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
