Messages in this thread | | | Subject | Re: [PATCH 2/5] bitops: compile time optimization for hweight_long(CONSTANT) | From | Peter Zijlstra <> | Date | Wed, 03 Feb 2010 16:47:34 +0100 |
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On Wed, 2010-02-03 at 07:42 -0800, Andrew Morton wrote: > On Wed, 03 Feb 2010 16:15:57 +0100 Peter Zijlstra <peterz@infradead.org> wrote: > > > On Wed, 2010-02-03 at 07:08 -0800, Andrew Morton wrote: > > > On Wed, 3 Feb 2010 21:39:51 +0800 Wu Fengguang <fengguang.wu@intel.com> wrote: > > > > > > > Is there an official lowest GCC version that Linux supports? > > > > > > Documentation/Changes says gcc-3.2. > > > > Anyway, its not like that macro I used isn't straight forward. Not much > > a builtin can do better. > > > > The only benefit the builtin has is possibly use machine popcnt > > instructions but we already deal with that in the kernel. > > We didn't deal with it on every architecture, which is something which > the compiler extension takes care of. > > In fact I can't find anywhere where we dealt with it on x86.
>From what I know the popcnt ins on x86 is relatively new, hpa was going to look at supporting it using alternatives.
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