opt - LLVM optimizer
opt [options] [filename]
The opt command is the modular LLVM optimizer and analyzer. It takes LLVM
bytecode as input, runs the specified optimizations or analyses on it, and then
outputs the optimized LLVM bytecode or the analysis results. The function of
opt depends on whether the -analyze option is given.
When -analyze is specified, opt performs various analyses of LLVM
bytecode. It will usually print the results on standard output, but in a few
cases, it will print output to standard error or generate a file with the
analysis output, which is usually done when the output is meant for another
program.
While -analyze is not given, opt attempts to produce an optimized
bytecode file. The optimizations available via opt depend upon what
libraries were linked into it as well as any additional libraries that have
been loaded with the -load option. Use the -help option to determine
what optimizations you can use.
If filename is omitted from the command line or is -, opt reads its
input from standard input. The input must be an LLVM bytecode file.
If an output filename is not specified with the -o option, opt
writes its output to the standard output.
- -f
-
Force overwrite. Normally, opt will refuse to overwrite an
output file that already exists. With this option, opt will
overwrite the output file and replace it with new bytecode.
- -help
-
Print a summary of command line options.
- -o filename
-
Specify the output filename.
- -{passname}
-
opt provides the ability to run any of LLVM's optimization or analysis passes
in any order. The -help option lists all the passes available. The order in
which the options occur on the command line are the order in which they are
executed (within pass constraints).
- -std-compile-opts
-
This is short hand for a standard list of compile time optimization passes.
This is typically used to optimize the output from the llvm-gcc front end. It
might be useful for other front end compilers as well. To discover the full set
of options available, use the following command:
-
llvm-as < /dev/null | opt -std-compile-opts -disable-output -debug-pass=Arguments
- -disable-inlining
-
This option is only meaningful when -std-compile-opts is given. It simply
removes the inlining pass from the standard list.
- -disable-opt
-
This option is only meaningful when -std-compile-opts is given. It disables
most, but not all, of the -std-compile-opts. The ones that remain are
-verify, -lower-setjmp, and -funcresolve.
- -strip-debug
-
This option causes opt to strip debug information from the module before
applying other optimizations. It is essentially the same as -strip but it
ensures that stripping of debug information is done first.
- -verify-each
-
This option causes opt to add a verify pass after every pass otherwise specified
on the command line (including -verify). This is useful for cases where it
is suspected that a pass is creating an invalid module but it is not clear which
pass is doing it. The combination of -std-compile-opts and -verify-each
can quickly track down this kind of problem.
- -profile-info-file filename
-
Specify the name of the file loaded by the -profile-loader option.
- -stats
-
Print statistics.
- -time-passes
-
Record the amount of time needed for each pass and print it to standard
error.
- -debug
-
If this is a debug build, this option will enable debug printouts
from passes which use the DEBUG() macro. See the LLVM Programmer's
Manual, section #DEBUG for more information.
- -load=plugin
-
Load the dynamic object plugin. This object should register new optimization
or analysis passes. Once loaded, the object will add new command line options to
enable various optimizations or analyses. To see the new complete list of
optimizations, use the -help and -load options together. For example:
-
opt -load=plugin.so -help
- -p
-
Print module after each transformation.
If opt succeeds, it will exit with 0. Otherwise, if an error
occurs, it will exit with a non-zero value.
Maintained by the LLVM Team (http://llvm.org).