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Re: [patch] Fix PR43464: update loop closed SSA form once copy prop is done
On 3/22/10, Sebastian Pop <sebpop@gmail.com> wrote:
> On Mon, Mar 22, 2010 at 04:52, Richard Guenther <rguenther@suse.de> wrote:
>> Simply drop the gimple_num_phi_args == 1 check from the code that
>> tries to preserve loop-closed SSA form.
>
> This change passed bootstrap and test on amd64-linux.
> As I said on the PR, this change would break both h264ref
> and gamess with -O3. See
> http://groups.google.com/group/gcc-graphite-test/browse_thread/thread/f5b0d912e90b598f
>
> And there I come back again to Steven, and reiterate:
> instead of just adding more bugs like this, why not adding
> as I proposed a call to rewrite_into_loop_closed_ssa
> that would do the right thing?
>
> Sebastian
>
Because your idea of "the right thing" is IMNSHO wrong.
You, and many people like you, need to come down out of your academic
ivory tower and start thinking about the implications of your costly
let's-add-new-passes approach to solving bugs on the usability of the
compiler for the large majority of users who don't care one tiny bit
about your fancy new niche LNO optimizations.
Or in short: cost-benefit is against you.
Ciao,
Steven