llvm dev - Sep 2012 - [LLVMdev] Profiling - execution count of basic blocks...

Hi gang,  time for my weekly confusion... (I'm trying not to bombard the
board with questions)

The thing that's on my mind at the moment (there's some backend-stuff
that
I'm just working my way though) is that I'm not getting very far when
trying to get LLVM to profile code - I'm looking for nothing more special
than list of how many times each basic block has been called - but when
wading though the docs I get lots of command line fragments that don't work
and the distint impression that the method for profiling has changed three
times in the last three release - I don't suppose that you have any insight
into what's going on with profiling for llvm...?  I'm starting to get
the
feeling that I've missed something obvious...   My setup is:

LLVM (http://llvm.org/):
  LLVM version 3.2svn
  DEBUG build with assertions.
  Built Jul 27 2012 (18:29:09).
  Default target: x86_64-apple-darwin11.4.0
  Host CPU: corei7-avx

Any ideas?
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We recently got some profiling going with llvm 3.1. (Alastair has got some code
in for metadata generation after reading the profiled data(post 3.1) which you
can follow in some of the earlier mail chains). I will describe the (earlier)
3.1 method which has worked for us. Note this is just a way of doing it. Not
*the* way.

Assume you are using clang/clang++ and have a set of C/C++ files:


a)      Run individual C/C++ files with : clang/clang++ -mllvm  -emit-llvm -S -o
x.o x.c/x.cpp

b)      Link all the .o s using llvm-link: llvm-link *.o -o X.o // new single
X.o created

c)       Insert edge profiling: opt -O3  -insert-edge-profiling X.o -o X_prof.o

d)      llc X_prof.o // creates X_prof.o.s

e)      as X_prof.o.s // creates a.out

f)       clang/clang++ -o X_prof.exe a.out -lprofile_rt -L<path of your
installed lib where libprofile_rt resides> //creates the instrumented binary
X_prof.exe

Now run the instrumented executable "X_prof.exe" using whatever input
test data you have. This will create the llvmprof.out file.

Create the new optimized executable after reading llvmprof.out:

g)       opt -O3 -profile-loader X.o -o X_opt.o   // you can replace this with
Alastair's profile loading step -profile-metadata-loader

h)      llc X_opt.o // creates X_opt.o.s

i)        as X_opt.o.s // creates a.out

j)        clang/clang++ -o X_opt.exe a.out -lprofile_rt -L<path of your
installed lib where libprofile_rt resides> //creates the final optimized
binary X_opt.exe

Hope this helps.

-Dibyendu


From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Joseph Reddington
Sent: Monday, September 10, 2012 1:32 PM
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] Profiling - execution count of basic blocks...

Hi gang,  time for my weekly confusion... (I'm trying not to bombard the
board with questions)

The thing that's on my mind at the moment (there's some backend-stuff
that I'm just working my way though) is that I'm not getting very far
when trying to get LLVM to profile code - I'm looking for nothing more
special than list of how many times each basic block has been called - but when
wading though the docs I get lots of command line fragments that don't work
and the distint impression that the method for profiling has changed three times
in the last three release - I don't suppose that you have any insight into
what's going on with profiling for llvm...?  I'm starting to get the
feeling that I've missed something obvious...   My setup is:

LLVM (http://llvm.org/):
  LLVM version 3.2svn
  DEBUG build with assertions.
  Built Jul 27 2012 (18:29:09).
  Default target: x86_64-apple-darwin11.4.0
  Host CPU: corei7-avx

Any ideas?
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