908a7dc2a8
- Detect unreachable basic blocks of code either following an unconditional deopt or after a provably untaken branch of HBranch or HCompareObjectEqAndBranch instructions. - Emit dummy uses in unreachable blocks during Hydrogen -> Lithium translation. BUG=chromium:258519 R=jkummerow@chromium.org, mstarzinger@chromium.org Review URL: https://codereview.chromium.org/22876009 git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17073 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
78 lines
3.1 KiB
C++
78 lines
3.1 KiB
C++
// Copyright 2013 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "hydrogen-mark-unreachable.h"
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namespace v8 {
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namespace internal {
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void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() {
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// If there is unreachable code in the graph, propagate the unreachable marks
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// using a fixed-point iteration.
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bool changed = true;
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const ZoneList<HBasicBlock*>* blocks = graph()->blocks();
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while (changed) {
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changed = false;
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for (int i = 0; i < blocks->length(); i++) {
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HBasicBlock* block = blocks->at(i);
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if (!block->IsReachable()) continue;
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bool is_reachable = blocks->at(0) == block;
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for (HPredecessorIterator it(block); !it.Done(); it.Advance()) {
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HBasicBlock* predecessor = it.Current();
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// A block is reachable if one of its predecessors is reachable,
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// doesn't deoptimize and either is known to transfer control to the
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// block or has a control flow instruction for which the next block
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// cannot be determined.
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if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) {
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HBasicBlock* pred_succ;
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bool known_pred_succ =
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predecessor->end()->KnownSuccessorBlock(&pred_succ);
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if (!known_pred_succ || pred_succ == block) {
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is_reachable = true;
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break;
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}
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}
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if (block->is_osr_entry()) {
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is_reachable = true;
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}
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}
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if (!is_reachable) {
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block->MarkUnreachable();
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changed = true;
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}
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}
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}
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}
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void HMarkUnreachableBlocksPhase::Run() {
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MarkUnreachableBlocks();
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}
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} } // namespace v8::internal
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