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Date: Fri, 15 Mar 2019 18:47:44 +0100 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: George Spelvin <lkml@....org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Daniel Wagner <daniel.wagner@...mens.com>, Dave Chinner <dchinner@...hat.com>, Don Mullis <don.mullis@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Rasmus Villemoes <linux@...musvillemoes.dk>, Andrey Abramov <st5pub@...dex.ru> Subject: Re: [PATCH 4/5] lib/list_sort: Simplify and remove MAX_LIST_LENGTH_BITS Hi George, On Fri, Mar 15, 2019 at 5:59 PM George Spelvin <lkml@....org> wrote: > On Fri, 15 Mar 2019 at 13:57:05 +0100, Geert Uytterhoeven wrote: > > On Fri, Mar 15, 2019 at 11:23 AM George Spelvin <lkml@....org> wrote: > >> On Fri, 15 Mar 2019 at 09:20:58 +0100, Geert Uytterhoeven wrote: > >>> On Fri, Mar 15, 2019 at 5:33 AM George Spelvin <lkml@....org> wrote: > >>>> One question I should ask everyone: should "count" be 32 or 64 bits > >>>> on 64-bit machines? That would let x86 save a few REX bytes. (815 > >>>> vs. 813 byte code, if anyone cares.) > >>>> > >>>> Allegedy ARM can save a few pJ by gating the high 32 > >>>> bits of the ALU. > >>>> > >>>> Most other 64-bit processors would prefer 64-bit operations as > >>>> it saves masking operations. > > > > So just make it unsigned int, unconditionally. > > As I wrote originally (and quoted above), other 64-bit machines don't > have 32-bit operations and prefer 64-bit operations because they don't > require masking. x86 (for historical compatibiity) and ARM (for power > saving) are the ones that come to mind. > > I'm trying to present the case to spur discussion, but it realy is > a *question* I'm asking about whether to do that, not a suggestion > phrased as a question. If it's just x86_64, use size_t everywhere, and let them suffer, for not being real 64-bit ;-) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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