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Re: [Bug tree-optimization/21712] missed optimization due withconst function and pulling out of loops
On Sun, 2005-05-22 at 21:13 +0000, rakdver at atrey dot karlin dot mff
dot cuni dot cz wrote:
> ------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni dot cz 2005-05-22 21:13 -------
> Subject: Re: missed optimization due with const function and pulling out of loops
>
> > > Nevertheless, even if we are very strict with the definition, moving
> > > get_type2 out of the loop is not a good idea, since get_type2 might
> > > potentially be very expensive (and we have no way how to determine
> > > that this is not the case), thus we would lose in case get_type2
> > > should be never executed.
> > >
> > >
> >
> > Don't we attempt to detect zero trip loops?
> > (If not, we should :P)
>
> I don't see how this is relevant to the PR.
>
Uh, you claimed we won't move get_type2 out, even if it is const,
becuase it might not normally execute.
If we can't prove we don't execute the loop, you should move it out.
Otherwise, your logic would hold for get_type1 just the same, which we
*do* move out of the loop.
IOW, there is no reason to move get_type1 out but not get_type2
>