CODEWITHSUNDEEP
llvm
Sherwood Wang
Sherwood Wang

Reputation: 715

Passing command line arguments when profiling with llvm-prof

How can I pass command line arguments to my program when profiling with llvm-prof?

And where can I find a more comprehensive documentation for llvm-prof? "llvm-prof -help" output is too brief. Its manual is even shorter.

Upvotes: 0

Views: 459

Answers (2)

shrm
shrm

Reputation: 1140

The way you write the question implies that you are trying to execute your program using llvm-prof. However I am not sure if that is the way to do it. The way to profile is first to instrument your code with counters using:

opt -disable-opt -insert-edge-profiling -o program.profile.bc program.bc

Then execute the instrumented program using lli as follows:

lli -O0 -fake-argv0 'program.bc < YOUR_ARGS' -load llvm/Debug+Asserts/lib/libprofile_rt.so program.profile.bc

Note the way to pass the arguments to the program using -fake-argv0 'program.bc < YOUR_ARGS' above. This step will generate llvmprof.out file which can then be read with llvm-prof to generate the execution profiles as follows:

llvm-prof program.profile.bc

Upvotes: 1

Eli Bendersky
Eli Bendersky

Reputation: 273416

I would recommend staying away from llvm-prof at this point. The reason is that it was actually removed from trunk LLVM a month ago (in revision 191835). Here is the commit message that should clarify the motivation:

Remove the very substantial, largely unmaintained legacy PGO
infrastructure.

This was essentially work toward PGO based on a design that had several
flaws, partially dating from a time when LLVM had a different
architecture, and with an effort to modernize it abandoned without being
completed. Since then, it has bitrotted for several years further. The
result is nearly unusable, and isn't helping any of the modern PGO
efforts. Instead, it is getting in the way, adding confusion about PGO
in LLVM and distracting everyone with maintenance on essentially dead
code. Removing it paves the way for modern efforts around PGO.

Among other effects, this removes the last of the runtime libraries from
LLVM. Those are being developed in the separate 'compiler-rt' project
now, with somewhat different licensing specifically more approriate for
runtimes.

Upvotes: 4

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