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| 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 | |
| 11 void 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 | |
| 50 void HMarkUnreachableBlocksPhase::Run() { | |
| 51 MarkUnreachableBlocks(); | |
| 52 } | |
| 53 | |
| 54 } // namespace internal | |
| 55 } // namespace v8 | |
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