[llvm-dev] Infinite loops with no side effects

[Hal Finkel via llvm-dev]

On 10/27/2017 03:12 PM, Reid Kleckner wrote:
> On Fri, Oct 27, 2017 at 1:08 PM, Hal Finkel <hfinkel at anl.gov 
> <mailto:hfinkel at anl.gov>> wrote:
>
>     On 10/27/2017 02:51 PM, Reid Kleckner wrote:
>
>>     Personally, I don't like the side effect intrinsic.
>
>     Understood. I also don't like the fact that it will clutter the IR
>     in many cases.
>
>>     It will pollute all the IR generated by non-C frontends. What
>>     most of these frontends really want is just a switch to disable a
>>     targeted set of optimizations.
>>
>>     One thing I like about the function attribute idea is that it's
>>     conservatively correct to discard it when doing cross-language
>>     inlining. It just becomes something that C-family frontends need
>>     to remember to add to enable their special-case language rules,
>>     rather than something that non-C languages need to think about.
>>     Similar to the 'access', builtin vs nonbuiltin discussion
>>     happening in parallel, the attribute enables the optimization,
>>     rather than inhibiting it.
>
>     As I said below, a function attribute is insufficient. It needs to
>     be something we can mark per loop. This is needed to correctly
>     model C. The sideeffect intrinsic is the best proposal I've seen
>     so far.
>
>
> Maybe we should do both? If the intrinsic is a special case, that 
> seems fine. It's cheap.

Okay.

  -Hal

-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171027/a8da6103/attachment.html>