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Diffstat (limited to 'deps/v8/src/hydrogen-mark-unreachable.cc')
-rw-r--r-- | deps/v8/src/hydrogen-mark-unreachable.cc | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/deps/v8/src/hydrogen-mark-unreachable.cc b/deps/v8/src/hydrogen-mark-unreachable.cc new file mode 100644 index 0000000000..d7c5ed2b18 --- /dev/null +++ b/deps/v8/src/hydrogen-mark-unreachable.cc @@ -0,0 +1,77 @@ +// Copyright 2013 the V8 project authors. All rights reserved. +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following +// disclaimer in the documentation and/or other materials provided +// with the distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived +// from this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +#include "hydrogen-mark-unreachable.h" + +namespace v8 { +namespace internal { + + +void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() { + // If there is unreachable code in the graph, propagate the unreachable marks + // using a fixed-point iteration. + bool changed = true; + const ZoneList<HBasicBlock*>* blocks = graph()->blocks(); + while (changed) { + changed = false; + for (int i = 0; i < blocks->length(); i++) { + HBasicBlock* block = blocks->at(i); + if (!block->IsReachable()) continue; + bool is_reachable = blocks->at(0) == block; + for (HPredecessorIterator it(block); !it.Done(); it.Advance()) { + HBasicBlock* predecessor = it.Current(); + // A block is reachable if one of its predecessors is reachable, + // doesn't deoptimize and either is known to transfer control to the + // block or has a control flow instruction for which the next block + // cannot be determined. + if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) { + HBasicBlock* pred_succ; + bool known_pred_succ = + predecessor->end()->KnownSuccessorBlock(&pred_succ); + if (!known_pred_succ || pred_succ == block) { + is_reachable = true; + break; + } + } + if (block->is_osr_entry()) { + is_reachable = true; + } + } + if (!is_reachable) { + block->MarkUnreachable(); + changed = true; + } + } + } +} + + +void HMarkUnreachableBlocksPhase::Run() { + MarkUnreachableBlocks(); +} + +} } // namespace v8::internal |