For RL78 there are two diffrent Flash self Programming Library . first one is CC-RL compiler version and second one is CA78K0R compiler. Which one if suitable for IAR.
At the European download area you find library packages for IAR compiler:
Due to the ABI compatibility between Renesas CCRL compiler and IAR compiler V2.xx, you can use the CCRL libraries also for IAR compiler. But as the corresponding header files are different, I strongly recommend to use the IAR library packages.