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/hydrogen-mark-unreachable.h" 6 7 namespace v8 { 8 namespace internal { 9 10 MarkUnreachableBlocks()11void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() { 12 // If there is unreachable code in the graph, propagate the unreachable marks 13 // using a fixed-point iteration. 14 bool changed = true; 15 const ZoneList<HBasicBlock*>* blocks = graph()->blocks(); 16 while (changed) { 17 changed = false; 18 for (int i = 0; i < blocks->length(); i++) { 19 HBasicBlock* block = blocks->at(i); 20 if (!block->IsReachable()) continue; 21 bool is_reachable = blocks->at(0) == block; 22 for (HPredecessorIterator it(block); !it.Done(); it.Advance()) { 23 HBasicBlock* predecessor = it.Current(); 24 // A block is reachable if one of its predecessors is reachable, 25 // doesn't deoptimize and either is known to transfer control to the 26 // block or has a control flow instruction for which the next block 27 // cannot be determined. 28 if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) { 29 HBasicBlock* pred_succ; 30 bool known_pred_succ = 31 predecessor->end()->KnownSuccessorBlock(&pred_succ); 32 if (!known_pred_succ || pred_succ == block) { 33 is_reachable = true; 34 break; 35 } 36 } 37 if (block->is_osr_entry()) { 38 is_reachable = true; 39 } 40 } 41 if (!is_reachable) { 42 block->MarkUnreachable(); 43 changed = true; 44 } 45 } 46 } 47 } 48 49 Run()50void HMarkUnreachableBlocksPhase::Run() { 51 MarkUnreachableBlocks(); 52 } 53 54 } } // namespace v8::internal 55