------- Comment #4 from rakdver at atrey dot karlin dot mff dot cuni dot cz
2006-12-13 20:22 -------
Subject: Re: gcc doesn't unroll nested loops
> Not understanding much in compiler stuff, I tried what you said, namely
> replace
> the loop with
>
> for( int i = 0; i < 3; i++ )
> for( int j = 0; j < 3; j++ )
> {
> bool a = (i == j);
> (*this)(i, j) = a * factor;
> }
>
> and compile with -O3 -funroll-loops, and toto ran in 1.1 seconds. That's
> better
> than the original 1.9 seconds, but still far from the 0.3 seconds I get
> manually unrolling the loop.
>
> Do you think there is a chance to have this bug fixed in 4.2.x or 4.3.x ?
most likely not in 4.2. I think something could be done in 4.3 timeframe.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30201
