Reland "VM: Handle null-comparisons in the flow graph type propagation"

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/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 1024 matching lines @@
       Environment::From(zone(), *env, num_non_copied_params_, parsed_function_);
   if (instr->IsClosureCall()) {
     deopt_env =
         deopt_env->DeepCopy(zone(), deopt_env->Length() - instr->InputCount());
   }
   instr->SetEnvironment(deopt_env);
   for (Environment::DeepIterator it(deopt_env); !it.Done(); it.Advance()) {
     Value* use = it.CurrentValue();
     use->definition()->AddEnvUse(use);
   }
-  if (instr->CanDeoptimize()) {
+  if (instr->ComputeCanDeoptimize()) {
     instr->env()->set_deopt_id(instr->deopt_id());
   }
 }
 
 
 void FlowGraph::RenameRecursive(BlockEntryInstr* block_entry,
                                 GrowableArray<Definition*>* env,
                                 GrowableArray<PhiInstr*>* live_phis,
                                 VariableLivenessAnalysis* variable_liveness) {
   // 1. Process phis first.
@@ skipping 957 matching lines @@
 
   disallow_licm();
   for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
        block_it.Advance()) {
     BlockEntryInstr* block = block_it.Current();
     if (!block->IsCatchBlockEntry()) {
       block->RemoveEnvironment();
     }
     for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
       Instruction* current = it.Current();
-      if (!current->CanDeoptimize() &&
+      if (!current->ComputeCanDeoptimize() &&
           (!current->MayThrow() || !current->GetBlock()->InsideTryBlock())) {
         // Instructions that can throw need an environment for optimized
         // try-catch.
         // TODO(srdjan): --source-lines needs deopt environments to get at
         // the code for this instruction, however, leaving the environment
         // changes code.
         current->RemoveEnvironment();
       }
     }
   }
@@ skipping 265 matching lines @@
                                                 Representation rep,
                                                 intptr_t cid) {
   ExtractNthOutputInstr* extract =
       new (Z) ExtractNthOutputInstr(new (Z) Value(instr), index, rep, cid);
   instr->ReplaceUsesWith(extract);
   InsertAfter(instr, extract, NULL, FlowGraph::kValue);
 }
 
 
 }  // namespace dart