[SCEV][NFC] Introduce isKnownPredicateAt method

[mkazantsev]

Summary

This method allows us to get more context for checks. Just keeping it here
until underlying patch is merged.

llvm/include/llvm/Analysis/ScalarEvolution.h

public:
   bool isKnownViaInduction(ICmpInst::Predicate Pred, const SCEV *LHS,
                            const SCEV *RHS);
 
   /// Test if the given expression is known to satisfy the condition described
   /// by Pred, LHS, and RHS.
   bool isKnownPredicate(ICmpInst::Predicate Pred, const SCEV *LHS,
                         const SCEV *RHS);
 
+  /// Test if the given expression is known to satisfy the condition described
+  /// by Pred, LHS, and RHS in the basic block BB.
+  bool isKnownPredicateAt(ICmpInst::Predicate Pred, const SCEV *LHS,
+                        const SCEV *RHS, const BasicBlock *BB);
+
   /// Test if the condition described by Pred, LHS, RHS is known to be true on
   /// every iteration of the loop of the recurrency LHS.
   bool isKnownOnEveryIteration(ICmpInst::Predicate Pred,
                                const SCEVAddRecExpr *LHS, const SCEV *RHS);
 
   /// Return true if, for all loop invariant X, the predicate "LHS `Pred` X"
   /// is monotonically increasing or decreasing.  In the former case set
   /// `Increasing` to true and in the latter case set `Increasing` to false.

llvm/lib/Analysis/ScalarEvolution.cpp

bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
 
   if (isKnownPredicateViaSplitting(Pred, LHS, RHS))
     return true;
 
   // Otherwise see what can be done with some simple reasoning.
   return isKnownViaNonRecursiveReasoning(Pred, LHS, RHS);
 }
 
+bool ScalarEvolution::isKnownPredicateAt(ICmpInst::Predicate Pred,
+                                         const SCEV *LHS, const SCEV *RHS,
+                                         const BasicBlock *BB) {
+  return isKnownPredicate(Pred, LHS, RHS) ||
+         isBasicBlockEntryGuardedByCond(BB, Pred, LHS, RHS);
+}
+
 bool ScalarEvolution::isKnownOnEveryIteration(ICmpInst::Predicate Pred,
                                               const SCEVAddRecExpr *LHS,
                                               const SCEV *RHS) {
   const Loop *L = LHS->getLoop();
   return isLoopEntryGuardedByCond(L, Pred, LHS->getStart(), RHS) &&
          isLoopBackedgeGuardedByCond(L, Pred, LHS->getPostIncExpr(*this), RHS);
 }