docs/CommandGuide/opt.rst

opt - LLVM optimizer
====================


SYNOPSIS
--------


**opt** [*options*] [*filename*]


DESCRIPTION
-----------


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.


OPTIONS
-------



**-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.



**-o** *filename*

 Specify the output filename.



**-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).



**-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:


 .. code-block:: sh

     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:


 .. code-block:: sh

     opt -load=plugin.so -help




**-p**

 Print module after each transformation.




EXIT STATUS
-----------


If **opt** succeeds, it will exit with 0.  Otherwise, if an error
occurs, it will exit with a non-zero value.