Re: Shrinking the C core

[Emanuel Berg]

Alfred M. Szmidt wrote:

>> For example, when I write
>>
>> (when (> x y) (when (> x y) x))
>>
>> I expect GCC JIT to throw away the duplicate comparison.
>
> Why do you expect that? Why do you think it is duplicate?
> Where are the guarantees that > or WHEN don't have
> side-effects? Do you know the exact type of X and Y so you
> can skip a cascade of type checks to pick the right
> comparison operator? Can you use fixnum comparison of
> a specific bit width? Do you need to use bignum comparison?
>
> That is the type of information SBCL knows about, or allows
> the user to specify. Emacs does not have that today [...]

Why can SBCL answer those questions based on the sample code,
and not Emacs? What is it that they have, and we don't?
And why can't we have it as well?

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