Refactor to support multiple outputs in location summary

runtime/vm/locations.h

Index: runtime/vm/locations.h
diff --git a/runtime/vm/locations.h b/runtime/vm/locations.h
index 89e6702abb27c3cf73b2e3923c40eb8926beea43..5032783f12d097cb3f90da694e30027f8ed28ca0 100644
--- a/runtime/vm/locations.h
+++ b/runtime/vm/locations.h
@@ -396,7 +396,8 @@ class LocationSummary : public ZoneAllocated {
 
   LocationSummary(intptr_t input_count,
                   intptr_t temp_count,
-                  LocationSummary::ContainsCall contains_call);
+                  LocationSummary::ContainsCall contains_call,
+                  intptr_t output_count = 1);

[srdjan, 2014/03/20 23:04:23]

The count is kind of our of order. Instead of the optional argument you could
use  AddOutput (similar to AddTemp). Or maybe have a second constructor with 4
arguments, all counts together.

[Cutch, 2014/03/21 14:36:46]

Done.

 
   intptr_t input_count() const {
     return input_locations_.length();
@@ -437,17 +438,21 @@ class LocationSummary : public ZoneAllocated {
     temp_locations_.Add(loc);
   }
 
-  Location out() const {
-    return output_location_;
+  intptr_t output_count() const {
+    return output_locations_.length();
   }
 
-  Location* out_slot() {
-    return &output_location_;
+  Location out(intptr_t index) const {
+    return output_locations_[index];
   }
 
-  void set_out(Location loc) {
+  Location* out_slot(intptr_t index) {
+    return &output_locations_[index];
+  }
+
+  void set_out(intptr_t index, Location loc) {
     ASSERT(!always_calls() || (loc.IsMachineRegister() || loc.IsInvalid()));
-    output_location_ = loc;
+    output_locations_[index] = loc;
   }
 
   BitmapBuilder* stack_bitmap() const { return stack_bitmap_; }
@@ -471,10 +476,10 @@ class LocationSummary : public ZoneAllocated {
   }
 
  private:
-  // TODO(vegorov): replace with ZoneArray.
-  GrowableArray<Location> input_locations_;
-  GrowableArray<Location> temp_locations_;
-  Location output_location_;
+  ZoneGrowableArray<Location> input_locations_;

[Florian Schneider, 2014/03/21 10:47:07]

I wonder how often we actually want to add/remove operands from the location
summary. With growable arrays, we use at least 3*5 words for a (1, 1, 1)-operand
summary, which really contains 3 words of payload.

Have you considered using EmbeddedArray which is used in
intermediate_language.h?

[Cutch, 2014/03/21 14:36:46]

Good point but I would prefer to do that change in a follow up CL.

+  ZoneGrowableArray<Location> temp_locations_;
+  ZoneGrowableArray<Location> output_locations_;
+
   BitmapBuilder* stack_bitmap_;
 
   const ContainsCall contains_call_;