[Analysis] Fix a warning

This patch fixes:

  llvm/lib/Analysis/ValueTracking.cpp:116:27: error: unused function
  'safeCxtI' [-Werror,-Wunused-function]

Author: kazutakahirata

llvm/lib/Analysis/ValueTracking.cpp

@@ -113,24 +113,6 @@ static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
   return nullptr;
 }
 
-static const Instruction *safeCxtI(const Value *V1, const Value *V2, const Instruction *CxtI) {
-  // If we've been provided with a context instruction, then use that (provided
-  // it has been inserted).
-  if (CxtI && CxtI->getParent())
-    return CxtI;
-
-  // If the value is really an already-inserted instruction, then use that.
-  CxtI = dyn_cast<Instruction>(V1);
-  if (CxtI && CxtI->getParent())
-    return CxtI;
-
-  CxtI = dyn_cast<Instruction>(V2);
-  if (CxtI && CxtI->getParent())
-    return CxtI;
-
-  return nullptr;
-}
-
 static bool getShuffleDemandedElts(const ShuffleVectorInst *Shuf,
                                    const APInt &DemandedElts,
                                    APInt &DemandedLHS, APInt &DemandedRHS) {