Messages in this thread | | | Date | Thu, 24 Jun 2004 14:35:16 +0200 | From | Arjan van de Ven <> | Subject | Re: using gcc built-ins for bitops? |
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On Thu, Jun 24, 2004 at 08:05:34AM -0400, Jakub Jelinek wrote: > 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.
It's actually fine; the architecture first needs to include this file and there it can use the proper ifdefs; the functions themselves don't matter, only when they can be used, and the arch still controls that.
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