Re-landing of "replace TrySync with Metadata".

runtime/vm/deopt_instructions.h

Index: runtime/vm/deopt_instructions.h
diff --git a/runtime/vm/deopt_instructions.h b/runtime/vm/deopt_instructions.h
index 01a6974d696e8c22d434d1da0c6127b7b2979247..c1811f0b15326e3a8e1c148e8a3cba4c74fadb38 100644
--- a/runtime/vm/deopt_instructions.h
+++ b/runtime/vm/deopt_instructions.h
@@ -7,6 +7,7 @@
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
+#include "vm/code_descriptors.h"
 #include "vm/code_generator.h"
 #include "vm/deferred_objects.h"
 #include "vm/flow_graph_compiler.h"
@@ -57,6 +58,18 @@ class DeoptContext {
     return &source_frame_[index];
   }
 
+  // Returns index in stack slot notation where -1 is the first argument
+  // For DBC returns index directly relative to FP.
+  intptr_t GetStackSlot(intptr_t index) const {
+    ASSERT((0 <= index) && (index < source_frame_size_));
+    index -= num_args_;
+#if defined(TARGET_ARCH_DBC)
+    return index < 0 ? index - kDartFrameFixedSize : index;
+#else
+    return index < 0 ? index : index - kDartFrameFixedSize;
+#endif  // defined(TARGET_ARCH_DBC)
+  }
+
   intptr_t GetSourceFp() const;
   intptr_t GetSourcePp() const;
   intptr_t GetSourcePc() const;
@@ -153,6 +166,9 @@ class DeoptContext {
   // objects.
   void FillDestFrame();
 
+  // Allocate and prepare exceptions metadata for TrySync
+  intptr_t* CatchEntryState(intptr_t num_vars);
+
   // Materializes all deferred objects.  Returns the total number of
   // artificial arguments used during deoptimization.
   intptr_t MaterializeDeferredObjects();
@@ -271,7 +287,6 @@ class DeoptContext {
   DISALLOW_COPY_AND_ASSIGN(DeoptContext);
 };
 
-
 // Represents one deopt instruction, e.g, setup return address, store object,
 // store register, etc. The target is defined by instruction's position in
 // the deopt-info array.
@@ -319,6 +334,13 @@ class DeoptInstr : public ZoneAllocated {
 
   virtual void Execute(DeoptContext* deopt_context, intptr_t* dest_addr) = 0;
 
+  // Convert DeoptInstr to TrySync metadata entry.
+  virtual CatchEntryStatePair ToCatchEntryStatePair(DeoptContext* deopt_context,
+                                                    intptr_t dest_slot) {
+    UNREACHABLE();
+    return CatchEntryStatePair();
+  }
+
   virtual DeoptInstr::Kind kind() const = 0;
 
   bool Equals(const DeoptInstr& other) const {
@@ -412,6 +434,14 @@ class RegisterSource {
     }
   }
 
+  intptr_t StackSlot(DeoptContext* context) const {
+    if (is_register()) {
+      return raw_index();  // in DBC stack slots are registers.
+    } else {
+      return context->GetStackSlot(raw_index());
+    }
+  }
+
   intptr_t source_index() const { return source_index_; }
 
   const char* ToCString() const {