8257575: C2: "failed: only phis" assert failure in loop strip mining verification
Reviewed-by: thartmann, neliasso
diff --git a/src/hotspot/share/opto/loopnode.cpp b/src/hotspot/share/opto/loopnode.cpp
index 0ed4943..66c63f4 100644
--- a/src/hotspot/share/opto/loopnode.cpp
+++ b/src/hotspot/share/opto/loopnode.cpp
@@ -1792,12 +1792,28 @@
} 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 @@
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");
diff --git a/test/hotspot/jtreg/compiler/loopstripmining/TestEliminatedLoadPinnedOnBackedge.java b/test/hotspot/jtreg/compiler/loopstripmining/TestEliminatedLoadPinnedOnBackedge.java
new file mode 100644
index 0000000..cf31102
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/loopstripmining/TestEliminatedLoadPinnedOnBackedge.java
@@ -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);
+ }
+}
