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 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 const ZoneList<HBasicBlock*>* blocks = graph()->blocks(); 17 while (changed) { 18 changed = false; 19 for (int i = 0; i < blocks->length(); i++) { 20 HBasicBlock* block = blocks->at(i); 21 if (!block->IsReachable()) continue; 22 bool is_reachable = blocks->at(0) == block; 23 for (HPredecessorIterator it(block); !it.Done(); it.Advance()) { 24 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 if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) { 30 HBasicBlock* pred_succ; 31 bool known_pred_succ = 32 predecessor->end()->KnownSuccessorBlock(&pred_succ); 33 if (!known_pred_succ || pred_succ == block) { 34 is_reachable = true; 35 break; 36 } 37 } 38 if (block->is_osr_entry()) { 39 is_reachable = true; 40 } 41 } 42 if (!is_reachable) { 43 block->MarkUnreachable(); 44 changed = true; 45 } 46 } 47 } 48 } 49 50 51 void HMarkUnreachableBlocksPhase::Run() { 52 MarkUnreachableBlocks(); 53 } 54 55 } // namespace internal 56 } // namespace v8 57
