[Beignet] [PATCH v2] add the reduced self loop node detection.

[Zhigang Gong]

This version LGTM, pushed, thanks.

On Wed, Nov 19, 2014 at 01:38:30PM +0800, xionghu.luo at intel.com wrote:
> From: Luo Xionghu <xionghu.luo at intel.com>
> 
> if the self loop node is reduced, the llvm loop info couldn't detect
> such kind of self loops, handle it by checking whether the compacted
> node has a successor pointed to itself.
> 
> v2: differentiate the compacted node from basic node to make the logic
> clearer, comments the while node as it is not enabled now.
> 
> Signed-off-by: Luo Xionghu <xionghu.luo at intel.com>
> ---
>  backend/src/ir/structural_analysis.cpp |   37 ++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/backend/src/ir/structural_analysis.cpp b/backend/src/ir/structural_analysis.cpp
> index 21c04f3..4c7e3d2 100644
> --- a/backend/src/ir/structural_analysis.cpp
> +++ b/backend/src/ir/structural_analysis.cpp
> @@ -864,6 +864,9 @@ namespace analysis
>          return NULL;
>      }
>  
> +    //FIXME: as our IR could only handle self loop, the while loop node
> +    //is disabled to avoid performace regression by the path function.
> +#if 0
>      /* check for improper region */
>      for(NodeList::const_iterator m = nset.begin(); m != nset.end(); m++)
>      {
> @@ -888,6 +891,8 @@ namespace analysis
>          return insertNode(p);
>        }
>      }
> +#endif
> +
>      return NULL;
>    }
>  
> @@ -1023,18 +1028,28 @@ namespace analysis
>            }
>  
>            Node* loop_header = NULL;
> -          for (auto l : loops) {
> -            ir::BasicBlock &a = fn->getBlock(l->bbs[0]);
> -            loop_header = bbmap.find(&a)->second;
> -
> -            if(loop_header == n){
> -              for (auto bb : l->bbs) {
> -                ir::BasicBlock &tmp = fn->getBlock(bb);
> -                Node* node_ = bbmap.find(&tmp)->second;
> -                reachUnder.push_front(node_);
> -                nset.insert(node_);
> +          //if n is basic block node, query the llvm loop info to find the loop whoose loop header is n;
> +          if(n->type() == BasicBlock){
> +            for (auto l : loops) {
> +              ir::BasicBlock &a = fn->getBlock(l->bbs[0]);
> +              loop_header = bbmap.find(&a)->second;
> +
> +              if(loop_header == n){
> +                for (auto bb : l->bbs) {
> +                  ir::BasicBlock &tmp = fn->getBlock(bb);
> +                  Node* node_ = bbmap.find(&tmp)->second;
> +                  reachUnder.push_front(node_);
> +                  nset.insert(node_);
> +                }
> +                break;
>                }
> -              break;
> +            }
> +          }else{
> +          //n is compacted node, it would have a successor pointed to itself for self loop.
> +            if(n->succs().find(n) != n->succs().end())
> +            {
> +                reachUnder.push_front(n);
> +                nset.insert(n);
>              }
>            }
>  
> -- 
> 1.7.9.5
> 
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