DBC: Eager deoptimization and CheckSmi instruction.

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 1839f7fae8a14eb760f594f2148744adb99bc4f8..09ee4e6dbcdf06b8abc3c182a07fcb5017c75bd9 100644
--- a/runtime/vm/deopt_instructions.cc
+++ b/runtime/vm/deopt_instructions.cc
@@ -67,13 +67,17 @@ DeoptContext::DeoptContext(const StackFrame* frame,
   // return-address. This section is copied as well, so that its contained
   // values can be updated before returning to the deoptimized function.
   // Note: on DBC stack grows upwards unlike on all other architectures.
+  const intptr_t frame_size =
+#if defined(TARGET_ARCH_DBC)
+      (static_cast<intptr_t>(frame->sp()) -
+       static_cast<intptr_t>(frame->fp())) / kWordSize;
+#else
+      (static_cast<intptr_t>(frame->fp()) -
+       static_cast<intptr_t>(frame->sp())) / kWordSize;
+#endif
   source_frame_size_ =
       + kDartFrameFixedSize  // For saved values below sp.
-#if !defined(TARGET_ARCH_DBC)
-      + ((frame->fp() - frame->sp()) / kWordSize)  // For frame size incl. sp.
-#else
-      + ((frame->sp() - frame->fp()) / kWordSize)  // For frame size incl. sp.

[zra, 2016/06/07 22:31:28]

For some reason sp() is < fp() ? Moved around to at least avoid getting
something totally wrong from unsigned arithmetic cast to signed.

[Vyacheslav Egorov (Google), 2016/06/08 11:58:53]

If SP is less then FP on DBC then this is bug somewhere else.

[zra, 2016/06/08 17:46:30]

Added ASSERT.

-#endif  // !defined(TARGET_ARCH_DBC)
+      + frame_size  // For frame size incl. sp.
       + 1  // For fp.
       + kParamEndSlotFromFp  // For saved values above fp.
       + num_args_;  // For arguments.