jdk/test/hotspot/jtreg/compiler/c2/TestMultiplyHighLowFusion.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test
 * @bug 8379327
 * @summary Verify correctness for combined low/high 64-bit multiplication patterns.
 * @run main/othervm -Xbatch -XX:-TieredCompilation -XX:CompileThreshold=100
 *   -XX:CompileCommand=compileonly,compiler.c2.TestMultiplyHighLowFusion::doMath
 *   -XX:CompileCommand=compileonly,compiler.c2.TestMultiplyHighLowFusion::doMathSwapped
 *   -XX:CompileCommand=compileonly,compiler.c2.TestMultiplyHighLowFusion::doUnsignedMath
 *   -XX:CompileCommand=compileonly,compiler.c2.TestMultiplyHighLowFusion::doUnsignedMathSwapped
 *   compiler.c2.TestMultiplyHighLowFusion
 */

package compiler.c2;

import java.math.BigInteger;
import java.util.Random;

public class TestMultiplyHighLowFusion {
  private static final BigInteger MASK_64 = BigInteger.ONE.shiftLeft(64).subtract(BigInteger.ONE);
  private static final long[] CORNER_CASES = {
      0L,
      1L,
      -1L,
      Long.MIN_VALUE,
      Long.MAX_VALUE,
      0x00000000FFFFFFFFL,
      0xFFFFFFFF00000000L,
      0x123456789ABCDEFL,
      0xFEDCBA9876543210L
  };

  private static long doMath(long a, long b) {
    long low = a * b;
    long high = Math.multiplyHigh(a, b);
    return low + high;
  }

  private static long doMathSwapped(long a, long b) {
    long low = b * a;
    long high = Math.multiplyHigh(b, a);
    return low + high;
  }

  private static long doUnsignedMath(long a, long b) {
    long low = a * b;
    long high = Math.unsignedMultiplyHigh(a, b);
    return low + high;
  }

  private static long doUnsignedMathSwapped(long a, long b) {
    long low = b * a;
    long high = Math.unsignedMultiplyHigh(b, a);
    return low + high;
  }

  private static long expectedSigned(long a, long b) {
    BigInteger product = BigInteger.valueOf(a).multiply(BigInteger.valueOf(b));
    long low = product.longValue();
    long high = product.shiftRight(64).longValue();
    return low + high;
  }

  private static long expectedUnsigned(long a, long b) {
    BigInteger ua = BigInteger.valueOf(a).and(MASK_64);
    BigInteger ub = BigInteger.valueOf(b).and(MASK_64);
    BigInteger product = ua.multiply(ub);
    long low = product.longValue();
    long high = product.shiftRight(64).longValue();
    return low + high;
  }

  private static void verifyPair(long a, long b) {
    long expectedSigned = expectedSigned(a, b);
    long expectedUnsigned = expectedUnsigned(a, b);

    long signed = doMath(a, b);
    long signedSwapped = doMathSwapped(a, b);
    long unsigned = doUnsignedMath(a, b);
    long unsignedSwapped = doUnsignedMathSwapped(a, b);

    if (signed != expectedSigned || signedSwapped != expectedSigned) {
      throw new RuntimeException("Signed mismatch for a=" + a + ", b=" + b +
          ": got=" + signed + ", gotSwapped=" + signedSwapped + ", expected=" + expectedSigned);
    }
    if (unsigned != expectedUnsigned || unsignedSwapped != expectedUnsigned) {
      throw new RuntimeException("Unsigned mismatch for a=" + a + ", b=" + b +
          ": got=" + unsigned + ", gotSwapped=" + unsignedSwapped + ", expected=" + expectedUnsigned);
    }
  }

  public static void main(String[] args) {
    Random random = new Random(0x8379327L);

    for (long a : CORNER_CASES) {
      for (long b : CORNER_CASES) {
        verifyPair(a, b);
      }
    }

    for (int i = 0; i < 200_000; i++) {
      verifyPair(random.nextLong(), random.nextLong());
    }
  }
}