[LLVMdev] Add a 'notrap' function attribute?

[Philip Reames]

On 11/1/13 2:07 PM, Andrew Trick wrote:
>
> - I'm not sure why divide-by-zero would motivate this (probably just 
> missing something). LLVM doesn't model it as a trap currently. And if 
> it did, an explicit nonzero-divisor check would be easy to reason 
> about without any metadata.
This is far enough off topic to not be worth discussing now, but I want 
to throw out that there would be interested parties in defining trapping 
versions of LLVM instructions which currently use undef semantics for 
edge cases.  We haven't dug into this much yet, but it is something 
we're probably going to be interested in long term. Our initial approach 
is to simply use explicit conditional guards to handle things like 
div-by-zero and null-dereference.  Depending on the performance we see 
with that approach, we may be interested in implementing support for 
implicit checks which would likely require explicitly trapping semantics.

Philip

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