[llvm-dev] [RFC] IR-level Region Annotations
Hal Finkel via llvm-dev
llvm-dev at lists.llvm.org
Tue Jan 17 19:01:52 PST 2017
On 01/17/2017 06:59 PM, Mehdi Amini wrote:
>> On Jan 17, 2017, at 4:36 PM, Hal Finkel via llvm-dev
>> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> On 01/17/2017 05:36 PM, Wael Yehia via llvm-dev wrote:
>>> Hi. Regarding the token approach, I've read some documentation
>>> (review D11861, EH in llvm, and Reid and David's presentation) but
>>> couldn't answer the following question.
>>> Does the intrinsic or the instruction returning a /token/ type
>>> object act as a code motion barrier? In other words, does it prevent
>>> other operations from being reordered with it?
>>> If the answer is no, then does it mean the intrinsic has to be
>>> marked with the /convergent/ property to achieve the code motion
>>> barrier effect?
>> To clarify, convergent does not form a code-motion barrier. It
>> prevents transformations from adding additional control dependencies.
>> I suspect that the token type does the same (because tokens can't
>> appear in PHIs).
> What if the only user of the token is in a branch? It seems to me that
> you’d be allowed to sink the token producer there, but not if it is
> marked convergent.
Can that happen if you start out with a "well formed" region?
>> Actual code motion barriers are generally achieved by adding unknown
>> memory dependencies.
>>> If yes, can someone explain how is that achieved in llvm?
>>> Greatly appreciated. Thanks.
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>> Hal Finkel
>> Lead, Compiler Technology and Programming Languages
>> Leadership Computing Facility
>> Argonne National Laboratory
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the llvm-dev