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Re: 128-bit integer - nonsensical documentation?
- From: Jeffrey Walton <noloader at gmail dot com>
- To: Kostas Savvidis <ksavvidis at gmail dot com>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Wed, 26 Aug 2015 07:44:48 -0400
- Subject: Re: 128-bit integer - nonsensical documentation?
- Authentication-results: sourceware.org; auth=none
- References: <1B1111BE-E274-4C80-8189-22B78D77647A at gmail dot com>
- Reply-to: noloader at gmail dot com
On Wed, Aug 26, 2015 at 7:04 AM, Kostas Savvidis <ksavvidis@gmail.com> wrote:
> The online documentation contains the attached passage as part of the "C-Extensionsâ chapter. There are no actual machines which have an " integer mode wide enough to hold 128 bitsâ as the document puts it. This would be a harmless confusion if it didnât go on to say ââ long long integer less than 128 bits wideâ (???!!!) Whereas in reality "long long intâ is 64 bits everywhere i have seen.
>
On 64-bit platforms, a 128-bit integer is available. I don't know how
widespread it is, but its available on the Intel Mac I use and some of
my P4 machines.
When using OpenSSL, if you configure with enable-ec_nistp_64_gcc_128,
then Elliptic Curve Diffie-Hellman is about 2x to 4x faster. You have
to enable enable-ec_nistp_64_gcc_128 manually because OpenSSL's
configure cannot detect it. See, for example
https://wiki.openssl.org/index.php/Compilation_and_Installation.
Jeff