anchor.diff:        if (!instruction.isInBasicBlock()) return true;
         return everyInstruction(instruction.usedBy, (use, count) {
           return use.isInBasicBlock() &&
  -            countInstruction(use.inputs, instruction) == count;
  +            checkInstructionCount(use.inputs, instruction, count);
         });
       }
   
  
positive.code:       return everyInstruction(instruction.inputs, (input, count) {
          if (inBasicBlock) {
            return input.isInBasicBlock() &&
                countInstruction(input.usedBy, instruction) == count;
          } else {
            return countInstruction(input.usedBy, instruction) == 0;
          }
        });
      }
  
negative.code:     super.visitBasicBlock(block);
    }
  
    /// Verifies [instruction] is contained in [instructions] [count] times.
    static bool checkInstructionCount(
        List<HInstruction> instructions, HInstruction instruction, int count) {
      int result = 0;
      for (int i = 0; i < instructions.length; i++) {
        if (identical(instructions[i], instruction)) result++;
      }
      return result == count;
    }
  
    /// Returns true if the predicate returns true for every instruction in the
  