How to profile a program with llvm tools with llvm 3.5 or greater?

Question

I am looking into using llvm tools to generate block level profile of small programs. It looks like in older versions this was as simple as running:

perl utils/profile.pl -block program.bc

How is profiling done in newer versions of LLVM?

Answer 1

Use Clang and llvm-profdata

Visit the Clang User's Manual profile with instrumentation

llvm doc llvm-profdata

In summary:

1. Build an instrumented version of the code

   clang -O2 -fprofile-instr-generate code.c
   

2. Run the instrumented executable to get the profile data file

   ./a.out
   

3. Combine profiles from multiple runs and format the files by running

   llvm-profdata merge *.profraw -output=code.profdata
   

4. Build the code again

   clang -O2 -fprofile-instr-use=code.profdata code.c
   

(Optional?) 5. Display the profile counters for this file and for any of the specified function(s)

    llvm-profdata show -all-functions code.profdata