The opt command is the modular LLVM optimizer and analyzer.
It takes LLVM source files as input, runs the specified optimizations or
analyses on it, and then outputs the optimized file 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 the input source. 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 output 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.
Inputs can be in either the LLVM assembly language format (.ll) or
the LLVM bitcode format (.bc).
If an output filename is not specified with the -o option,
opt writes its output to the standard output.
- -f
- Enable binary output on terminals. Normally, opt will refuse to
write raw bitcode output if the output stream is a terminal. With this
option, opt will write raw bitcode regardless of the output
device.
- -help
- Print a summary of command line options.
- -S
- Write output in LLVM intermediate language (instead of bitcode).
- -{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).
- -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.
- -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 LLVM_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
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 (https://llvm.org/).