Question

I want to see the profile of LLVM IR programs. Does simplescalar simulator support LLVM? Are there any other simulators to do the same?

Answer 1

If Simplescalar supports ARM and x86 ELF binaries, it can be used with LLVM-compiled programs.

But if you want to do simple profiling (what time takes each part of program when running on real CPU), you can check more known profilers like:

• google-perftools or
• callgrind/cachegrind or
• oprofile.

You can’t just run a LLVM IR, because IR of LLVM is not supported in SimpleScalar or in usual profilers. IR is supported by lli and other llvm tools.

If you want to profile which branches are used and how often, there is LLVM profiling for PGO (profile-guided optimizations). There are llvm-prof utility and utils/profile.pl script to profile LLVM IR programs.

Howto from utils/profile.pl source:

# Program:  profile.pl
#
# Synopsis: Insert instrumentation code into a program, run it with the JIT,
#           then print out a profile report.
#
# Syntax:   profile.pl [OPTIONS] bytecodefile <arguments>
#
# OPTIONS may include one or more of the following:
#     -block    - Enable basicblock profiling
#     -edge     - Enable edge profiling
#     -function - Enable function profiling
#     -o <filename> - Emit profiling information to the specified file, instead
#                     of llvmprof.out
#
# Any unrecognized options are passed into the invocation of llvm-prof

Internally it is

1. running of opt with some -insert-*-profiling Pass. output is instrumented IR
2. running the intrumented IR with lli (with hope of using JIT)
3. starting llvm-prof to convert llvmprof.out to readable text

PS there is some research paper about LLLVM profiling: llvm.org/pubs/2010-04-NeustifterProfiling.pdf