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
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
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.