Line data    Source code

       1             : // Copyright 2013 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #include "src/crankshaft/hydrogen-mark-unreachable.h"
       6             : #include "src/objects-inl.h"
       7             : 
       8             : namespace v8 {
       9             : namespace internal {
      10             : 
      11             : 
      12      567459 : void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() {
      13             :   // If there is unreachable code in the graph, propagate the unreachable marks
      14             :   // using a fixed-point iteration.
      15             :   bool changed = true;
      16      567459 :   const ZoneList<HBasicBlock*>* blocks = graph()->blocks();
      17     1726539 :   while (changed) {
      18             :     changed = false;
      19    26467762 :     for (int i = 0; i < blocks->length(); i++) {
      20    26467761 :       HBasicBlock* block = blocks->at(i);
      21    12938070 :       if (!block->IsReachable()) continue;
      22     9920165 :       bool is_reachable = blocks->at(0) == block;
      23    11189348 :       for (HPredecessorIterator it(block); !it.Done(); it.Advance()) {
      24     8367046 :         HBasicBlock* predecessor = it.Current();
      25             :         // A block is reachable if one of its predecessors is reachable,
      26             :         // doesn't deoptimize and either is known to transfer control to the
      27             :         // block or has a control flow instruction for which the next block
      28             :         // cannot be determined.
      29    17940291 :         if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) {
      30             :           HBasicBlock* pred_succ;
      31             :           bool known_pred_succ =
      32     8367046 :               predecessor->end()->KnownSuccessorBlock(&pred_succ);
      33     8367038 :           if (!known_pred_succ || pred_succ == block) {
      34             :             is_reachable = true;
      35     8258425 :             break;
      36             :           }
      37             :         }
      38     1269183 :         if (block->is_osr_entry()) {
      39             :           is_reachable = true;
      40             :         }
      41             :       }
      42     9920165 :       if (!is_reachable) {
      43     1063708 :         block->MarkUnreachable();
      44             :         changed = true;
      45             :       }
      46             :     }
      47             :   }
      48      567460 : }
      49             : 
      50             : 
      51      567457 : void HMarkUnreachableBlocksPhase::Run() {
      52      567457 :   MarkUnreachableBlocks();
      53      567460 : }
      54             : 
      55             : }  // namespace internal
      56             : }  // namespace v8