[lld] r233088 - [Mips] Suppress "right shift by too large amount" warning

[David Blaikie]

Started a thread on llvmdev to discuss the prinicples here.

On Wed, Mar 25, 2015 at 11:56 AM, Aaron Ballman <aaron at aaronballman.com>
wrote:

> On Wed, Mar 25, 2015 at 2:02 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> > On Wed, Mar 25, 2015 at 10:55 AM, Simon Atanasyan <simon at atanasyan.com>
> > wrote:
> >>
> >> On Wed, Mar 25, 2015 at 8:42 PM, David Blaikie <dblaikie at gmail.com>
> wrote:
> >> >
> >> > On Wed, Mar 25, 2015 at 10:38 AM, Simon Atanasyan <
> simon at atanasyan.com>
> >> > wrote:
> >> >>
> >> >> By the way, what do you suggest to silence the VC++ warning?
> >> >
> >> > Disabling the warning, this is a false positive because some
> >> > instantiations
> >> > of the template produce non-zero results out of this shift and the
> fact
> >> > that
> >> > some other instantiations always produce 0 is fine. Same goes for
> >> > template-conditionally dead code, etc.
> >>
> >> In fact I am satisfied by the current code as well as by you
> >> suggestion. The only problem - I do not have access to VC++ so cannot
> >> surround the code by appropriate warning disabling pragmas and check
> >> that they work.
> >
> >
> > Nah, I'm suggesting a somewhat more aggressive patth forward: disable the
> > warning entirely for the LLVM build. Andy Kaylor recently submitted a
> patch
> > to disable a bunch of noisy MSVC warnings & I'd suggest we just add this
> one
> > to the list.
>
> I'm still somewhat opposed to that idea. This warning does find true
> positives (though infrequently, I would imagine). We do a fair amount
> of bit twiddling in our code base (including in ADT classes), and
> turning off this warning because of one false-positive for which we've
> found several ways to silence it seems extreme. This isn't a
> particularly chatty diagnostic, and it's almost always going to point
> out a code smell that we would want to look at further when it does
> arise.
>
> ~Aaron
>
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