[llvm] r211254 - Convert some assert(0) to llvm_unreachable or fold an 'if' condition into the assert.

[Reid Kleckner]

On Thu, Jun 19, 2014 at 9:28 AM, Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:

>
> > On 2014-Jun-19, at 00:03, Alp Toker <alp at nuanti.com> wrote:
> >
> >
> > On 19/06/2014 09:10, Craig Topper wrote:
> >> Author: ctopper
> >> Date: Thu Jun 19 01:10:58 2014
> >> New Revision: 211254
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=211254&view=rev
> >> Log:
> >> Convert some assert(0) to llvm_unreachable or fold an 'if' condition
> into the assert.
> >
> >
> > Hi Craig,
> >
> > While working on this commit did you get a feel for whether we could get
> rid of the llvm_unreachable() string parameter?
> >
> > The llvm_unreachable("Unexpected enum value/XYZ") messages always looked
> less-than-useful to me. Unlike asserts they get used in places that are
> genuinely unreachable, even used as an optimisation hint in release builds.
> As a result the strings are seldom seen, making the small but conscious
> effort it takes to write them somewhat demeaning.
> >
> > Alp.
>
> They also get used in places that are supposed to be unreachable, but
> aren't.  When
> we get a crash, I think it's good to know why.
>
> At least, I appreciate the messages.


The message also serves as documentation to the reader about why this
particular point is unreachable, so I'd like to keep them.
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