/*
 * Copyright (c) 2017, 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.  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
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package org.openjdk.gcbench.runtime.cmp;

import org.openjdk.jmh.annotations.*;

import java.util.Random;
import java.util.concurrent.TimeUnit;

@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Fork(value = 10, jvmArgsAppend = {"-Xmx2g", "-Xms2g", "-XX:-TieredCompilation"})
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@Threads(1)
@State(Scope.Thread)
public class ACmpBarriersRandom {

    @Param("10000")
    private int size;

    Object[] targets;

    @Setup(Level.Iteration)
    public void setup() {
        Object[] cases = new Object[] {new Object(), new Object(), null};
        targets = new Object[size];

        Random r = new Random();
        for (int c = 0; c < size; c++) {
            targets[c] = cases[r.nextInt(cases.length)];
        }
    }

    @Benchmark
    public void test() {
        Object[] targets = this.targets;
        for (int c = 0; c < size - 1; c++) {
            acmp(targets[c], targets[c+1]);
        }
    }

    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    private boolean acmp(Object t1, Object t2) {
        return t1 == t2;
    }


    /*
        i7 4790K, 4.0 Ghz, Linux x86_64, JDK 9 (Shenandoah, 2016-09-05)

            Benchmark                (size)  Mode  Cnt   Score   Error  Units

            # Shenandoah
            ACmpBarriersRandom.test   10000  avgt   50  81.733 ± 0.237  us/op

            # G1
            ACmpBarriersRandom.test   10000  avgt   50  33.487 ± 0.082  us/op

            # Parallel
            ACmpBarriersRandom.test   10000  avgt   50  33.461 ± 0.049  us/op

        The difference is explained by a more complicated acmp barrier that needs
        to handle false negatives caused by concurrent evacuation.

        Parallel and G1:

                          [Verified Entry Point]
          2.62%    3.27%    0x00007f03c5af48c0: sub    $0x18,%rsp
          5.92%    5.57%    0x00007f03c5af48c7: mov    %rbp,0x10(%rsp)
          1.39%    1.64%    0x00007f03c5af48cc: xor    %r10d,%r10d
          1.67%    1.54%    0x00007f03c5af48cf: mov    $0x1,%eax
          4.45%    5.35%    0x00007f03c5af48d4: cmp    %rcx,%rdx         ; compare
          0.68%    1.07%    0x00007f03c5af48d7: cmovne %r10d,%eax        ; choose 0 or 1
          3.11%    3.15%    0x00007f03c5af48db: add    $0x10,%rsp
          4.07%    6.03%    0x00007f03c5af48df: pop    %rbp
          1.06%    1.66%    0x00007f03c5af48e0: test   %eax,0x1326a71a(%rip)
          1.30%    1.22%    0x00007f03c5af48e6: retq

        Shenandoah:

                               [Verified Entry Point]
          3.24%    1.91%         0x00007f11fd2addc0: sub    $0x18,%rsp
          0.35%    1.02%         0x00007f11fd2addc7: mov    %rbp,0x10(%rsp)
          0.12%    0.13%         0x00007f11fd2addcc: cmp    %rcx,%rdx           ; compare
                          ╭      0x00007f11fd2addcf: je     0x00007f11fd2adde3
          2.79%    2.58%  │      0x00007f11fd2addd1: test   %rcx,%rcx           ; null check t1
                          │╭     0x00007f11fd2addd4: je     0x00007f11fd2addfe
          1.74%    2.39%  ││     0x00007f11fd2addd6: mov    -0x8(%rcx),%rcx     ; read barrier t1
          5.90%    8.70%  ││ ↗   0x00007f11fd2addda: test   %rdx,%rdx           ; null check t2
                          ││╭│   0x00007f11fd2adddd: je     0x00007f11fd2ade02
          0.25%    0.43%  ││││   0x00007f11fd2adddf: mov    -0x8(%rdx),%rdx     ; read barrier t2
          7.54%    8.56%  ↘│││↗  0x00007f11fd2adde3: xor    %r11d,%r11d         ; same as Parallel/G1:
          1.02%    1.02%   ││││  0x00007f11fd2adde6: mov    $0x1,%eax
          4.91%    8.30%   ││││  0x00007f11fd2addeb: cmp    %rcx,%rdx           ; <--- redundant compare for the "==" path, can reuse the first one
          1.50%    2.22%   ││││  0x00007f11fd2addee: cmovne %r11d,%eax          ; choose 0 or 1
          5.38%    9.70%   ││││  0x00007f11fd2addf2: add    $0x10,%rsp
          0.47%    0.47%   ││││  0x00007f11fd2addf6: pop    %rbp
          5.10%    5.67%   ││││  0x00007f11fd2addf7: test   %eax,0x11df7203(%rip)
          1.00%    0.69%   ││││  0x00007f11fd2addfd: retq
          1.79%    2.44%   ↘│││  0x00007f11fd2addfe: xor    %ecx,%ecx           ; <--- redundant branch, can reuse %rcx above, proven to be zero
          0.50%    0.54%    │╰│  0x00007f11fd2ade00: jmp    0x00007f11fd2addda
          0.02%    0.05%    ↘ │  0x00007f11fd2ade02: xor    %edx,%edx           ; <--- redundant branch, can reuse %rdx above, proven to be zero
          0.48%    0.43%      ╰  0x00007f11fd2ade04: jmp    0x00007f11fd2adde3
     */


}