Make constants computations instead of values.

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 85 matching lines @@
       if (use == NULL) continue;
       use->set_instruction(NULL);
       use->set_use_index(-1);
       use->set_next_use(NULL);
     }
   }
 }
 
 
 bool FlowGraph::ResetUseLists() {
+  // Reset global constants.
+  ResetUseListsInInstruction(graph_entry_->constant_null());
+
   // Reset definitions referenced from the start environment.
   for (intptr_t i = 0; i < graph_entry_->start_env()->values().length(); ++i) {
     UseVal* env_use = graph_entry_->start_env()->values()[i]->AsUse();
     if (env_use != NULL) ResetUseListsInInstruction(env_use->definition());
   }
+
   // Reset phis in join entries and the instructions in each block.
   for (intptr_t i = 0; i < preorder_.length(); ++i) {
     BlockEntryInstr* entry = preorder_[i];
     JoinEntryInstr* join = entry->AsJoinEntry();
     if (join != NULL && join->phis() != NULL) {
       for (intptr_t i = 0; i < join->phis()->length(); ++i) {
         PhiInstr* phi = (*join->phis())[i];
         if (phi != NULL) ResetUseListsInInstruction(phi);
       }
     }
@@ skipping 35 matching lines @@
          use != NULL;
          use = use->next_use()) {
       ASSERT(defn == use->definition());
       ASSERT(use == use->instruction()->env()->values()[use->use_index()]);
     }
   }
 }
 
 
 bool FlowGraph::ValidateUseLists() {
+  // Validate global constants.
+  ValidateUseListsInInstruction(graph_entry_->constant_null());
+
   // Validate definitions referenced from the start environment.
   for (intptr_t i = 0; i < graph_entry_->start_env()->values().length(); ++i) {
     UseVal* env_use = graph_entry_->start_env()->values()[i]->AsUse();
     if (env_use != NULL) ValidateUseListsInInstruction(env_use->definition());
   }
+
   // Validate phis in join entries and the instructions in each block.
   for (intptr_t i = 0; i < preorder_.length(); ++i) {
     BlockEntryInstr* entry = preorder_[i];
     JoinEntryInstr* join = entry->AsJoinEntry();
     if (join != NULL && join->phis() != NULL) {
       for (intptr_t i = 0; i < join->phis()->length(); ++i) {
         PhiInstr* phi = (*join->phis())[i];
         if (phi != NULL) ValidateUseListsInInstruction(phi);
       }
     }
@@ skipping 294 matching lines @@
   }
 }
 
 
 void FlowGraph::Rename(GrowableArray<PhiInstr*>* live_phis) {
   // TODO(fschneider): Support catch-entry.
   if (graph_entry_->SuccessorCount() > 1) {
     Bailout("Catch-entry support in SSA.");
   }
 
+  // Name global constants.
+  graph_entry_->constant_null()->set_ssa_temp_index(alloc_ssa_temp_index());
+
   // Initialize start environment.
   GrowableArray<Definition*> start_env(variable_count());
   for (intptr_t i = 0; i < parameter_count(); ++i) {
     ParameterInstr* param = new ParameterInstr(i);
     param->set_ssa_temp_index(alloc_ssa_temp_index());  // New SSA temp.
     start_env.Add(param);
   }
 
-  // All locals are initialized with #null.
-  Definition* null_defn =
-      new BindInstr(BindInstr::kUsed,
-                    new MaterializeComp(new ConstantVal(Object::ZoneHandle())));
-  // The null definition should not appear in input positions.
-  ASSERT(null_defn->ssa_temp_index() == -1);
+  // All locals are initialized with #null.  Use the global definition, uses
+  // will be created in the Environment constructor.
   while (start_env.length() < variable_count()) {
-    start_env.Add(null_defn);
+    start_env.Add(graph_entry_->constant_null());

[Kevin Millikin (Google), 2012/08/29 09:56:00]

This is a bit dodgy, because there are now multiple occurrences of this single
definition.  I can fix that by making a proper environment instead of a list of
definitions here.

   }
   graph_entry_->set_start_env(
       new Environment(start_env, non_copied_parameter_count_));
 
   BlockEntryInstr* normal_entry = graph_entry_->SuccessorAt(0);
   ASSERT(normal_entry != NULL);  // Must have entry.
   GrowableArray<Definition*> env(variable_count());
   env.AddArray(start_env);
   RenameRecursive(normal_entry, &env, live_phis);
 }
 
 
-// Helper to either use the constant value of a definition or the definition.
-static Value* UseDefinition(Definition* defn) {
-  if (defn->IsBind() && defn->AsBind()->computation()->IsMaterialize()) {
-    return defn->AsBind()->computation()->AsMaterialize()->constant_val();
-  } else {
-    return new UseVal(defn);
-  }
-}
-
-
 void FlowGraph::RenameRecursive(BlockEntryInstr* block_entry,
                                 GrowableArray<Definition*>* env,
                                 GrowableArray<PhiInstr*>* live_phis) {
   // 1. Process phis first.
   if (block_entry->IsJoinEntry()) {
     JoinEntryInstr* join = block_entry->AsJoinEntry();
     if (join->phis() != NULL) {
       for (intptr_t i = 0; i < join->phis()->length(); ++i) {
         PhiInstr* phi = (*join->phis())[i];
         if (phi != NULL) {
@@ skipping 106 matching lines @@
       block_entry->last_instruction()->SuccessorAt(0)->IsJoinEntry()) {
     JoinEntryInstr* successor =
         block_entry->last_instruction()->SuccessorAt(0)->AsJoinEntry();
     intptr_t pred_index = successor->IndexOfPredecessor(block_entry);
     ASSERT(pred_index >= 0);
     if (successor->phis() != NULL) {
       for (intptr_t i = 0; i < successor->phis()->length(); ++i) {
         PhiInstr* phi = (*successor->phis())[i];
         if (phi != NULL) {
           // Rename input operand.
-          phi->SetInputAt(pred_index, UseDefinition((*env)[i]));
+          phi->SetInputAt(pred_index, new UseVal((*env)[i]));
         }
       }
     }
   }
 }
 
 
 void FlowGraph::MarkLivePhis(GrowableArray<PhiInstr*>* live_phis) {
   while (!live_phis->is_empty()) {
     PhiInstr* phi = live_phis->Last();
@@ skipping 17 matching lines @@
   intptr_t len = OS::SNPrint(NULL, 0, kFormat, function_name, reason) + 1;
   char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, kFormat, function_name, reason);
   const Error& error = Error::Handle(
       LanguageError::New(String::Handle(String::New(chars))));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart