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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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,
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 *
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package org.openjdk;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;

import java.util.concurrent.TimeUnit;

@State(Scope.Thread)
@Fork(1)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
public class BooleanNegate {

    /*
      Credits are due to Henrik Johansson (https://twitter.com/dahankzter) for pointing this out.

      Trying to disprove the PMD rule:
        http://pmd.sourceforge.net/pmd-5.2.1/pmd-java/rules/java/controversial.html#BooleanInversion

      The rule is inspired by Dr. Heinz Kabutz article here:
        http://www.javaspecialists.eu/archive/Issue042.html

      However, this benchmark running on i7-4790K, JDK 8u40-ea, Linux x86_64 yields:
         Benchmark                           Mode  Samples  Score   Error  Units
         o.o.BooleanNegate.assignBitwise     avgt        5  1.516 ± 0.024  ns/op
         o.o.BooleanNegate.assignNegation    avgt        5  1.515 ± 0.009  ns/op
         o.o.BooleanNegate.assignTernary     avgt        5  1.513 ± 0.014  ns/op
         o.o.BooleanNegate.baseline          avgt        5  0.630 ± 0.010  ns/op

      All three tests are yielding the same score, because they are generated as the same
      instruction sequence, see below. All use "xor $x, 1" to negate the boolean value.
      If there is a JDK which has either of three tests faster/slower, that's a
      code generation performance bug.
     */

    private boolean x = true;

    @Benchmark
    public boolean baseline() {
        return x;
    }

    /*
      0x00007f2555191212: movzbl 0x94(%rdi),%r10d
      0x00007f255519121a: add    $0x1,%rbp
      0x00007f255519121e: test   %eax,0x173f4ddc(%rip)
      0x00007f2555191224: test   %r10d,%r10d
      0x00007f2555191227: jne    0x00007f25551911e0
      0x00007f2555191229: movzbl 0xd2(%rcx),%r10d
      0x00007f2555191231: movzbl 0xc(%r11),%edx        ; get $x
      0x00007f2555191236: xor    $0x1,%edx             ; BOOLEAN NEGATE
      0x00007f2555191239: mov    %dl,0xc(%r11)         ; store $x
      0x00007f255519123d: movzbl 0xd3(%rcx),%r8d
      0x00007f2555191245: cmp    %r8d,%edx
      0x00007f2555191248: jne    0x00007f2555191212
      0x00007f255519124a: cmp    %r10d,%edx
      0x00007f255519124d: mov    $0x1,%r8d
      0x00007f2555191253: cmovne %r9d,%r8d
      0x00007f2555191257: test   %r8d,%r8d
      0x00007f255519125a: je     0x00007f2555191212
     */

    @Benchmark
    public boolean assignNegation() {
        x = !x;
        return x;
    }

    /*
      0x00007f84dd192a80: movzbl 0x94(%rdx),%r10d
      0x00007f84dd192a88: add    $0x1,%rbp
      0x00007f84dd192a8c: test   %eax,0x1777956e(%rip)
      0x00007f84dd192a92: test   %r10d,%r10d
      0x00007f84dd192a95: jne    0x00007f84dd192a47
      0x00007f84dd192a97: movzbl 0xd2(%rcx),%r10d
      0x00007f84dd192a9f: movzbl 0xc(%r11),%edi      ; get $x
      0x00007f84dd192aa4: xor    $0x1,%edi           ; BOOLEAN NEGATE
      0x00007f84dd192aa7: mov    %dil,0xc(%r11)      ; store $x
      0x00007f84dd192aab: movzbl 0xd3(%rcx),%r8d
      0x00007f84dd192ab3: cmp    %r8d,%edi
      0x00007f84dd192ab6: jne    0x00007f84dd192a80
      0x00007f84dd192ab8: cmp    %r10d,%edi
      0x00007f84dd192abb: mov    $0x1,%r10d
      0x00007f84dd192ac1: cmovne %r9d,%r10d
      0x00007f84dd192ac5: test   %r10d,%r10d
      0x00007f84dd192a80  je     0x00007f84dd192a80
     */

    @Benchmark
    public boolean assignBitwise() {
        x ^= true;
        return x;
    }

    /*
      0x00007feac918a152: movzbl 0x94(%rdx),%r10d
      0x00007feac918a15a: add    $0x1,%rbp
      0x00007feac918a15e: test   %eax,0x16351e9c(%rip)
      0x00007feac918a164: test   %r10d,%r10d
      0x00007feac918a167: jne    0x00007feac918a120
      0x00007feac918a169: movzbl 0xd2(%rcx),%r10d
      0x00007feac918a171: movzbl 0xc(%r11),%edi      ; get $x
      0x00007feac918a176: xor    $0x1,%edi           ; BOOLEAN NEGATE
      0x00007feac918a179: mov    %dil,0xc(%r11)      ; store $x
      0x00007feac918a17d: movzbl 0xd3(%rcx),%r8d
      0x00007feac918a185: cmp    %r8d,%edi
      0x00007feac918a188: jne    0x00007feac918a152
      0x00007feac918a18a: cmp    %r10d,%edi
      0x00007feac918a18d: mov    $0x1,%r10d
      0x00007feac918a193: cmovne %r9d,%r10d
      0x00007feac918a197: test   %r10d,%r10d
      0x00007feac918a19a: je     0x00007feac918a152
     */

    @Benchmark
    public boolean assignTernary() {
        x = x ? false : true;
        return x;
    }
}