NAME¶
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. 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.
- -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.
EXIT STATUS¶
If
opt succeeds, it will exit with 0. Otherwise, if an error occurs, it
will exit with a non-zero value.
AUTHOR¶
Maintained by The LLVM Team (
http://llvm.org/).
COPYRIGHT¶
2003-2014, LLVM Project