Build and use stack maps in the SSA compiler.

runtime/vm/locations.h

Index: runtime/vm/locations.h
diff --git a/runtime/vm/locations.h b/runtime/vm/locations.h
index 2334a28af7c5119de3643d6bac1723be0efc481d..6e4393ca6a797b7fe8e340687aa270a6547c086c 100644
--- a/runtime/vm/locations.h
+++ b/runtime/vm/locations.h
@@ -268,6 +268,8 @@ class LocationSummary : public ZoneAllocated {
     output_location_ = loc;
   }
 
+  BitmapBuilder* stack_bitmap() const { return stack_bitmap_; }
+
   bool is_call() const {
     return is_call_;
   }
@@ -283,7 +285,7 @@ class LocationSummary : public ZoneAllocated {
   GrowableArray<Location> input_locations_;
   GrowableArray<Location> temp_locations_;
   Location output_location_;
-
+  BitmapBuilder* stack_bitmap_;
   const bool is_call_;
 };