Compute the def-use list on-demand by walking the dominator tree.

runtime/vm/flow_graph_optimizer.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_optimizer.h"
 
 #include "vm/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/hash_map.h"
 #include "vm/il_printer.h"
@@ skipping 135 matching lines @@
 static bool HasOnlyTwoDouble(const ICData& ic_data) {
   return (ic_data.NumberOfChecks() == 1) &&
       ICDataHasReceiverArgumentClassIds(ic_data, kDoubleCid, kDoubleCid);
 }
 
 
 static void RemovePushArguments(InstanceCallComp* comp) {
   // Remove original push arguments.
   for (intptr_t i = 0; i < comp->ArgumentCount(); ++i) {
     PushArgumentInstr* push = comp->ArgumentAt(i);
-    // TODO(zerny): Currently the register allocator replaces unused pushes with
-    // their definitions. To do so here, we need first to link uses to their
-    // instructions and input index. Here push->ReplaceUsesWith requires that
-    // push->value() is a UseVal.
-    // (See FlowGraphAllocator::EliminateEnvironmentUses).
-    push->set_use_list(NULL);
     push->RemoveFromGraph();
   }
 }
 
 
 // Returns true if all targets are the same.
 // TODO(srdjan): if targets are native use their C_function to compare.
 static bool HasOneTarget(const ICData& ic_data) {
   ASSERT(ic_data.NumberOfChecks() > 0);
   const Function& first_target = Function::Handle(ic_data.GetTargetAt(0));
@@ skipping 156 matching lines @@
     bin_op->set_ic_data(comp->ic_data());
     instr->set_computation(bin_op);
     RemovePushArguments(comp);
   } else {
     ASSERT(operands_type == kSmiCid);
     Value* left = comp->ArgumentAt(0)->value();
     Value* right = comp->ArgumentAt(1)->value();
     // Insert two smi checks and attach a copy of the original
     // environment because the smi operation can still deoptimize.
     InsertCheckBefore(instr,
-                      new CheckSmiComp(left, comp),
+                      new CheckSmiComp(left->CopyValue(), comp),
                       instr->env()->Copy());
     InsertCheckBefore(instr,
-                      new CheckSmiComp(right, comp),
+                      new CheckSmiComp(right->CopyValue(), comp),
                       instr->env()->Copy());
     BinarySmiOpComp* bin_op = new BinarySmiOpComp(op_kind,
                                                   comp,
                                                   left,
                                                   right);
     bin_op->set_ic_data(comp->ic_data());
     instr->set_computation(bin_op);
     RemovePushArguments(comp);
   }
   return true;
@@ skipping 56 matching lines @@
     if (!HasOneTarget(ic_data)) {
       // TODO(srdjan): Implement for mutiple targets.
       return false;
     }
     // Inline implicit instance getter.
     const String& field_name =
         String::Handle(Field::NameFromGetter(comp->function_name()));
     const Field& field = Field::Handle(GetField(class_ids[0], field_name));
     ASSERT(!field.IsNull());
 
-    AddCheckClass(instr, comp, comp->ArgumentAt(0)->value());
+    AddCheckClass(instr, comp, comp->ArgumentAt(0)->value()->CopyValue());
     LoadInstanceFieldComp* load =
         new LoadInstanceFieldComp(field,
                                   comp->ArgumentAt(0)->value(),
                                   NULL);  // Can not deoptimize.
     instr->set_computation(load);
     RemovePushArguments(comp);
     return true;
   }
 
   // Not an implicit getter.
@@ skipping 159 matching lines @@
     // Not an implicit setter.
     // TODO(srdjan): Inline special setters.
     return false;
   }
   // Inline implicit instance setter.
   const String& field_name =
       String::Handle(Field::NameFromSetter(comp->function_name()));
   const Field& field = Field::Handle(GetField(class_id, field_name));
   ASSERT(!field.IsNull());
 
-  AddCheckClass(instr, comp, comp->ArgumentAt(0)->value());
+  AddCheckClass(instr, comp, comp->ArgumentAt(0)->value()->CopyValue());
   StoreInstanceFieldComp* store = new StoreInstanceFieldComp(
       field,
       comp->ArgumentAt(0)->value(),
       comp->ArgumentAt(1)->value(),
       NULL);  // Can not deoptimize.
   instr->set_computation(store);
   RemovePushArguments(comp);
   return true;
 }
 
@@ skipping 366 matching lines @@
         OS::Print("Replacing v%d with v%d\n",
                   instr->ssa_temp_index(),
                   result->ssa_temp_index());
       }
     }
   }
 }
 
 
 }  // namespace dart