jkummerow@chromium.org | d8a3a14 | 2013-10-03 12:15:05 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Redistribution and use in source and binary forms, with or without |
| 3 | // modification, are permitted provided that the following conditions are |
| 4 | // met: |
| 5 | // |
| 6 | // * Redistributions of source code must retain the above copyright |
| 7 | // notice, this list of conditions and the following disclaimer. |
| 8 | // * Redistributions in binary form must reproduce the above |
| 9 | // copyright notice, this list of conditions and the following |
| 10 | // disclaimer in the documentation and/or other materials provided |
| 11 | // with the distribution. |
| 12 | // * Neither the name of Google Inc. nor the names of its |
| 13 | // contributors may be used to endorse or promote products derived |
| 14 | // from this software without specific prior written permission. |
| 15 | // |
| 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | |
| 28 | #include "hydrogen-mark-unreachable.h" |
| 29 | |
| 30 | namespace v8 { |
| 31 | namespace internal { |
| 32 | |
| 33 | |
| 34 | void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() { |
| 35 | // If there is unreachable code in the graph, propagate the unreachable marks |
| 36 | // using a fixed-point iteration. |
| 37 | bool changed = true; |
| 38 | const ZoneList<HBasicBlock*>* blocks = graph()->blocks(); |
| 39 | while (changed) { |
| 40 | changed = false; |
| 41 | for (int i = 0; i < blocks->length(); i++) { |
| 42 | HBasicBlock* block = blocks->at(i); |
| 43 | if (!block->IsReachable()) continue; |
| 44 | bool is_reachable = blocks->at(0) == block; |
| 45 | for (HPredecessorIterator it(block); !it.Done(); it.Advance()) { |
| 46 | HBasicBlock* predecessor = it.Current(); |
| 47 | // A block is reachable if one of its predecessors is reachable, |
| 48 | // doesn't deoptimize and either is known to transfer control to the |
| 49 | // block or has a control flow instruction for which the next block |
| 50 | // cannot be determined. |
| 51 | if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) { |
| 52 | HBasicBlock* pred_succ; |
| 53 | bool known_pred_succ = |
| 54 | predecessor->end()->KnownSuccessorBlock(&pred_succ); |
| 55 | if (!known_pred_succ || pred_succ == block) { |
| 56 | is_reachable = true; |
| 57 | break; |
| 58 | } |
| 59 | } |
| 60 | if (block->is_osr_entry()) { |
| 61 | is_reachable = true; |
| 62 | } |
| 63 | } |
| 64 | if (!is_reachable) { |
| 65 | block->MarkUnreachable(); |
| 66 | changed = true; |
| 67 | } |
| 68 | } |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | |
| 73 | void HMarkUnreachableBlocksPhase::Run() { |
| 74 | MarkUnreachableBlocks(); |
| 75 | } |
| 76 | |
| 77 | } } // namespace v8::internal |