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.


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.

Print a summary of command line options.

-o filename
Specify the output filename.

-profile-info-file filename
Specify the name of the file loaded by the -profile-loader option.

Print statistics.

Record the amount of time needed for each pass and print it to standard error.

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 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 -help

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 (