VM: Use BlockIterator in the optimizer consistently for iterating the flow graph

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, 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/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 70 matching lines @@
 
 
 // Optimize instance calls using ICData.
 void FlowGraphOptimizer::ApplyICData() {
   VisitBlocks();
 }
 
 
 void FlowGraphOptimizer::PopulateWithICData() {
   ASSERT(current_iterator_ == NULL);
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* entry = block_order_[i];
-    ForwardInstructionIterator it(entry);
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    ForwardInstructionIterator it(block_it.Current());
     for (; !it.Done(); it.Advance()) {
       Instruction* instr = it.Current();
       if (instr->IsInstanceCall()) {
         InstanceCallInstr* call = instr->AsInstanceCall();
         if (!call->HasICData()) {
           const Array& arguments_descriptor =
               Array::Handle(zone(),
                   ArgumentsDescriptor::New(call->ArgumentCount(),
                                            call->argument_names()));
           const ICData& ic_data = ICData::ZoneHandle(zone(), ICData::New(
@@ skipping 10 matching lines @@
 
 
 // Optimize instance calls using cid.  This is called after optimizer
 // converted instance calls to instructions. Any remaining
 // instance calls are either megamorphic calls, cannot be optimized or
 // have no runtime type feedback collected.
 // Attempts to convert an instance call (IC call) using propagated class-ids,
 // e.g., receiver class id, guarded-cid, or by guessing cid-s.
 void FlowGraphOptimizer::ApplyClassIds() {
   ASSERT(current_iterator_ == NULL);
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* entry = block_order_[i];
-    ForwardInstructionIterator it(entry);
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    ForwardInstructionIterator it(block_it.Current());
     current_iterator_ = &it;
     for (; !it.Done(); it.Advance()) {
       Instruction* instr = it.Current();
       if (instr->IsInstanceCall()) {
         InstanceCallInstr* call = instr->AsInstanceCall();
         if (call->HasICData()) {
           if (TryCreateICData(call)) {
             VisitInstanceCall(call);
           }
         }
@@ skipping 412 matching lines @@
 
 
 // Optimize (a << b) & c pattern: if c is a positive Smi or zero, then the
 // shift can be a truncating Smi shift-left and result is always Smi.
 // Merging occurs only per basic-block.
 void FlowGraphOptimizer::TryOptimizePatterns() {
   if (!FLAG_truncating_left_shift) return;
   ASSERT(current_iterator_ == NULL);
   GrowableArray<BinarySmiOpInstr*> div_mod_merge;
   GrowableArray<MathUnaryInstr*> sin_cos_merge;
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
     // Merging only per basic-block.
     div_mod_merge.Clear();
     sin_cos_merge.Clear();
-    BlockEntryInstr* entry = block_order_[i];
-    ForwardInstructionIterator it(entry);
+    ForwardInstructionIterator it(block_it.Current());
     current_iterator_ = &it;
     for (; !it.Done(); it.Advance()) {
       if (it.Current()->IsBinarySmiOp()) {
         BinarySmiOpInstr* binop = it.Current()->AsBinarySmiOp();
         if (binop->op_kind() == Token::kBIT_AND) {
           OptimizeLeftShiftBitAndSmiOp(binop,
                                        binop->left()->definition(),
                                        binop->right()->definition());
         } else if ((binop->op_kind() == Token::kTRUNCDIV) ||
                    (binop->op_kind() == Token::kMOD)) {
@@ skipping 20 matching lines @@
     }
     TryMergeTruncDivMod(&div_mod_merge);
     TryMergeMathUnary(&sin_cos_merge);
     current_iterator_ = NULL;
   }
 }
 
 
 bool FlowGraphOptimizer::Canonicalize() {
   bool changed = false;
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* entry = block_order_[i];
-    for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
+
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    for (ForwardInstructionIterator it(block_it.Current());
+         !it.Done();
+         it.Advance()) {
       Instruction* current = it.Current();
       if (current->HasUnmatchedInputRepresentations()) {
         // Can't canonicalize this instruction until all conversions for its
         // inputs are inserted.
         continue;
       }
 
       Instruction* replacement = current->Canonicalize(flow_graph());
 
       if (replacement != current) {
@@ skipping 211 matching lines @@
     }
   }
 
   phi->set_representation(unboxed);
 }
 
 
 void FlowGraphOptimizer::SelectRepresentations() {
   // Conservatively unbox all phis that were proven to be of Double,
   // Float32x4, or Int32x4 type.
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    JoinEntryInstr* join_entry = block_order_[i]->AsJoinEntry();
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    JoinEntryInstr* join_entry = block_it.Current()->AsJoinEntry();
     if (join_entry != NULL) {
       for (PhiIterator it(join_entry); !it.Done(); it.Advance()) {
         PhiInstr* phi = it.Current();
         UnboxPhi(phi);
       }
     }
   }
 
   // Process all instructions and insert conversions where needed.
-  GraphEntryInstr* graph_entry = block_order_[0]->AsGraphEntry();
+  GraphEntryInstr* graph_entry = flow_graph_->graph_entry();
 
   // Visit incoming parameters and constants.
   for (intptr_t i = 0; i < graph_entry->initial_definitions()->length(); i++) {
     InsertConversionsFor((*graph_entry->initial_definitions())[i]);
   }
 
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* entry = block_order_[i];
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    BlockEntryInstr* entry = block_it.Current();
     JoinEntryInstr* join_entry = entry->AsJoinEntry();
     if (join_entry != NULL) {
       for (PhiIterator it(join_entry); !it.Done(); it.Advance()) {
         PhiInstr* phi = it.Current();
         ASSERT(phi != NULL);
         ASSERT(phi->is_alive());
         InsertConversionsFor(phi);
       }
     }
     CatchBlockEntryInstr* catch_entry = entry->AsCatchBlockEntry();
@@ skipping 3069 matching lines @@
   // save enough range information in the ICData to drive this decision.
 }
 #endif
 
 
 void FlowGraphOptimizer::EliminateEnvironments() {
   // After this pass we can no longer perform LICM and hoist instructions
   // that can deoptimize.
 
   flow_graph_->disallow_licm();
-  for (intptr_t i = 0; i < block_order_.length(); ++i) {
-    BlockEntryInstr* block = block_order_[i];
+  for (BlockIterator block_it = flow_graph_->reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    BlockEntryInstr* block = block_it.Current();
     block->RemoveEnvironment();
     for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
       Instruction* current = it.Current();
       if (!current->CanDeoptimize()) {
         // TODO(srdjan): --source-lines needs deopt environments to get at
         // the code for this instruction, however, leaving the environment
         // changes code.
         current->RemoveEnvironment();
       }
     }
   }
 }
 
 
 }  // namespace dart