[llvm-dev] [SPIR/PTX] Divergence analysis for BasicBlocks

Alexandre Isoard via llvm-dev
Fri, 21 Jul 2017 15:21:25 -0000

Hello,

Yes? Where is allActive defined, I couldn't find it.

Basically, a BB is control divergent if it's execution depends on a branch
that itself depends on a divergent ssa value.

On Fri, Jul 21, 2017 at 4:13 PM, Zaks, Ayal <ayal.zaks at intel.com>
wrote:

> What would be the definition of “isControlDivergent(BasicBlock*)”; the
> complementary of “allActive(BasicBlock*)” – blocks known to execute all
> lanes, whenever reached? Note the (distinct) term “rewire targets” that
> Ralf Karrenberg used in his thesis.
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
*Alexandre
> Isoard via llvm-dev
> *Sent:* Friday, July 14, 2017 20:53
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [llvm-dev] [SPIR/PTX] Divergence analysis for BasicBlocks
>
>
>
> Hello,
>
>
>
> It seems to me that our current DivergenceAnalysis does not save which
> BasicBlocks may suffer from divergent control. Am I correct?
>
>
>
> I want to modify our DivergenceAnalysis to add a "bool
> isControlDivergent(BasicBlock*) const" method and save in the
divergence
> propagator the basicblock that are divergent. I am not sure that is
> entirely correct, if you have input on that please let me know.
>
>
>
> That being said, to ease my debugging process I want to introduce a
> -dot-divergence pass that dump the cfg with divergent basicblocks in red. I
> was wondering if our dot printer is flexible enough to allow me to also
> print in color the SSA variables that are divergent.
>
>
>
> Thanks.
>
>
>
> --
>
> *Alexandre Isoard*
>
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--
*Alexandre Isoard*
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