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Re: Unnecessary PRE optimization
On Sat, Dec 26, 2009 at 2:07 AM, Daniel Berlin <dberlin@dberlin.org> wrote:
>> In general it will be tricky for latter passes to clean up the messes.
>> The fundamental problem is that the address computation is exposed to
>> PRE prematurely (for a given target ?) at GIMPLE level.
>
>
> Yeah, i'm not sure PRE can really do anything different here.
> I also think you would have a very hard time trying to stop everything
> from moving invariant computations around at the tree level.
> Might make more sense to finish the tree level with a global code
> motion pass that is target sensitive or something.
And you also need to deal with the case where the address computation
is already commoned in the original source. Btw, a optimization option
to trigger fwprop and initializing it differently for different targets would
work for me as a temporary workaround (not that this address cost issue
is new ...)
Richard.