swift234

VarArgs: use "is" checking on metatypes to check for floating-point arguments on x86-64.

Previously, we were checking whether a particular argument could be
dynamic-casted to a Float or Double (via as?). However, now that
dynamic casting considers bridging, this would try to pass an NSNumber
in a floating-point register, and hilarity ensues. Fixes the
regression I introduced with object-to-value bridging in r20963.


Swift SVN r20967