[Beignet] [PATCH] Refine custom unrolling policy.

[Yang, Rong R]

LGTM, pushed, thanks.

> -----Original Message-----
> From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of
> Zhigang Gong
> Sent: Friday, March 4, 2016 14:53
> To: beignet at lists.freedesktop.org
> Cc: Zhigang Gong <zhigang.gong at linux.intel.com>
> Subject: [Beignet] [PATCH] Refine custom unrolling policy.
> 
> We should use the production of current trip count and parent trip count to
> determine whether we should unroll the parent loop.
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at linux.intel.com>
> ---
>  backend/src/llvm/llvm_unroll.cpp | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/backend/src/llvm/llvm_unroll.cpp
> b/backend/src/llvm/llvm_unroll.cpp
> index 0f62bdc..a289c11 100644
> --- a/backend/src/llvm/llvm_unroll.cpp
> +++ b/backend/src/llvm/llvm_unroll.cpp
> @@ -176,6 +176,12 @@ namespace gbe {
>          if (ExitBlock)
>            currTripCount = SE->getSmallConstantTripCount(L, ExitBlock);
> 
> +        if (currTripCount > 32) {
> +          shouldUnroll = false;
> +          setUnrollID(currL, false);
> +          return shouldUnroll;
> +        }
> +
>          while(currL) {
>            Loop *parentL = currL->getParentLoop();
>            unsigned parentTripCount = 0; @@ -187,20 +193,17 @@ namespace
> gbe {
>              if (parentExitBlock)
>                parentTripCount = SE->getSmallConstantTripCount(parentL,
> parentExitBlock);
>            }
> -          if ((parentTripCount != 0 && currTripCount / parentTripCount > 16) ||
> -              (currTripCount > 32)) {
> -            if (currL == L)
> -              shouldUnroll = false;
> -            setUnrollID(currL, false);
> -            if (currL != L)
> +          if (parentTripCount != 0 && currTripCount * parentTripCount > 32) {
> +            setUnrollID(parentL, false);
>  #if LLVM_VERSION_MAJOR == 3 &&  LLVM_VERSION_MINOR >= 8
> -              loopInfo.markAsRemoved(currL);
> +            loopInfo.markAsRemoved(parentL);
>  #else
> -              LPM.deleteLoopFromQueue(currL);
> +            LPM.deleteLoopFromQueue(parentL);
>  #endif
> +            return shouldUnroll;
>            }
>            currL = parentL;
> -          currTripCount = parentTripCount;
> +          currTripCount = parentTripCount * currTripCount;
>          }
>          return shouldUnroll;
>        }
> --
> 2.1.4
> 
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