-O2 problem / GCC 3.3.x
Bossom, John
John.Bossom@Cognos.COM
Mon Nov 15 20:53:00 GMT 2004
Read up on -fstrict-aliasing (which is on with -O2).
Try building again with -O2 -fno-strict-aliasing
(Not saying this is the problem, however, if it goes away with the -fno-strict-aliasing
then you'll know)
-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org]On
Behalf Of Beschorner Daniel
Sent: Monday, November 15, 2004 3:42 PM
To: 'gcc-help@gcc.gnu.org'
Subject: -O2 problem / GCC 3.3.x
Any idea why results differ between -O and -O2 with GCC 3.3.x/Linux??? GCC
2.95 works fine.
results:
-O 500000
-O2 300000
Thanks
Daniel
#include <stdio.h>
int A,B,C;
int i;
int Q[1];
int H(int X, int Y)
{
return X^Y^100000;
}
int main()
{
A=B=C=100000;
A+=H(B,C);
C+=H(A,B);
A+=H(B,C);
C+=H(A,B);
for (i=0;i<1;i++)
Q[i] = 0;
printf("%i\n",A);
return 0;
}
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