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// 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
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