bf inst

Name

bf-inst - Insert Byfl instrumentation into an LLVM bitcode file

Synopsis

bf-inst [-o bitcode_file] [-Oopt_level] [--bf-verbose] [--bf-clang-args] [-bf-plugin=path/to/bytesflops.so] [--bf-static] [Byfl options] bitcode_file

bf-inst --help

Description

bf-inst uses Byfl to instrument a given LLVM bitcode file with tallies of how many times various operations were executed. It serves as a lower-level interface to Byfl instrumentation than that which is provided by bf-clang and related Byfl compiler wrapper scripts in that bf-inst expects the user already to have produced LLVM bitcode from program source code.

Options

• --help

  Display bf-inst usage information.

• -o bitcode_file

  Specify the name of the bitcode file to generate. If not specified, the input file is overwritten.

• -Oopt_level

  Designate the optimization level at which opt should optimize the bitcode after Byfl instrumentation has been applied.

• --bf-verbose

  Display all of the file operations that bf-inst performs.

• -bf-plugin=path/to/bytesflops.so

  Point bf-inst to the Byfl plugin (bytesflops.so).

• --bf-clang-args

  Instead of instrumenting any bitcode, display a command-line fragment that can be passed to clang or clang++ to instruct those programs to invoke Byfl themselves.

• -bf-static

  Output static instruction counts at compile time.

bf-inst passes any additional options, such as -bf-by-func, to LLVM's opt program. The other Byfl wrapper-script man pages (e.g., bf-clang(1)) document all of the Byfl-specific options.

The command line ends with a list of bitcode files. These may be in binary (.bc) or ASCII (.ll) format and can even be renamed (e.g., to .o in case an existing Makefile is retrofitted to emit bitcode without altering output filenames). In addition, bf-inst automatically instruments the contents of ar (.a) archives.

Examples

bf-inst is intended to be used on existing bitcode files as an explicit part of the build process:

clang -O2 -emit-llvm -c myfile.c -o myfile.bc
bf-inst -bf-verbose -bf-types -bf-by-func myfile.bc
clang -o myfile myfile.bc -lbyfl

An alternative way to use bf-inst is

clang -O2 `bf-inst -bf-clang-args -bf-types -bf-by-func` \
  -o myfile.o -c myfile.c

This has the advantage of being easier to integrate into an existing build system but the disadvantage that Byfl instrumentation is performed in the middle of LLVM's set of optimization passes instead of after all optimizations have been performed. Furthermore, it sacrifices the post-instrumentation optimization pass.

Author

Scott Pakin, [email protected]

See also

ar(1), bf-clang(1), clang(1), opt(1), the Byfl README file