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Re: Making 'eq' == 'eql' in bignum branch

From: Stefan Monnier
Subject: Re: Making 'eq' == 'eql' in bignum branch
Date: Fri, 10 Aug 2018 11:55:51 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

>> NaN boxing implies 64bit boxes, which on 32bit platforms imposes
>> a non-negligible overhead.
> Sorry, I don't understand. I don't see how any of this applies to
> 32-bit platforms with 32-bit EMACS_INTs. On those, we cannot have
> float immediates or NaN boxing.

Indeed.  But we want eq == eql on all platforms, including 32bit ones.

>> So, I think it'd end up costing
>> significantly more than the tentative patch with which Paul and I have
>> been playing.
> I think we only have a benchmark for 61-bit floats, which would mean

His idea was to use "immediate floats" when possible (e.g. with 4 zero
bits) and use hash-consed boxed floats for the rest, hence preserving
full 64bit float precision.

IOW the point was to reduce the proportion of floats we need to


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