Add hints when resolving phies and register constraints.

runtime/vm/flow_graph_allocator.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_ALLOCATOR_H_
 #define VM_FLOW_GRAPH_ALLOCATOR_H_
 
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 
@@ skipping 247 matching lines @@
 
 
 // UsePosition represents a single use of an SSA value by some instruction.
 // It points to a location slot which either tells register allocator
 // where instruction expects the value (if slot contains a fixed location) or
 // asks register allocator to allocate storage (register or spill slot) for
 // this use with certain properties (if slot contains an unallocated location).
 class UsePosition : public ZoneAllocated {
  public:
   UsePosition(intptr_t pos, UsePosition* next, Location* location_slot)
-      : pos_(pos), location_slot_(location_slot), next_(next) { }
+      : pos_(pos), location_slot_(location_slot), hint_(NULL), next_(next) { }
 
   Location* location_slot() const { return location_slot_; }
   void set_location_slot(Location* location_slot) {
     location_slot_ = location_slot;
   }
 
+  Location hint() const {
+    ASSERT(HasHint());
+    return *hint_;
+  }
+
+  void set_hint(Location* hint) {
+    hint_ = hint;
+  }
+
+  bool HasHint() const {
+    return (hint_ != NULL) && !hint_->IsUnallocated();
+  }
+
+
   void set_next(UsePosition* next) { next_ = next; }
   UsePosition* next() const { return next_; }
 
   intptr_t pos() const { return pos_; }
 
-  bool HasHint() const {
-    return (location_slot() != NULL) && (location_slot()->IsRegister());
-  }
-
-  Location hint() const {
-    ASSERT(HasHint());
-    return *location_slot();
-  }
-
  private:
   const intptr_t pos_;
   Location* location_slot_;
+  Location* hint_;
   UsePosition* next_;
 
   DISALLOW_COPY_AND_ASSIGN(UsePosition);
 };
 
 
 // UseInterval represents a holeless half open interval of liveness for a given
 // SSA value: [start, end) in terms of lifetime positions that
 // NumberInstructions assigns to instructions.  Register allocator has to keep
 // a value live in the register or in a spill slot from start position and until
@@ skipping 97 matching lines @@
     assigned_location_ = location;
   }
 
   void set_spill_slot(Location spill_slot) {
     spill_slot_ = spill_slot;
   }
 
   void DefineAt(intptr_t pos);
 
   void AddUse(intptr_t pos, Location* location_slot);
+  void AddHintedUse(intptr_t pos, Location* location_slot, Location* hint);
+
   void AddUseInterval(intptr_t start, intptr_t end);
 
   void Print();
 
   void AssignLocation(UseInterval* use, Location loc);
 
   LiveRange* SplitAt(intptr_t pos);
 
   bool CanCover(intptr_t pos) const {
     return (Start() <= pos) && (pos < End());
@@ skipping 30 matching lines @@
 
   AllocationFinger finger_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRange);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_ALLOCATOR_H_