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[turbofan] Broaden checkpoint elimination on returns.

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This makes the elimination of checkpoints flowing effect-wise into nodes
having the {Return} operator more permissive. We can cut out checkpoints
even when they are not wholly owned by the return. This also alleviates
a problem where TCO no longer applies.

R=jarin@chromium.org
TEST=mjsunit/regress/regress-crbug-624747
BUG=chromium:624747

Review-Url: https://codereview.chromium.org/2118793002
Cr-Commit-Position: refs/heads/master@{#37480}
This commit is contained in:
mstarzinger 2016-07-01 06:51:51 -07:00 committed by Commit bot
parent 9c281f2407
commit a757a62bf5
2 changed files with 25 additions and 3 deletions
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6
src/compiler/checkpoint-elimination.cc
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@ -41,9 +41,9 @@ Reduction CheckpointElimination::ReduceCheckpoint(Node* node) {
Reduction CheckpointElimination::ReduceReturn(Node* node) {
DCHECK_EQ(IrOpcode::kReturn, node->opcode());
Node* effect = NodeProperties::GetEffectInput(node);
if (effect->opcode() == IrOpcode::kCheckpoint && effect->OwnedBy(node)) {
// Any checkpoint that is wholly owned by a {Return} node can never be used
// for an actual bailout and can hence be cut out of the effect chain.
if (effect->opcode() == IrOpcode::kCheckpoint) {
// Any {Return} node can never be used to insert a deoptimization point,
// hence checkpoints can be cut out of the effect chain flowing into it.
Node* replacement = NodeProperties::GetEffectInput(effect);
NodeProperties::ReplaceEffectInput(node, replacement);
return Changed(node);

22
test/mjsunit/regress/regress-crbug-624747.js Normal file
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@ -0,0 +1,22 @@
// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Flags: --allow-natives-syntax --es-staging
"use strict";
function bar() {
try {
unref;
} catch (e) {
return (1 instanceof TypeError) && unref(); // Call in tail position!
}
}
function foo() {
return bar(); // Call in tail position!
}
%OptimizeFunctionOnNextCall(foo);
foo();