How to track down a bad llvm optimization pass

[Joakim via digitalmars-d-ldc]

On Saturday, 2 July 2016 at 07:42:31 UTC, Johan Engelen wrote:
> On Saturday, 2 July 2016 at 07:29:47 UTC, Joakim wrote:
>> 
>> I was surprised that llvm is just silently doing this, with no 
>> warning.
>
> This blog article gives some insight:
> http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_21.html

Thanks for the link, it's very relevant.  I've mentioned these 
issues and closed the llvm bug as invalid, as that GVN pass was 
only surfacing this undefined behavior.

Leaving aside the optimizer, the unoptimized phobos debug tests 
should have caught this, shouldn't they?  I'll look into why 
those passed next.