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8266480: Implicit null check optimization does not update control of …
…hoisted memory operation

Reviewed-by: neliasso, kvn
  • Loading branch information
TobiHartmann committed May 19, 2021
1 parent 3f883e8 commit c2b50f93ac36cdfd96d3ed09ec80ee5255a10200
Showing with 64 additions and 1 deletion.
  1. +2 −1 src/hotspot/share/opto/lcm.cpp
  2. +62 −0 test/hotspot/jtreg/compiler/c2/TestImplicitNullCheckDominance.java
@@ -412,7 +412,8 @@ void PhaseCFG::implicit_null_check(Block* block, Node *proj, Node *val, int allo

// Move the control dependence if it is pinned to not-null block.
// Don't change it in other cases: NULL or dominating control.
if (best->in(0) == not_null_block->head()) {
Node* ctrl = best->in(0);
if (get_block_for_node(ctrl) == not_null_block) {
// Set it to control edge of null check.
best->set_req(0, proj->in(0)->in(0));
}
@@ -0,0 +1,62 @@
/*
* Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/

package compiler.c2;

/**
* @test
* @bug 8266480
* @summary Check correct re-wiring of control edge when hoisting a memory
* operation for an implicit null check.
* @run main/othervm -Xbatch
* compiler.c2.TestImplicitNullCheckDominance
*/
public class TestImplicitNullCheckDominance {

double dFld;
int iFld;

static void test1(TestImplicitNullCheckDominance t, double d) {
for (int i = 0; i < 100; i++) {
t.dFld = d % 42;
t.iFld = 43;
}
}

static void test2(TestImplicitNullCheckDominance t) {
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 100; j++) {
t.dFld %= 42;
t.iFld = 43;
}
}
}

public static void main(String[] args) {
TestImplicitNullCheckDominance t = new TestImplicitNullCheckDominance();
for (int i = 0; i < 50_000; ++i) {
test1(t, i);
test2(t);
}
}
}

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