[Cryptography] Speculation considered harmful?

Nico Williams nico at cryptonector.com
Wed Jan 10 11:02:50 EST 2018


On Tue, Jan 09, 2018 at 05:46:07PM -0500, Theodore Ts'o wrote:
> Yet another problem with VLIW is that the optimizations tend to be
> horribly architecture specific.  If you change the number of various
> functional units, but you want to keep the instruction set backwards
> compatibility, that's possible --- but if the compiler has to know how
> the instructions will be scheduled, not only is it slow to compile,
> but what is optimized for a particular version of Itanic might have be
> terribe performance on a different version of the Itanic.

VLIW == no stable ABI.  We'd have to ship bitcode and re-optimize,
assemble, and link for every VLIW CPU model.

It wouldn't be the end of the world.  But first we'd need the compilers
that could handle it.

Nico
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