I've already run through all tests the solution which is slightly less displeasing to me - always use the expression that I had for '#+sb-xc-host' and remove the 
#-sb-xc-host case.  But leave the straightforward call to ash on 64-bit platform. 

On Sun, Mar 16, 2014 at 11:16 PM, Stas Boukarev <stassats@gmail.com> wrote:
Douglas Katzman <dougk@google.com> writes:

> or, better stated: shouldn't we define that function for other platforms as
> well?  I mean "couldn't" it define it for others, not "doesn't" it...
ash-left-modfx function is only defined for constant folding, it isn't
supposed to be called directly.

A lying-to-the-compiler way to get fast and working-not-only-on-x86oids
would be:
(truly-the fixnum (ash (the type-number value) (the (mod #.+infos-per-word+) position)))

With best regards, Stas.