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8334629: [BACKOUT] PhaseIdealLoop::conditional_move is too conservative

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Reviewed-by: epeter, thartmann, jkarthikeyan
This commit is contained in:
Quan Anh Mai 2024-06-25 17:10:20 +00:00
parent 7429c37e63
commit 933eababf2
3 changed files with 14 additions and 65 deletions
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19
src/hotspot/share/opto/loopopts.cpp
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@ -802,18 +802,25 @@ Node *PhaseIdealLoop::conditional_move( Node *region ) {
// Avoid duplicated float compare.
if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
// Ignore cost if CMOVE can be moved outside the loop.
if (used_inside_loop && cost >= ConditionalMoveLimit) {
return nullptr;
float infrequent_prob = PROB_UNLIKELY_MAG(3);
// Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
if (used_inside_loop) {
if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
// BlockLayoutByFrequency optimization moves infrequent branch
// from hot path. No point in CMOV'ing in such case (110 is used
// instead of 100 to take into account not exactness of float value).
if (BlockLayoutByFrequency) {
infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
}
}
// Check for highly predictable branch. No point in CMOV'ing if
// we are going to predict accurately all the time.
constexpr float infrequent_prob = PROB_UNLIKELY_MAG(2);
if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
//keep going
} else if (iff->_prob < infrequent_prob || iff->_prob > (1.0f - infrequent_prob)) {
} else if (iff->_prob < infrequent_prob ||
iff->_prob > (1.0f - infrequent_prob))
return nullptr;
}
// --------------
// Now replace all Phis with CMOV's

1
test/hotspot/jtreg/ProblemList.txt
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@ -53,6 +53,7 @@ compiler/loopopts/TestUnreachableInnerLoop.java 8288981 linux-s390x
compiler/c2/Test8004741.java 8235801 generic-all
compiler/c2/irTests/TestDuplicateBackedge.java 8318904 generic-all
compiler/c2/irTests/TestIfMinMax.java 8334816 generic-all
compiler/codecache/jmx/PoolsIndependenceTest.java 8264632 macosx-all
compiler/codecache/CheckLargePages.java 8332654 linux-x64

59
test/micro/org/openjdk/bench/vm/compiler/CMove.java
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@ -1,59 +0,0 @@
/*
* Copyright (c) 2023, 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.
*
* 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.
*/
package org.openjdk.bench.vm.compiler;
import java.util.concurrent.TimeUnit;
import java.util.random.RandomGeneratorFactory;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@State(Scope.Thread)
@Warmup(iterations = 5, time = 1)
@Measurement(iterations = 5, time = 1)
@Fork(value = 1)
public class CMove {
static final int SIZE = 1000000;
@Param({"0.003", "0.006", "0.01", "0.02", "0.03", "0.06", "0.1", "0.2", "0.3", "0.6"})
double freq;
boolean[] conds;
@Setup(Level.Iteration)
public void setup() {
var r = RandomGeneratorFactory.getDefault().create(1);
conds = new boolean[SIZE];
for (int i = 0; i < SIZE; i++) {
conds[i] = r.nextDouble() < freq;
}
}
@Benchmark
public void run(Blackhole bh) {
for (int i = 0; i < conds.length; i++) {
bh.consume(conds[i] ? 2 : 1);
}
}
}