stan/jdk-24
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

8257575: C2: "failed: only phis" assert failure in loop strip mining verification

Browse Source 
Reviewed-by: thartmann, neliasso
This commit is contained in:
Roland Westrelin 2020-12-07 09:38:22 +00:00
parent d05401d886
commit f5a582c287
2 changed files with 175 additions and 1 deletions
src/hotspot/share/opto
loopnode.cpp
test/hotspot/jtreg/compiler/loopstripmining
TestEliminatedLoadPinnedOnBackedge.java

20
src/hotspot/share/opto/loopnode.cpp

@ -1792,12 +1792,28 @@ void LoopNode::verify_strip_mined(int expect_skeleton) const {
} else {
assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
uint phis = 0;
uint be_loads = 0;
Node* be = inner->in(LoopNode::LoopBackControl);
for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
Node* u = inner->fast_out(i);
if (u->is_Phi()) {
phis++;
for (DUIterator_Fast jmax, j = be->fast_outs(jmax); j < jmax; j++) {
Node* n = be->fast_out(j);
if (n->is_Load()) {
assert(n->in(0) == be, "should be on the backedge");
do {
n = n->raw_out(0);
} while (!n->is_Phi());
if (n == u) {
be_loads++;
break;
}
}
}
}
}
assert(be_loads <= phis, "wrong number phis that depends on a pinned load");
for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
Node* u = outer->fast_out(i);
assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
@ -1809,7 +1825,9 @@ void LoopNode::verify_strip_mined(int expect_skeleton) const {
stores++;
}
}
assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
// Late optimization of loads on backedge can cause Phi of outer loop to be eliminated but Phi of inner loop is
// not guaranteed to be optimized out.
assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
}
assert(sfpt->outcnt() == 1, "no data node");
assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");

156
test/hotspot/jtreg/compiler/loopstripmining/TestEliminatedLoadPinnedOnBackedge.java Normal file

@ -0,0 +1,156 @@
/*
* Copyright (c) 2020, Red Hat, Inc. 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/**
* @test
* @bug 8257575
* @summary C2: "failed: only phis" assert failure in loop strip mining verfication
*
* @run main/othervm -XX:LoopUnrollLimit=0 -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:CompileCommand=dontinline,TestEliminatedLoadPinnedOnBackedge::notInlined
* -XX:CompileCommand=inline,TestEliminatedLoadPinnedOnBackedge::inlined TestEliminatedLoadPinnedOnBackedge
*
*/
public class TestEliminatedLoadPinnedOnBackedge {
private static Object field2;
final static int iters = 2000;
public static void main(String[] args) {
boolean[] flags = new boolean[iters];
for (int i = 0; i < iters; i++) {
flags[i] = i < iters/2;
}
for (int i = 0; i < 20_000; i++) {
test1(flags);
test2(flags, 1);
test3(flags);
inlined(new Object(), 1);
inlined(new Object(), 4);
inlined2(42);
inlined2(0x42);
}
}
static int field;
private static int test1(boolean[] flags) {
int k = 2;
for (; k < 4; k *= 2) {
}
int[] array = new int[10];
notInlined(array);
// This load commons with the load on the backedge after the
// outer strip mined loop is expanded.
int v = array[0];
array[1] = 42;
// No use for o. Allocation removed at macro expansion time.
Object o = new Object();
inlined(o, k);
int i = 0;
for (; ; ) {
synchronized (array) {
}
if (i >= iters) {
break;
}
v = array[0]; // This load ends up on the backedge
if (flags[i]) {
inlined2(array[1]);
}
i++;
}
return v;
}
private static int test2(boolean[] flags, int d) {
int k = 2;
for (; k < 4; k *= 2) {
}
int[] array = new int[10];
notInlined(array);
int v = array[0];
array[1] = 42;
Object o = new Object();
inlined(o, k);
int i = 0;
for (; ; ) {
synchronized (array) {
}
if (d == 0) {}
if (i >= iters) {
break;
}
v = (array[0] + array[2]) / d;
if (flags[i]) {
inlined2(array[1]);
}
i++;
}
return v;
}
private static int test3(boolean[] flags) {
int k = 2;
for (; k < 4; k *= 2) {
}
int[] array = new int[10];
notInlined(array);
int v1 = array[0];
int v2 = array[2];
array[1] = 42;
Object o = new Object();
inlined(o, k);
int i = 0;
for (; ; ) {
synchronized (array) {
}
if (i >= iters) {
break;
}
v1 = array[0];
v2 = array[2];
if (flags[i]) {
inlined2(array[1]);
}
i++;
}
return v1 + v2;
}
private static void inlined2(int i) {
if (i != 42) {
field = 42;
}
}
private static void inlined(Object o, int i) {
if (i != 4) {
field2 = o;
}
}
private static void notInlined(int[] array) {
java.util.Arrays.fill(array, 1);
}
}