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Re: [kill-loop] Fix a quadratic bottleneck in loop-unroll
On Friday 05 August 2005 11:43, Zdenek Dvorak wrote:
> Hello,
>
> > This patch fixes a problem with -fvariable-expansion-in-unroller. The
> > algorithm to analyze instructions was quadratic. Fixed by letting df.c
> > do the data flow beforehand. I have bootstrapped and tested this patch
> > with "-O2 -funroll{,-all}-loops -fvariable-expansion-in-unroller" on
> > x86_64-unknown-linux-gnu. Zdenek, does the patch look good to you?
>
> yes, this seems sane to me (does it mean that someone actually uses
> the -fvariable-expansion-in-unroller flag? I have always lived under
> impression that anything that is not enabled by default is not used
> by anyone and hopelessly broken :-)
Well, -fvariable-expansion-in-unroller works. It just showed up as
a major compile time problem when I tried it to see what it does :-)
I haven't checked whether the flag actually gives better performance.
Gr.
Steven