Messages in this thread | | | Date | Thu, 24 Jun 2004 08:05:34 -0400 | From | Jakub Jelinek <> | Subject | Re: using gcc built-ins for bitops? |
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On Thu, Jun 24, 2004 at 01:31:51PM +0200, Arjan van de Ven wrote: > On Thu, Jun 24, 2004 at 02:00:22AM -0700, Andrew Morton wrote: > > For the implementation it would be nice to have the old-style > > implementations in one header and the new-style ones in a separate header. > > That would create a bit of an all-or-nothing situation, but that should be > > OK? > > In addition I stuck those in asm-generic since they no longer are > architecture specific....
This is not going to work. Say on x86_64, __builtin_ctzl (~word) ends up __ctzdi2 (~word) call in GCC 3.4.x, which is not defined in the kernel (in 3.5 it will be bsfq). On a bunch of arches which don't have an instruction for ffz operation it will always result in a library call.
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