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Re: [PATCH 8/9] ifcvt: Handle swap-style idioms differently.


Robin Dapp <rdapp@linux.ibm.com> writes:
>> Looks like a nice optimisation, but could we just test whether the
>> destination of a set isn't live on exit from the then block?  I think
>> we could do that on the fly during the main noce_convert_multiple_sets
>> loop.
>
> I included this locally along with the rest of the remarks. Any comments
> on the rest/bulk of the patch (the part trying to compare costs of both
> cmovs "types")?

I'm still a bit worried about the overlap between the expanded
noce_convert_multiple_sets and cond_move_process_if_block (5/9).
It seems like we're making noce_convert_multiple_set handle most of
the conditional move cases that cond_move_process_if_block can handle.
But like you say, noce_convert_multiple_set is still restricted to
half-diamonds, whereas cond_move_process_if_block can handle full
diamonds.

3/9, 4/9 and 8/9 seems like good independent improvements.
But for 5/9, 6/9 and 7/9, it looks to me like it would be better
to improve cond_move_process_if_block so that it handles all the
conditional move cases you're targetting.

Definitely welcome other opinions though. :-)

Thanks,
Richard


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