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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>, David Woodhouse
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Date: Fri, 22 Jul 2016 10:17:38 -0700
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Subject: Re: [Ksummit-discuss] [TECH TOPIC] Compiler shopping list
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On Fri, 2016-07-22 at 19:05 +0200, Christian Borntraeger wrote:
> On 07/22/2016 05:59 PM, David Woodhouse wrote:
> > On Fri, 2016-07-22 at 17:52 +0200, Christian Borntraeger wrote:
> > > On 07/22/2016 12:41 PM, David Howells wrote:
> > > > Are there additional things we can get the compiler to do for 
> > > > us?  Some things I've seen brought up:
> > > > 
> > > >  (1) Additional __atomic_*() ops could be useful.  Suggestions 
> > > > I've heard      include direct LL/SC support - though the 
> > > > compiler people don't seem so keen on that.
> > > > 
> > > >  (2) -mmodel=kernel flag so that the compiler can optimise 
> > > > better for the kernel memory model.
> > > 
> > > Some years ago (actually many) Linus proposed to have an 
> > > endianess attribute to data types, so that the compiler can do 
> > > the bswap automatically. For some reason this was never
> > > implemented, but this might be a good idea anyway.
> > > 
> > > e.g. 
> > > 
> > > unsigned long x[10] __attribute__(("bigendian"));
> > 
> > I'm not sure Linus proposed that. I certainly did, many times.
> 
> Yes, I know at least 3 people suggesting that and thinking this is 
> useful ( Can you beat Linus' 2001 
> https://gcc.gnu.org/ml/gcc/2001-12/msg00932.html? ;-) )

The fact that it's been discussed on and off for 15 years tends to
suggest that where we've ended up is about good enough for everyday and
no-one can really be bothered to take the extra effort.

So what's the overriding reason we should spend the extra effort now?

James