On 23/12/2010 17:09, joerg.schill...@fokus.fraunhofer.de wrote:
Darren J Moffat<darren.mof...@oracle.com> wrote:
On 22/12/2010 20:27, Garrett D'Amore wrote:
That said, some operations -- and cryptographic ones in particular --
may use floating point registers and operations because for some
architectures (sun4u rings a bell) this can make certain expensive
Well remembered! There are sun4u optimisations that use the floating
point unit but those only apply to the bignum code which in kernel is
only used by RSA.
It may be a guess caused by the fact that integer division and multiplication
is inside the FPU on SPARC processors.
Not a guess it is code to do big number integer arithmetic that is
optimised for sun4u to explicitly (ab)using the FPU. This isn't
guessing it is was a deliberate design choice.
Specifically this code here:
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/common/bignum/sun4u/
Note that there are separate kernel and user land variants of that.
--
Darren J Moffat
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