To communicate Arm9 with FPGA you need to add businterface to that (AHB or Avalon or any other bus interface), in that bus ARM9 will be mastar and to run C code (to make communication possible between pc and ARM9 through any IDE) you need to connect RAM (external (synchronous or asynchronous)/ internal RAM ) to its reset vector locaton for that you need memory controller connected with ARM9 to its reset address and with RAM.
With this setup you will able to communicate ARM9 or any processor with FPGA.
I have did communication of CortexM1 processor with FPGA, in which I use this setup.
HTH
--
Shitansh Vaghela