Re: Propagate profile counts after switch case expansion (issue5896043)

[Easwaran Raman <eraman at google dot com>]

On Sun, Mar 25, 2012 at 9:40 PM, Easwaran Raman <eraman@google.com> wrote:
> On Sun, Mar 25, 2012 at 12:22 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
>>> This patch propagates execution count of thee case labels of a
>>> switch-case statement after its expansion. Bootstraps and all
>>> tests pass. OK for trunk?
>>
>> Hi,
>> while this is resonable thing to do, I belive it would make most sense
>> to make switch lowering at gimple level: i.e. reorganize the existing
>> code to produce gimple statement and change expansion code to produce
>> tablejump from every gimple switch statement that was left in the
>> code.
>>
>> This would be both cleaner and would allow gimple optimizers to improve the
>> generated code. Incrementally it would also allow us to improve switch exansion
>> that is quite baroque and not realy producing very good code in some common
>> cases.
>>
>> If you would be interested working on this (i.e. reorganizing the expansion
>> code to produce gimple), I would be very happy. If not, I can review the
>> profile updating part for mainline, since in any case this is desriable thing
>> to do.
>
> I am planning to explore improvements to switch expansion (peeling
> some cases and using jump tables for the rest, for example) and I
> think the reorganization you suggest is the right way to do such
> improvements. But until I can spend time on it and get it done, I
> would like this patch to get reviewed and checked in.
>
> Thanks,
> Easwaran

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