| John Bauman | 66b8ab2 | 2014-05-06 15:57:45 -0400 | [diff] [blame^] | 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | opt - LLVM optimizer
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | B<opt> [I<options>] [I<filename>]
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| 10 |
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| 11 | =head1 DESCRIPTION
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| 12 |
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| 13 | The B<opt> command is the modular LLVM optimizer and analyzer. It takes LLVM
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| 14 | source files as input, runs the specified optimizations or analyses on it, and then
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| 15 | outputs the optimized file or the analysis results. The function of
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| 16 | B<opt> depends on whether the B<-analyze> option is given.
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| 17 |
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| 18 | When B<-analyze> is specified, B<opt> performs various analyses of the input
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| 19 | source. It will usually print the results on standard output, but in a few
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| 20 | cases, it will print output to standard error or generate a file with the
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| 21 | analysis output, which is usually done when the output is meant for another
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| 22 | program.
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| 23 |
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| 24 | While B<-analyze> is I<not> given, B<opt> attempts to produce an optimized
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| 25 | output file. The optimizations available via B<opt> depend upon what
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| 26 | libraries were linked into it as well as any additional libraries that have
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| 27 | been loaded with the B<-load> option. Use the B<-help> option to determine
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| 28 | what optimizations you can use.
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| 29 |
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| 30 | If I<filename> is omitted from the command line or is I<->, B<opt> reads its
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| 31 | input from standard input. Inputs can be in either the LLVM assembly language
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| 32 | format (.ll) or the LLVM bitcode format (.bc).
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| 33 |
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| 34 | If an output filename is not specified with the B<-o> option, B<opt>
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| 35 | writes its output to the standard output.
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| 36 |
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| 37 | =head1 OPTIONS
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| 38 |
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| 39 | =over
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| 40 |
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| 41 | =item B<-f>
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| 42 |
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| 43 | Enable binary output on terminals. Normally, B<opt> will refuse to
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| 44 | write raw bitcode output if the output stream is a terminal. With this option,
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| 45 | B<opt> will write raw bitcode regardless of the output device.
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| 46 |
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| 47 | =item B<-help>
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| 48 |
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| 49 | Print a summary of command line options.
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| 50 |
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| 51 | =item B<-o> I<filename>
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| 52 |
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| 53 | Specify the output filename.
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| 54 |
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| 55 | =item B<-S>
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| 56 |
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| 57 | Write output in LLVM intermediate language (instead of bitcode).
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| 58 |
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| 59 | =item B<-{passname}>
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| 60 |
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| 61 | B<opt> provides the ability to run any of LLVM's optimization or analysis passes
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| 62 | in any order. The B<-help> option lists all the passes available. The order in
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| 63 | which the options occur on the command line are the order in which they are
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| 64 | executed (within pass constraints).
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| 65 |
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| 66 | =item B<-std-compile-opts>
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| 67 |
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| 68 | This is short hand for a standard list of I<compile time optimization> passes.
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| 69 | This is typically used to optimize the output from the llvm-gcc front end. It
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| 70 | might be useful for other front end compilers as well. To discover the full set
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| 71 | of options available, use the following command:
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| 72 |
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| 73 | llvm-as < /dev/null | opt -std-compile-opts -disable-output -debug-pass=Arguments
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| 74 |
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| 75 | =item B<-disable-inlining>
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| 76 |
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| 77 | This option is only meaningful when B<-std-compile-opts> is given. It simply
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| 78 | removes the inlining pass from the standard list.
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| 79 |
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| 80 | =item B<-disable-opt>
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| 81 |
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| 82 | This option is only meaningful when B<-std-compile-opts> is given. It disables
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| 83 | most, but not all, of the B<-std-compile-opts>. The ones that remain are
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| 84 | B<-verify>, B<-lower-setjmp>, and B<-funcresolve>.
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| 85 |
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| 86 | =item B<-strip-debug>
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| 87 |
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| 88 | This option causes opt to strip debug information from the module before
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| 89 | applying other optimizations. It is essentially the same as B<-strip> but it
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| 90 | ensures that stripping of debug information is done first.
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| 91 |
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| 92 | =item B<-verify-each>
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| 93 |
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| 94 | This option causes opt to add a verify pass after every pass otherwise specified
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| 95 | on the command line (including B<-verify>). This is useful for cases where it
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| 96 | is suspected that a pass is creating an invalid module but it is not clear which
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| 97 | pass is doing it. The combination of B<-std-compile-opts> and B<-verify-each>
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| 98 | can quickly track down this kind of problem.
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| 99 |
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| 100 | =item B<-profile-info-file> I<filename>
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| 101 |
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| 102 | Specify the name of the file loaded by the -profile-loader option.
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| 103 |
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| 104 | =item B<-stats>
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| 105 |
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| 106 | Print statistics.
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| 107 |
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| 108 | =item B<-time-passes>
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| 109 |
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| 110 | Record the amount of time needed for each pass and print it to standard
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| 111 | error.
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| 112 |
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| 113 | =item B<-debug>
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| 114 |
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| 115 | If this is a debug build, this option will enable debug printouts
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| 116 | from passes which use the I<DEBUG()> macro. See the B<LLVM Programmer's
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| 117 | Manual>, section I<#DEBUG> for more information.
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| 118 |
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| 119 | =item B<-load>=I<plugin>
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| 120 |
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| 121 | Load the dynamic object I<plugin>. This object should register new optimization
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| 122 | or analysis passes. Once loaded, the object will add new command line options to
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| 123 | enable various optimizations or analyses. To see the new complete list of
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| 124 | optimizations, use the B<-help> and B<-load> options together. For example:
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| 125 |
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| 126 | opt -load=plugin.so -help
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| 127 |
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| 128 | =item B<-p>
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| 129 |
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| 130 | Print module after each transformation.
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| 131 |
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| 132 | =back
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| 133 |
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| 134 | =head1 EXIT STATUS
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| 135 |
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| 136 | If B<opt> succeeds, it will exit with 0. Otherwise, if an error
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| 137 | occurs, it will exit with a non-zero value.
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| 138 |
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| 139 | =head1 AUTHORS
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| 140 |
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| 141 | Maintained by the LLVM Team (L<http://llvm.org/>).
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| 142 |
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| 143 | =cut
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