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[crankshaft] Make infinite loops preserve control flow.

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We have to preserve control flow so that the liveness analysis is less
confused. This CL fixes loops to preserve teh original control flow.

BUG=chromium:599710
LOG=n

Review URL: https://codereview.chromium.org/1863123002

Cr-Commit-Position: refs/heads/master@{#35318}
This commit is contained in:
jarin 2016-04-06 22:36:25 -07:00 committed by Commit bot
parent ea61d86f0d
commit 3df0a8c1f2
2 changed files with 71 additions and 17 deletions
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39
src/crankshaft/hydrogen.cc
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@ -5116,7 +5116,7 @@ void HOptimizedGraphBuilder::VisitDoWhileStatement(DoWhileStatement* stmt) {
HBasicBlock* body_exit =
JoinContinue(stmt, current_block(), break_info.continue_block());
HBasicBlock* loop_successor = NULL;
if (body_exit != NULL && !stmt->cond()->ToBooleanIsTrue()) {
if (body_exit != NULL) {
set_current_block(body_exit);
loop_successor = graph()->CreateBasicBlock();
if (stmt->cond()->ToBooleanIsFalse()) {
@ -5158,19 +5158,17 @@ void HOptimizedGraphBuilder::VisitWhileStatement(WhileStatement* stmt) {
// If the condition is constant true, do not generate a branch.
HBasicBlock* loop_successor = NULL;
if (!stmt->cond()->ToBooleanIsTrue()) {
HBasicBlock* body_entry = graph()->CreateBasicBlock();
loop_successor = graph()->CreateBasicBlock();
CHECK_BAILOUT(VisitForControl(stmt->cond(), body_entry, loop_successor));
if (body_entry->HasPredecessor()) {
body_entry->SetJoinId(stmt->BodyId());
set_current_block(body_entry);
}
if (loop_successor->HasPredecessor()) {
loop_successor->SetJoinId(stmt->ExitId());
} else {
loop_successor = NULL;
}
HBasicBlock* body_entry = graph()->CreateBasicBlock();
loop_successor = graph()->CreateBasicBlock();
CHECK_BAILOUT(VisitForControl(stmt->cond(), body_entry, loop_successor));
if (body_entry->HasPredecessor()) {
body_entry->SetJoinId(stmt->BodyId());
set_current_block(body_entry);
}
if (loop_successor->HasPredecessor()) {
loop_successor->SetJoinId(stmt->ExitId());
} else {
loop_successor = NULL;
}
BreakAndContinueInfo break_info(stmt, scope());
@ -5199,10 +5197,9 @@ void HOptimizedGraphBuilder::VisitForStatement(ForStatement* stmt) {
DCHECK(current_block() != NULL);
HBasicBlock* loop_entry = BuildLoopEntry(stmt);
HBasicBlock* loop_successor = NULL;
HBasicBlock* loop_successor = graph()->CreateBasicBlock();
HBasicBlock* body_entry = graph()->CreateBasicBlock();
if (stmt->cond() != NULL) {
HBasicBlock* body_entry = graph()->CreateBasicBlock();
loop_successor = graph()->CreateBasicBlock();
CHECK_BAILOUT(VisitForControl(stmt->cond(), body_entry, loop_successor));
if (body_entry->HasPredecessor()) {
body_entry->SetJoinId(stmt->BodyId());
@ -5213,6 +5210,14 @@ void HOptimizedGraphBuilder::VisitForStatement(ForStatement* stmt) {
} else {
loop_successor = NULL;
}
} else {
// Create dummy control flow so that variable liveness analysis
// produces teh correct result.
HControlInstruction* branch = New<HBranch>(graph()->GetConstantTrue());
branch->SetSuccessorAt(0, body_entry);
branch->SetSuccessorAt(1, loop_successor);
FinishCurrentBlock(branch);
set_current_block(body_entry);
}
BreakAndContinueInfo break_info(stmt, scope());

49
test/mjsunit/regress/regress-599710.js Normal file
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@ -0,0 +1,49 @@
// 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
var f1 = function() { while (1) { } }
function g1() {
var s = "hey";
f1 = function() { return true; }
if (f1()) { return s; }
}
%OptimizeFunctionOnNextCall(g1);
assertEquals("hey", g1());
var f2 = function() { do { } while (1); }
function g2() {
var s = "hey";
f2 = function() { return true; }
if (f2()) { return s; }
}
%OptimizeFunctionOnNextCall(g2);
assertEquals("hey", g2());
var f3 = function() { for (;;); }
function g3() {
var s = "hey";
f3 = function() { return true; }
if (f3()) { return s; }
}
%OptimizeFunctionOnNextCall(g3);
assertEquals("hey", g3());
var f4 = function() { for (;;); }
function g4() {
var s = "hey";
f4 = function() { return true; }
while (f4()) { return s; }
}
%OptimizeFunctionOnNextCall(g4);
assertEquals("hey", g4());