regarding llvm compiler and profiler

Dear All,

I’m a new bee in using LLVM environment.
I have certain doubts in using compiler and profiler. Please, someone explain how and why it is so?

compiler: What is the default optimization level in llvm-gcc?

profiler: 1. During basic block profiling why all functions are not listed.
2. In function execution frequencies, why only 6 functions are listed?
3. There is no information about main() function in profiling many of the applications. Why is it so?

With Thanks,

R.D.PATEL
Research Scholar,E.C.E. Department
MANIT, Bhopal
M:(91)8085090402, H:(91)8602677554