[llvm] 0be9940 - [SCEV] Don't check if propagation safe if there are no flags (NFC)

[Philip Reames via llvm-commits]

Good idea, thanks.

Philip

On 10/5/21 1:27 PM, Nikita Popov via llvm-commits wrote:
> Author: Nikita Popov
> Date: 2021-10-05T22:25:41+02:00
> New Revision: 0be9940ef240d04111c7ef7df360c3b4209dfdea
>
> URL: https://github.com/llvm/llvm-project/commit/0be9940ef240d04111c7ef7df360c3b4209dfdea
> DIFF: https://github.com/llvm/llvm-project/commit/0be9940ef240d04111c7ef7df360c3b4209dfdea.diff
>
> LOG: [SCEV] Don't check if propagation safe if there are no flags (NFC)
>
> If there are no nowrap flags, then we don't need to determine
> whether propagating flags is safe -- it will make no difference.
>
> Added:
>      
>
> Modified:
>      llvm/lib/Analysis/ScalarEvolution.cpp
>
> Removed:
>      
>
>
> ################################################################################
> diff  --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
> index c09180b2c197..6683b1a5205c 100644
> --- a/llvm/lib/Analysis/ScalarEvolution.cpp
> +++ b/llvm/lib/Analysis/ScalarEvolution.cpp
> @@ -2802,11 +2802,13 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
>         // Proving that entry to the outer scope neccesitates entry to the inner
>         // scope, thus proves the program undefined if the flags would be violated
>         // in the outer scope.
> -      auto *DefI = getDefiningScopeBound(LIOps);
> -      auto *ReachI = &*AddRecLoop->getHeader()->begin();
> -      const bool CanPropagateFlags =
> -        isGuaranteedToTransferExecutionTo(DefI, ReachI);
> -      auto AddFlags = CanPropagateFlags ? Flags : SCEV::FlagAnyWrap;
> +      SCEV::NoWrapFlags AddFlags = Flags;
> +      if (AddFlags != SCEV::FlagAnyWrap) {
> +        auto *DefI = getDefiningScopeBound(LIOps);
> +        auto *ReachI = &*AddRecLoop->getHeader()->begin();
> +        if (!isGuaranteedToTransferExecutionTo(DefI, ReachI))
> +          AddFlags = SCEV::FlagAnyWrap;
> +      }
>         AddRecOps[0] = getAddExpr(LIOps, AddFlags, Depth + 1);
>   
>         // Build the new addrec. Propagate the NUW and NSW flags if both the
>
>
>          
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