mehdi_amini added a comment.

In D69498#1727080 <https://reviews.llvm.org/D69498#1727080>, @jdoerfert wrote:

> Let me quote @arsenm here because this is so important: "Basically no 
> frontend has gotten this right, including clang and non-clang frontends." For 
> me, that statement alone is reason to change the status quo.


I am not convinced by this: this seems overly simplistic. The fact that 
convergent wasn't rolled out properly in frontend can also been as an artifact 
of the past. There is a logical gap between this and concluding that the only 
solution is to change the default. For instance someone mentioned a pass that 
could be inserted as the very beginning of the pipeline by any GPU compiler and 
add the convergent attribute everywhere.

>> As of the frontend, it seems to me that this is just about structuring the 
>> code-path for function emission to define the right set of default 
>> attribute. It isn't clear to me why a refactoring of the frontend isn't a 
>> better course of actions here.
> 
> Whatever we do, there will be consequences for current and future front-ends. 
> At the end of the day, the underlying question we need to answer here is: Do 
> we want to have "optimization with opt-in soundness" or "soundness with 
> opt-in optimizations", and I would choose the latter any time.

This view seems appropriate to me only if you consider a GPU (or SIMT) compiler 
alone. Another view (which seems to be what @rjmccall has) is that SIMT/GPU is 
a marginal use-case and "soundness" is already existing for most LLVM use-cases.


CHANGES SINCE LAST ACTION
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https://reviews.llvm.org/D69498



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