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  1. JDK
  2. JDK-4175732

JIT JDK-1.2fcs-J/x86 rounds FP-strict quotient of double incorrectly.

    Details

    • Subcomponent:
      jit
    • Resolved In Build:
      1.2fcs
    • CPU:
      x86
    • OS:
      other
    • Verification:
      Verified

      Description



      Name: dkC59003 Date: 09/23/98



      Sample program below divides double values in strictfp method. Rounded quotient is known
      and program compares it to the result of division. Exact result of division has mantissa
      with rounded part near ulp.

      On sol/x86 sample fails also with JIT JDK-1.2fcs-K and runs correctly under
      JDK 1.2fcsJ and K with interpreter. It also works correctly on Sun SPARC (jit/nojit).

      This bug affects the test in JCK 1.2beta4:
      lang/FP/fpl038/fpl03802m2/fpl03802m2.html

      ========================================= fpl03802m2.java

      import java.io.PrintStream;

      public class fpl03802m2 {

          public static void main(String argv[]) {
              if (! failedDiv(0x33b8897c0b8de74L, 0x43110a98868d957cL, 0x19d9db7170e4b1L, System.out))
                  System.out.println(" Pass 1.");
              if (! failedDiv(0x35bd9955b05112fL, 0x433bd57312e928c7L, 0x10026057f77385L, System.out))
                  System.out.println(" Pass 2.");
              if (! failedDiv(0x3445cfb2d8a649cL, 0x94ec210fc614bL, 0x433180998ecb9031L, System.out))
                  System.out.println(" Pass 3.");
          }

          static strictfp boolean failedDiv(long iX0, long iY0, long iQ0, PrintStream out) {
              double Y,X,Q;
              X = Double.longBitsToDouble(iX0);
              Y = Double.longBitsToDouble(iY0);
              Q = Double.longBitsToDouble(iQ0);
              if ( (X / Y) != Q ) {
                  final long twoM = ((long)1)<<53;
                  double diff2m = ((X / Y) * twoM) - (Q * twoM);
                  out.println(" Diff*2^m is " +diff2m +" for " +X +" / " +Y +" from waited " +Q);
                  out.println(" diff2m=" +show(diff2m) +" , X=" +show(X) +" , Y=" +show(Y)
                                      +" , Q=" +show(Q) );
                  return true;
              }
              return false;
          }

          static String show( double r ) {
              return ("0x"+Long.toHexString(Double.doubleToLongBits(r))+"L");
          }
      }

      ========================================= log
      ___ jax86 J NOne
      Warning: JIT compiler "NOne" not found. Will use interpreter.
      java version "1.2fcs"
      Classic VM (build JDK-1.2fcs-J, green threads, nojit)
      Warning: JIT compiler "NOne" not found. Will use interpreter.
       Pass 1.
       Pass 2.
       Pass 3.
      ___ jax86 J
      java version "1.2fcs"
      Classic VM (build JDK-1.2fcs-J, green threads, sunwjit)
       Diff*2^m is -4.450147717014403E-308 for 4.3110860111069824E-293 / 1.199181203203423E15 from waited 3.5950246714930137E-308
          diff2m=0x8020000000000000L , X=0x33b8897c0b8de74L , Y=0x43110a98868d957cL , Q=0x19d9db7170e4b1L
       Diff*2^m is -4.450147717014403E-308 for 1.7442487195572077E-292 / 7.834514586413255E15 from waited 2.2263647611073606E-308
          diff2m=0x8020000000000000L , X=0x35bd9955b05112fL , Y=0x433bd57312e928c7L , Q=0x10026057f77385L
       Diff*2^m is 9.007199254740992E15 for 6.376765081481208E-293 / 1.294387865344315E-308 from waited 4.926471618138161E15
          diff2m=0x4340000000000000L , X=0x3445cfb2d8a649cL , Y=0x94ec210fc614bL , Q=0x433180998ecb9031L
      ___ uname -a
      SunOS novo91 5.6 Generic i86pc i386 i86pc

      =========================================

      ======================================================================

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              • Assignee:
                never Tom Rodriguez
                Reporter:
                dkhukhrosunw Dmitry Khukhro (Inactive)
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                • Created:
                  Updated:
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