a8976590d103ef9e61168423dd7086b855128..06e2fee8665394f58020477a065a19cde2d98e63 100644
--- a/runtime/vm/deopt_instructions.cc
+++ b/runtime/vm/deopt_instructions.cc
@@ -1122,8 +1122,14 @@ void DeoptInfoBuilder::AddCopy(Value* value,
             ToCpuRegisterSource(source_loc));
         break;
       case kUnboxedDouble:
+#if !defined(TARGET_ARCH_DBC)
         deopt_instr = new(zone()) DeoptDoubleInstr(
             ToFpuRegisterSource(source_loc, Location::kDoubleStackSlot));
+#else
+        // DBC stores unboxed doubles in regular registers (i.e. stack slots).
+        deopt_instr = new(zone()) DeoptWordInstr(

[Vyacheslav Egorov (Google), 2016/07/14 16:26:24]

This seems incorrect. DeoptDoubleInstr takes care of materializing Double object
on deoptimization. DeoptWorkInstr would not do it. It just copies things as is.

Please write some microtest that deoptimizes with unboxed double to verify that
it is materialized correctly.

[zra, 2016/07/14 21:12:10]

Done.

+            ToCpuRegisterSource(source_loc));
+#endif
         break;
       case kUnboxedFloat32x4:
         deopt_instr = new(zone()) DeoptFloat32x4Instr(