[llvm-commits] [PATCH] Add RegionPass framework

[Devang Patel]

On Oct 13, 2010, at 4:21 AM, Tobias Grosser wrote:

> Hi,
> 
> ether and I would like to add a RegionPass framework to LLVM. RegionPasses are like loop passes, except that they are working on Regions provided by the RegionInfo pass instead of Loops provided by the LoopInfo pass.
> 
> The RegionPass framework was tested intensively in the Polly[1] project, where it is used since about March.
> 
> The patch contains all documentation as well as a very simple pass framework which works like the LoopPasses. We do not propose the functions needed to add/remove regions on the fly to keep the framework
> as simple as possible.
> 
> Thanks for your review
> Tobi
> 
> [1] http://wiki.llvm.org/Polyhedral_optimization_framework
> <0001-Add-RegionPass-framework.patch>_______________________________________________
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> diff --git a/include/llvm/Pass.h b/include/llvm/Pass.h
> index f4c6eed..ed0fb39 100644
> --- a/include/llvm/Pass.h
> +++ b/include/llvm/Pass.h
> @@ -57,6 +57,7 @@ enum PassManagerType {
>    PMT_CallGraphPassManager,  ///< CGPassManager
>    PMT_FunctionPassManager,   ///< FPPassManager
>    PMT_LoopPassManager,       ///< LPPassManager
> +  PMT_RegionPassManager,     ///< RGPassManager
>    PMT_BasicBlockPassManager, ///< BBPassManager
>    PMT_Last
>  };


> +// Check if this pass is suitable for the current RGPassManager, if
> +// available. This pass P is not suitable for a RGPassManager if P
> +// is not preserving higher level analysis info used by other
> +// RGPassManager passes. In such case, pop RGPassManager from the
> +// stack. This will force assignPassManager() to create new
> +// LPPassManger as expected.
> +void RegionPass::preparePassManager(PMStack &PMS) {
> +
> +  // Find RGPassManager
> +  while (!PMS.empty() &&
> +         PMS.top()->getPassManagerType() > PMT_RegionPassManager)
> +    PMS.pop();
> +


This means, if you have two region passes RGP1 & RGP2 and one loop pass LP1 in RGP1, LP1, RGP2 then LP1 will terminate RGPAssManager instance created for RGP1. In other words, you'll get following execution sequence

run RGP1 on region1
run RGP1 on region2
run LP1 on Loop 1 in region 1
run LP1 on Loop 2 in region 1
run LP1 on Loop 3 in region 2
run RGP2 on region 1
run RGP2 on region 2

If this is what you expect then this is fine. However this won't work, if you expect following pass execution sequence.

run RGP1 on region1
run LP1 on Loop 1 in region 1
run LP1 on Loop 2 in region 1
run RGP2 on region 1
run RGP1 on region2
run LP1 on Loop 3 in region 2
run RGP2 on region 2

Just a thought, may this doesn't matter. 
-
Devang