[llvm] r324450 - [LoopPrediction] Introduce utility function getLatchPredicateForGuard. NFC.

[Philip Reames via llvm-commits]

Serguei,

"Latch predicate" doesn't mean much out of context here.  Can you either 
find a more clear name or add a comment explaining the semantics of the 
new function?

Philip


On 02/06/2018 10:53 PM, Serguei Katkov via llvm-commits wrote:
> Author: skatkov
> Date: Tue Feb  6 22:53:37 2018
> New Revision: 324450
>
> URL: http://llvm.org/viewvc/llvm-project?rev=324450&view=rev
> Log:
> [LoopPrediction] Introduce utility function getLatchPredicateForGuard. NFC.
>
> Factor out getting the predicate for latch condition in a guard to
> utility function getLatchPredicateForGuard.
>
> Modified:
>      llvm/trunk/lib/Transforms/Scalar/LoopPredication.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/LoopPredication.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopPredication.cpp?rev=324450&r1=324449&r2=324450&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/LoopPredication.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopPredication.cpp Tue Feb  6 22:53:37 2018
> @@ -266,6 +266,11 @@ class LoopPredication {
>     // Return the loopLatchCheck corresponding to the RangeCheckType if safe to do
>     // so.
>     Optional<LoopICmp> generateLoopLatchCheck(Type *RangeCheckType);
> +
> +  // Returns the latch predicate for guard. SGT -> SGE, UGT -> UGE, SGE -> SGT,
> +  // UGE -> UGT, etc.
> +  ICmpInst::Predicate getLatchPredicateForGuard(ICmpInst::Predicate Pred);
> +
>   public:
>     LoopPredication(ScalarEvolution *SE) : SE(SE){};
>     bool runOnLoop(Loop *L);
> @@ -391,6 +396,30 @@ bool LoopPredication::CanExpand(const SC
>     return SE->isLoopInvariant(S, L) && isSafeToExpand(S, *SE);
>   }
>   
> +ICmpInst::Predicate
> +LoopPredication::getLatchPredicateForGuard(ICmpInst::Predicate Pred) {
> +  switch (LatchCheck.Pred) {
> +  case ICmpInst::ICMP_ULT:
> +    return ICmpInst::ICMP_ULE;
> +  case ICmpInst::ICMP_ULE:
> +    return ICmpInst::ICMP_ULT;
> +  case ICmpInst::ICMP_SLT:
> +    return ICmpInst::ICMP_SLE;
> +  case ICmpInst::ICMP_SLE:
> +    return ICmpInst::ICMP_SLT;
> +  case ICmpInst::ICMP_UGT:
> +    return ICmpInst::ICMP_UGE;
> +  case ICmpInst::ICMP_UGE:
> +    return ICmpInst::ICMP_UGT;
> +  case ICmpInst::ICMP_SGT:
> +    return ICmpInst::ICMP_SGE;
> +  case ICmpInst::ICMP_SGE:
> +    return ICmpInst::ICMP_SGT;
> +  default:
> +    llvm_unreachable("Unsupported loop latch!");
> +  }
> +}
> +
>   Optional<Value *> LoopPredication::widenICmpRangeCheckIncrementingLoop(
>       LoopPredication::LoopICmp LatchCheck, LoopPredication::LoopICmp RangeCheck,
>       SCEVExpander &Expander, IRBuilder<> &Builder) {
> @@ -415,23 +444,7 @@ Optional<Value *> LoopPredication::widen
>       DEBUG(dbgs() << "Can't expand limit check!\n");
>       return None;
>     }
> -  ICmpInst::Predicate LimitCheckPred;
> -  switch (LatchCheck.Pred) {
> -  case ICmpInst::ICMP_ULT:
> -    LimitCheckPred = ICmpInst::ICMP_ULE;
> -    break;
> -  case ICmpInst::ICMP_ULE:
> -    LimitCheckPred = ICmpInst::ICMP_ULT;
> -    break;
> -  case ICmpInst::ICMP_SLT:
> -    LimitCheckPred = ICmpInst::ICMP_SLE;
> -    break;
> -  case ICmpInst::ICMP_SLE:
> -    LimitCheckPred = ICmpInst::ICMP_SLT;
> -    break;
> -  default:
> -    llvm_unreachable("Unsupported loop latch!");
> -  }
> +  auto LimitCheckPred = getLatchPredicateForGuard(LatchCheck.Pred);
>   
>     DEBUG(dbgs() << "LHS: " << *LatchLimit << "\n");
>     DEBUG(dbgs() << "RHS: " << *RHS << "\n");
>
>
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