Currently, gnulib converts "inline" to "static" on OS X. In particular,
config.h uses this logic from m4/extern-inline.m4:

#if ((__GNUC__ \
      ? defined __GNUC_STDC_INLINE__ && __GNUC_STDC_INLINE__ \
      : (199901L <= __STDC_VERSION__ \
         && !defined __HP_cc \
         && !(defined __SUNPRO_C && __STDC__))) \
     && !defined __APPLE__)
...
#elif (2 < __GNUC__ + (7 <= __GNUC_MINOR__) && !defined __STRICT_ANSI__ \
       && !defined __APPLE__)
...
#else
# define _GL_INLINE static _GL_UNUSED
# define _GL_EXTERN_INLINE static _GL_UNUSED
#endif

Using "static" for "inline" comes at a tremendous cost in performance.
Compiling with gcc 4.2.1 -O2, Emacs HEAD takes 113.9 seconds to
font-lock-fontify-buffer lisp.h ten times. If I replace "!defined
__APPLE__" with "1" above, Emacs compiles and runs perfectly well
(albeit with some warnings about missing declarations) and performs the
same task in only 36.8 seconds. Disassembly confirms that in the current
configuration, nothing is actually being inlined.

Can we please remove these "!defined __APPLE__" tests and start inlining
functions again in OS X?