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SubjectRe: [PATCH] Input: alps: Drop unlikely before IS_ERR(_OR_NULL)
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On Wed, 2019-06-12 at 09:14 +0200, Pali Rohár wrote:
> On Tuesday 11 June 2019 17:59:13 Dmitry Torokhov wrote:
> > Hi Joe,
> >
> > On Wed, Jun 05, 2019 at 07:28:53PM -0700, Joe Perches wrote:
> > > On Thu, 2019-06-06 at 09:08 +0800, Kefeng Wang wrote:
> > > > On 2019/6/5 22:42, Pali Rohár wrote:
> > > > > On Wednesday 05 June 2019 22:24:28 Kefeng Wang wrote:
> > > > > > IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag,
> > > > > > so no need to do that again from its callers. Drop it.
> > > > > Hi! I already reviewed this patch and rejected it, see:
> > > > > https://patchwork.kernel.org/patch/10817475/
> > > > OK, please ignore it.
> > >
> > > I think the stated reason of better readability isn't
> > > particularly sensible as the object code produced is
> > > actually slightly larger.
> > >
> > > x86-64 defconfig (gcc 8.3.0)
> > >
> > > $ size drivers/input/mouse/alps.o*
> > > text data bss dec hex filename
> > > 29416 56 0 29472 7320 drivers/input/mouse/alps.o.new
> > > 29432 56 0 29488 7330 drivers/input/mouse/alps.o.old
> >
> > If gcc produces worse code for double unlikely, you should probably
> > report it to gcc folks, no? Or double unlikely turns into likely?
>
> Is measured size of stripped or unstripped binary? Plus with or without
> debug symbols? Double unlikely version should have more debug symbols
> and therefore also larger size.
>
> But if unstripped version with double unlikely is larger then it is for
> sure compiler bug.

defconfig so no debug symbols.

It's not necessarily a gcc bug as gcc doesn't
guarantee compiler repeatability.


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