Questions about Avalon Performance Counter

1. alt_get_cpu_freq() is not defined by "altera_avalon_performance_counter.h",

which header file can I use for this function?

2. When I run the program using Nios II instruction set simulator, it gave me a

warning : "SOPC Builder system component performance_counter_0 is not

supported by the simulator. Simulation may be incorrect if your software

attempts to access it". Also I got an error: "Error! Failed memory access in

component cpu_0 - Reading data 0x0 from uninitialized memory (addr =

0x3ff68) Error! : Simulation failed in component cpu_0 at instruction 3257

(PC=0x21e4 instr=0x24000317)." So, which tool except Modelsim can I use to

run the program with performance counter? Actually, Modelsim is very slow if

running a very large code.

Thank you very much!