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Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
On Mon, Oct 15, 2012 at 10:37 AM, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
> On Mon, Oct 15, 2012 at 10:19 AM, Paolo Bonzini wrote:
>> I prefer to declare the notes invalid and drop the notes.
>
> I strongly disagree with this approach though. It destroys information
> that is correct, that we had before DF_RD_PRUNE_DEAD_DEFS, that we can
> update, and that helps with optimization.
PR54916 is a case where dropping the notes would cause a missed
optimization in cse-after-loop. With my patch to update the notes, the
optimization (CSE of a load-immediate) is retained.
Ciao!
Steven