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Re: trouble emilinating redundant compares


On Mon, 16 Jan 2012, Paul S wrote:
> In the port I'm working on I have used the newer CC tracking technique (i.e.
> not cc0). I have followed the directions at the top of compare-elim.c and have
> the following pattern for addhi3

> I'm clearly missing something... can anyone provide a hint ?

You're running into one of the grievances with cc0 conversion:
all the single_set users.

Don't expose the CC register as being set until after reload,
and in particular not from moves and adds, reload makes heavy
use of those.  Make a parallel with a clobber of it instead.
Then have your pattern above with "reload_completed" instead of
"" as its condition.

(Or a shorter hint, do what other non-cc0 ports do. :)

brgds, H-P


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