v8/src/hydrogen-sce.cc

63 lines
2.6 KiB
C++

// 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-sce.h"
#include "v8.h"
namespace v8 {
namespace internal {
void HStackCheckEliminationPhase::Run() {
// For each loop block walk the dominator tree from the backwards branch to
// the loop header. If a call instruction is encountered the backwards branch
// is dominated by a call and the stack check in the backwards branch can be
// removed.
for (int i = 0; i < graph()->blocks()->length(); i++) {
HBasicBlock* block = graph()->blocks()->at(i);
if (block->IsLoopHeader()) {
HBasicBlock* back_edge = block->loop_information()->GetLastBackEdge();
HBasicBlock* dominator = back_edge;
while (true) {
for (HInstructionIterator it(dominator); !it.Done(); it.Advance()) {
if (it.Current()->IsCall()) {
block->loop_information()->stack_check()->Eliminate();
break;
}
}
// Done when the loop header is processed.
if (dominator == block) break;
// Move up the dominator tree.
dominator = dominator->dominator();
}
}
}
}
} } // namespace v8::internal