[llvm] r278854 - [LoopUnroll] Don't clear out the AssumptionCache on each loop

[Hal Finkel via llvm-commits]

Thanks!

FYI, we essentially have the same FIXME in Scalar/LoopUnswitch.cpp and Utils/InlineFunction.cpp, in case you'd like to take a look.

 -Hal

----- Original Message -----
> From: "David Majnemer via llvm-commits" <llvm-commits at lists.llvm.org>
> To: llvm-commits at lists.llvm.org
> Sent: Tuesday, August 16, 2016 4:09:46 PM
> Subject: [llvm] r278854 - [LoopUnroll] Don't clear out the AssumptionCache on each loop
> 
> Author: majnemer
> Date: Tue Aug 16 16:09:46 2016
> New Revision: 278854
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=278854&view=rev
> Log:
> [LoopUnroll] Don't clear out the AssumptionCache on each loop
> 
> Clearing out the AssumptionCache can cause us to rescan the entire
> function for assumes.  If there are many loops, then we are scanning
> over the entire function many times.
> 
> Instead of clearing out the AssumptionCache, register all cloned
> assumes.
> 
> Modified:
>     llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
> 
> Modified: llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp?rev=278854&r1=278853&r2=278854&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp Tue Aug 16
> 16:09:46 2016
> @@ -28,6 +28,7 @@
>  #include "llvm/IR/BasicBlock.h"
>  #include "llvm/IR/DataLayout.h"
>  #include "llvm/IR/Dominators.h"
> +#include "llvm/IR/IntrinsicInst.h"
>  #include "llvm/IR/LLVMContext.h"
>  #include "llvm/Support/Debug.h"
>  #include "llvm/Support/raw_ostream.h"
> @@ -486,9 +487,14 @@ bool llvm::UnrollLoop(Loop *L, unsigned
>      }
>  
>      // Remap all instructions in the most recent iteration
> -    for (BasicBlock *NewBlock : NewBlocks)
> -      for (Instruction &I : *NewBlock)
> +    for (BasicBlock *NewBlock : NewBlocks) {
> +      for (Instruction &I : *NewBlock) {
>          ::remapInstruction(&I, LastValueMap);
> +        if (auto *II = dyn_cast<IntrinsicInst>(&I))
> +          if (II->getIntrinsicID() == Intrinsic::assume)
> +            AC->registerAssumption(II);
> +      }
> +    }
>    }
>  
>    // Loop over the PHI nodes in the original block, setting incoming
>    values.
> @@ -601,10 +607,6 @@ bool llvm::UnrollLoop(Loop *L, unsigned
>      }
>    }
>  
> -  // FIXME: We could register any cloned assumptions instead of
> clearing the
> -  // whole function's cache.
> -  AC->clear();
> -
>    // FIXME: We only preserve DT info for complete unrolling now.
>    Incrementally
>    // updating domtree after partial loop unrolling should also be
>    easy.
>    if (DT && !CompletelyUnroll)
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory