anchor.diff:                              
                   static member Func = pass4
   
  +            // eliminate_tail_call_xxx are to elimate tail calls which are a problem with value types > 64 bits
  +            // and the 64-bit JIT due to the amd64 calling convention which needs to do some magic.
  +            let inline eliminate_tail_call_bool x = not (not (x))
  +            let inline eliminate_tail_call_int x = 0 + x
  +
               /// Implements generic equality between two values, with PER semantics for NaN (so equality on two NaN values returns false)
               //
               // The compiler optimizer is aware of this function  (see use of generic_equality_per_inner_vref in opt.fs)
               // and devirtualizes calls to it based on "T".
               let GenericEqualityIntrinsic (x : 'T) (y : 'T) : bool = 
  -                // The "not (not (x))" is to elimate tail calls which are a problem with value types > 64 bits
  -                not (not (GenericSpecializeEqualsWithRelation<PartialEquivalenceRelation,_>.Func.Invoke (fsEqualityComparerNoHashingPER, x, y)))
  +                eliminate_tail_call_bool (GenericSpecializeEqualsWithRelation<PartialEquivalenceRelation,_>.Func.Invoke (fsEqualityComparerNoHashingPER, x, y))
   
                   
               /// Implements generic equality between two values, with ER semantics for NaN (so equality on two NaN values returns true)
  
positive.code:             // up with differing functionality of generic and non-generic types when the IStructuralEquatable
              // this is doucmented here- https://github.com/Microsoft/visualfsharp/pull/513#issuecomment-117995410
              let GenericEqualityWithComparerIntrinsic (comp : System.Collections.IEqualityComparer) (x : 'T) (y : 'T) : bool =
                  // The "not (not (x))" is to elimate tail calls which are a problem with value types > 64 bits
                  match comp with
                  | c when obj.ReferenceEquals (c, fsEqualityComparerNoHashingER)  -> not (not (GenericEqualityERIntrinsic x y))
                  | c when obj.ReferenceEquals (c, fsEqualityComparerNoHashingPER) -> not (not (GenericEqualityIntrinsic   x y))
                  | c when obj.ReferenceEquals (c, EqualityComparer<'T>.Default)   -> not (not (EqualityComparer<'T>.Default.Equals (x, y)))
                  | _ -> comp.Equals (box x, box y)
  
              /// Implements generic equality between two values, with ER semantics for NaN (so equality on two NaN values returns true)
  
negative.code:             // and devirtualizes calls to it based on type "T".
              let GenericHashIntrinsic x = 
                  let iec = fsEqualityComparerUnlimitedHashingPER
                  eliminate_tail_call_int (GenericSpecializeHash.Func.Invoke (iec, x))
  
              /// Intrinsic for calls to depth-limited structural hashing that were not optimized by static conditionals.
              let LimitedGenericHashIntrinsic limit x =
                  let iec = CountLimitedHasherPER limit
                  eliminate_tail_call_int (GenericSpecializeHash.Func.Invoke (iec, x))
  
              /// Intrinsic for a recursive call to structural hashing that was not optimized by static conditionals.
              //
  