Definitely a +1 from me, a haven't recently seen much of a difference either.

Said that I do sometimes use it in a micro-benchmark just to convince myself we 
don't lose much performance on the checks. Usually it turns out fine, I'm happy 
and move on. But I guess there's some value in being able to elide a lot of 
checks just to see how much of a difference it does. And if there's a big 
difference then I'd try to optimise the program and elide unnecessary checks 
myself. Clearly -Ounchecked should never be used in any real code but I find 
having a baseline when optimising performance very helpful and -Ounchecked 
sometimes seemed like a cheap, automatic baseline for some code ;).

And lastly I always thought having it as an 'optimisation' is a misnomer, it's 
not an optimisation as it clearly changes the semantics of the program quite a 
bit. I thought '-unsafe-remove-checks' or something describes it better, a bit 
like '-assume-single-threaded'. But probably the 'no checks' mode adds too much 
complexity to just keep it around for a questionable way to do performance 
baselines.

> On 2 Nov 2017, at 9:52 am, Erik Eckstein via swift-dev <swift-dev@swift.org> 
> wrote:
> 
> Hi,
> 
> I’d like to propose to deprecate the -Ounchecked swift optimization mode.
> 
> The -Ounchecked mode actually contradicts one of the main goals of swift: to 
> be a safe language.
> In the past we didn’t see lot of significant performance differences compared 
> to -O (there were some improvements but also some regressions).
> Also, we want to reduce the effort of maintaining too many different 
> optimization modes, especially because we recently added -Osize.
> 
> Deprecating would mean that we map -Ounchecked to -O.
> 
> If you have any comments or concerns, please let me know
> 
> Thanks,
> Erik
> 
> 
> 
> _______________________________________________
> swift-dev mailing list
> swift-dev@swift.org
> https://lists.swift.org/mailman/listinfo/swift-dev

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