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8321278: C2: Partial peeling fails with assert "last_peel <- first_no…
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…t_peeled"

Reviewed-by: chagedorn, thartmann
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rwestrel committed Mar 25, 2024
1 parent 142c311 commit af15c68
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28 changes: 27 additions & 1 deletion src/hotspot/share/opto/domgraph.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -384,6 +384,25 @@ struct NTarjan {
#endif
};

void remove_single_entry_region(NTarjan* t, NTarjan*& tdom, Node*& dom, PhaseIterGVN& igvn) {
// remove phis:
for (DUIterator_Fast jmax, j = dom->fast_outs(jmax); j < jmax; j++) {
Node* use = dom->fast_out(j);
if (use->is_Phi()) {
igvn.replace_node(use, use->in(1));
--j; --jmax;
}
}
// Disconnect region from dominator tree
assert(dom->unique_ctrl_out() == t->_control, "expect a single dominated node");
tdom = tdom->_dom;
t->_dom = tdom;
assert(tdom->_control == dom->in(1), "dominator of region with single input should be that input");
// and remove it
igvn.replace_node(dom, dom->in(1));
dom = tdom->_control;
}

// Compute the dominator tree of the sea of nodes. This version walks all CFG
// nodes (using the is_CFG() call) and places them in a dominator tree. Thus,
// it needs a count of the CFG nodes for the mapping table. This is the
Expand Down Expand Up @@ -486,7 +505,14 @@ void PhaseIdealLoop::Dominators() {
assert(t->_control != nullptr,"Bad DFS walk");
NTarjan *tdom = t->_dom; // Handy access to immediate dominator
if( tdom ) { // Root has no immediate dominator
_idom[t->_control->_idx] = tdom->_control; // Set immediate dominator
Node* dom = tdom->_control;
// The code that removes unreachable loops above could have left a region with a single input. Remove it. Do it
// now that we iterate over cfg nodes for the last time (doing it earlier would have left a dead cfg node behind
// that code that goes over the dfs list would have had to handle).
if (dom != C->root() && dom->is_Region() && dom->req() == 2) {
remove_single_entry_region(t, tdom, dom, _igvn);
}
_idom[t->_control->_idx] = dom; // Set immediate dominator
t->_dom_next = tdom->_dom_child; // Make me a sibling of parent's child
tdom->_dom_child = t; // Make me a child of my parent
} else
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
/*
* Copyright (c) 2024, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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 8321278
* @summary C2: Partial peeling fails with assert "last_peel <- first_not_peeled"
* @run main/othervm -XX:CompileCommand=quiet -XX:CompileCommand=compileonly,TestPartialPeelingAtSingleInputRegion::test
* -XX:-TieredCompilation -Xbatch -XX:PerMethodTrapLimit=0 TestPartialPeelingAtSingleInputRegion
*
*/

public class TestPartialPeelingAtSingleInputRegion {

static void test() {
for (int i = 100; i > 10; --i) {
for (int j = i; j < 10; ++j) {
switch (j) {
case 1:
if (j != 0) {
return;
}
}
}
}
}

public static void main(String[] args) {
for (int i = 0; i < 10_000; ++i) {
test();
}
}
}

3 comments on commit af15c68

@openjdk-notifier
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@TheRealMDoerr
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/backport jdk21u-dev

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@openjdk openjdk bot commented on af15c68 Jun 13, 2024

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@TheRealMDoerr the backport was successfully created on the branch backport-TheRealMDoerr-af15c68f-master in my personal fork of openjdk/jdk21u-dev. To create a pull request with this backport targeting openjdk/jdk21u-dev:master, just click the following link:

➡️ Create pull request

The title of the pull request is automatically filled in correctly and below you find a suggestion for the pull request body:

Hi all,

This pull request contains a backport of commit af15c68f from the openjdk/jdk repository.

The commit being backported was authored by Roland Westrelin on 25 Mar 2024 and was reviewed by Christian Hagedorn and Tobias Hartmann.

Thanks!

If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk21u-dev:

$ git fetch https://github.com/openjdk-bots/jdk21u-dev.git backport-TheRealMDoerr-af15c68f-master:backport-TheRealMDoerr-af15c68f-master
$ git checkout backport-TheRealMDoerr-af15c68f-master
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk21u-dev.git backport-TheRealMDoerr-af15c68f-master

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