Re: bug in gcj constant folding

[Bryce McKinlay <bryce@albatross.co.nz>]

"Konstantin L. Metlov" wrote:
 
> It seems there is a bug in a constant propagation (folding) code of gcj.
> Sorry if it was already reported.

I suspect this could be related to the problem I reported a few days ago to do under "gcjh and static final's". The problem is to do with the source parser - if you compile your .java file with another java compiler (jikes or javac), then compile the class files to native code with gcj, the problem does not occur.

> Unfortunately I was not able to run this test under
> latest egcs snapshot.
> Compilation of recent libgcj failed for me with
> gcj: Internal compiler error: program jc1 got fatal signal 11
> when compiling class library to bytecode (gcj -C ... a lot of .java
> files).
FYI: I'm getting this too. I might try checking out the gcc 2.95 branch
from cvs if it doesn't go away soon.
> Anyway gcj works great and runs my numerical simulation
> (physics) nearly
> twice as fast as jdk with a JIT. This is my first simulation in java
> (all
> others were in Fortran). I think java+gcj are great for numerical
> computations when no special mathematical functions are required.
A while back I ran the Sieve.java benchmark (attached) that comes
with TYA through GCJ and compared it to a few other environments:

Eratosthenes Sieve prime number benchmark in Java (P2 233Mhz)

                                 (iterations/sec)
Linux:
JDK 1.1.7A (no JIT)              76
JDK 1.1.7A (TYA 1.2v3 JIT)       248
kaffe 1.0b4                      335
JDK 1.2pre1 (Sun JIT)            494
gcj -O (w/array bounds checking) 1099
gcj -O (--no-bounds-check)       2005

Windows:
JDK 1.1.7 (NT, no JIT)           81
JDK 1.2 (NT w/JIT)               1404
JDK 1.1.7 (NT w/JIT)             1423

I've noticed that gcj compiled numerical benchmarks seem to perform faster with -O than with -O3. Strange, since I allways thought that higher numbers were supposed to increase the level of optimisation?

regards

  [ bryce ]
 

//  Eratosthenes Sieve prime number benchmark in Java

public class Sieve {

  static String results1, results2;

  public static void main(String[] args) {
     System.out.println("Running Sieve benchmark.");
     System.out.println("This will take about 10 seconds.");
     runSieve();
     System.out.println(results1);
     System.out.println(results2);
  }

  static void runSieve() {
     int SIZE = 8190;
     boolean flags[] = new boolean[SIZE+1];
     int i, prime, k, iter, count;
     int iterations = 0;
     double seconds = 0.0;
     int score = 0;
     long startTime, elapsedTime;

     startTime = System.currentTimeMillis();
     while (true) {
        count=0;
        for(i=0; i<=SIZE; i++) flags[i]=true;
        for (i=0; i<=SIZE; i++) {
           if(flags[i]) {
              prime=i+i+3;
              for(k=i+prime; k<=SIZE; k+=prime)
                 flags[k]=false;
              count++;
           }
        }
        iterations++;
        elapsedTime = System.currentTimeMillis() - startTime;
        if (elapsedTime >= 10000) break;
     }
     seconds = elapsedTime / 1000.0;
     score = (int) Math.round(iterations / seconds);
     results1 = iterations + " iterations in " + seconds + " seconds";
     if (count != 1899)
        results2 = "Error: count <> 1899";
     else
        results2 = "Sieve score = " + score;
  }
}