Improve register usage for StoreInstanceField.

runtime/vm/flow_graph_compiler.cc

 // 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
@@ skipping 642 matching lines @@
     blocked_registers[TMP] = true;
   }
 
   // Allocate all unallocated input locations.
   const bool should_pop = !instr->IsPushArgument();
   for (intptr_t i = locs->input_count() - 1; i >= 0; i--) {
     Location loc = locs->in(i);
     Register reg = kNoRegister;
     if (loc.IsRegister()) {
       reg = loc.reg();
-    } else if (loc.IsUnallocated()) {
-      ASSERT((loc.policy() == Location::kRequiresRegister) ||
-             (loc.policy() == Location::kWritableRegister));
+    } else if (loc.IsUnallocated() || loc.IsConstant()) {
+      ASSERT(loc.IsConstant() ||
+             ((loc.policy() == Location::kRequiresRegister) ||
+              (loc.policy() == Location::kWritableRegister)));
       reg = AllocateFreeRegister(blocked_registers);
       locs->set_in(i, Location::RegisterLocation(reg));
     }
+    ASSERT(reg != kNoRegister);
 
     // Inputs are consumed from the simulated frame. In case of a call argument
     // we leave it until the call instruction.
     if (should_pop) {
       assembler()->PopRegister(reg);
     }
   }
 
   // Allocate all unallocated temp locations.
   for (intptr_t i = 0; i < locs->temp_count(); i++) {
@@ skipping 172 matching lines @@
     case ABOVE:         return unsigned_left > unsigned_right;
     case ABOVE_EQUAL:   return unsigned_left >= unsigned_right;
     default:
       UNIMPLEMENTED();
       return false;
   }
 }
 
 
 }  // namespace dart