[Sbcl-devel] FIXNUMP

[Christophe R. <cs...@ca...>]

Hi,

I happened to look in on a build that was chugging along, and saw a
note that struck me as odd:

; note: doing signed word to integer coercion (cost 20), for:
;       the first argument of FIXNUMP

This is weird because FIXNUMP is basically what is needed to see
whether a signed word to integer coercion is necessary; this note is
clearly unnecessary work.  I boiled it down to 

  (defun bar (x) 
    (declare (type (signed-byte #.sb-vm:n-word-bits) x) 
             (optimize speed))
    (sb-int:fixnump (mod -2 x)))

and indeed this indicates unneccesary work.  I think fixing this just
means implementing fixnump and check-fixnum vops for signed-num
arguments, for all platforms, but before I think about doing that,
have I missed something?

Cheers,

Christophe