Generate smaller unoptimized code for certain expressions.

runtime/vm/flow_graph.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/flow_graph.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/intermediate_language.h"
 #include "vm/longjump.h"
@@ skipping 850 matching lines @@
       LoadLocalInstr* load = definition->AsLoadLocal();
       StoreLocalInstr* store = definition->AsStoreLocal();
       PushTempInstr* push = definition->AsPushTemp();
       DropTempsInstr* drop = definition->AsDropTemps();
       ConstantInstr* constant = definition->AsConstant();
       if ((load != NULL) ||
           (store != NULL) ||
           (push != NULL) ||
           (drop != NULL) ||
           (constant != NULL)) {
-        intptr_t index;
-        Definition* result;
+        Definition* result = NULL;
         if (store != NULL) {
           // Update renaming environment.
-          index = store->local().BitIndexIn(num_non_copied_params_);
+          intptr_t index = store->local().BitIndexIn(num_non_copied_params_);
           result = store->value()->definition();
 
           if (variable_liveness->IsStoreAlive(block_entry, store)) {
             (*env)[index] = result;
           } else {
             (*env)[index] = constant_dead();
           }
         } else if (load != NULL) {
           // The graph construction ensures we do not have an unused LoadLocal
           // computation.
           ASSERT(definition->is_used());
-          index = load->local().BitIndexIn(num_non_copied_params_);
+          intptr_t index = load->local().BitIndexIn(num_non_copied_params_);
           result = (*env)[index];
 
           PhiInstr* phi = result->AsPhi();
           if ((phi != NULL) && !phi->is_alive()) {
             phi->mark_alive();
             live_phis->Add(phi);
           }
 
           if (variable_liveness->IsLastLoad(block_entry, load)) {
             (*env)[index] = constant_dead();
           }
         } else if (push != NULL) {
           result = push->value()->definition();
           env->Add(result);
           it.RemoveCurrentFromGraph();
           continue;
         } else if (drop != NULL) {
           // Drop temps from the environment.
           for (intptr_t j = 0; j < drop->num_temps(); j++) {
             env->RemoveLast();
           }
-          result = drop->value()->definition();
+          if (drop->value() != NULL) {
+            result = drop->value()->definition();
+          }
+          ASSERT((drop->value() != NULL) || !drop->is_used());
         } else {
           ASSERT(definition->is_used());
           result = GetConstant(constant->value());
         }
         // Update expression stack or remove from graph.
         if (definition->is_used()) {
           ASSERT(result != NULL);
           env->Add(result);
           // We remove load/store/constant instructions when we find their
           // use in 2a.
@@ skipping 296 matching lines @@
 }
 
 
 bool BlockEffects::IsSideEffectFreePath(BlockEntryInstr* from,
                                         BlockEntryInstr* to) const {
   return available_at_[to->postorder_number()]->Contains(
       from->postorder_number());
 }
 
 }  // namespace dart