Auto-vectorization with gcj

Sun May 15 13:49:00 GMT 2005

Dietmar Lippold writes:
 > I tried to test auto-vectorization with the following java program:
 > 
 > public class Test {
 > private static int[] a = new int[256];
 > private static int[] b = new int[256];
 > private static int[] c = new int[256];
 > 
 > public static final void main(String[] args) {
 > for (int i = 0; i < 256; i++) {
 > b[i] = i;
 > c[i] = i;
 > }
 > for (int i = 0; i < 256; i++) {
 > a[i] = b[i] + c[i];
 > }
 > }
 > }
 > 
 > When I compile it with
 > 
 > gcj -msse2 -O2 -ftree-vectorize -ftree-vectorizer-verbose=5 -c Test.java
 > 
 > I get the following message:
 > 
 > Test.java:9: note: not vectorized: multiple exits.
 > Test.java:14: note: not vectorized: multiple exits.
 > Test.java:7: note: vectorized 0 loops in function.
 > 
 > Is it not possible to use auto-vectorization with gcj until now?
Not as far as I am aware, no. You may be the first person ever to
try it.
I don't know why the compiler believes the loops have multiple exits.
If you want to find out, it's time to start looking at dumps.
Andrew.