diff options
author | Anton Korobeynikov <asl@math.spbu.ru> | 2008-05-04 06:19:55 +0000 |
---|---|---|
committer | Anton Korobeynikov <asl@math.spbu.ru> | 2008-05-04 06:19:55 +0000 |
commit | cae8ccd12d62a89a3c539ecb549a91a976f7f7b2 (patch) | |
tree | ea8de6f2e345d80c3ee1ce2c4ccf11e67904dd1b /docs/CommandGuide | |
parent | a9d9ca469fd2442e1352028a7a69d23de0a4cbd5 (diff) | |
download | external_llvm-cae8ccd12d62a89a3c539ecb549a91a976f7f7b2.zip external_llvm-cae8ccd12d62a89a3c539ecb549a91a976f7f7b2.tar.gz external_llvm-cae8ccd12d62a89a3c539ecb549a91a976f7f7b2.tar.bz2 |
Drop llvmc also, it will be replaced by shiny new llvmc2
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50615 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/CommandGuide')
-rw-r--r-- | docs/CommandGuide/llvmc.pod | 431 |
1 files changed, 0 insertions, 431 deletions
diff --git a/docs/CommandGuide/llvmc.pod b/docs/CommandGuide/llvmc.pod deleted file mode 100644 index 5e6cc95..0000000 --- a/docs/CommandGuide/llvmc.pod +++ /dev/null @@ -1,431 +0,0 @@ -=pod - -=head1 NAME - -llvmc - The LLVM Compiler Driver (experimental) - -=head1 SYNOPSIS - -B<llvmc> [I<options>] [I<filenames>...] - -=head1 DESCRIPTION - -B<llvmc> is a configurable driver for invoking other LLVM (and non-LLVM) tools -in order to compile, optimize and link software for multiple languages. For -those familiar with FSF's B<gcc> tool, it is very similar. Please note that -B<llvmc> is considered an experimental tool. B<llvmc> has the following goals: - -=over - -=item * provide a single point of access to the LLVM tool set, - -=item * hide the complexities of the LLVM tools through a single interface, - -=item * make integration of existing non-LLVM tools simple, - -=item * extend the capabilities of minimal front ends, and - -=item * make the interface for compiling consistent for all languages. - -=back - -The tool itself does nothing with a user's program. It merely invokes other -tools to get the compilation tasks done. - -The options supported by B<llvmc> generalize the compilation process and -provide a consistent and simple interface for multiple programming languages. -This makes it easier for developers to get their software compiled with LLVM. -Without B<llvmc>, developers would need to understand how to invoke the -front-end compiler, optimizer, assembler, and linker in order to compile their -programs. B<llvmc>'s sole mission is to trivialize that process. - -=head2 Basic Operation - -B<llvmc> always takes the following basic actions: - -=over - -=item * Command line options and filenames are collected. - -The command line options provide the marching orders to B<llvmc> on what actions -it should perform. This is the I<request> the user is making of B<llvmc> and it -is interpreted first. - -=item * Configuration files are read. - -Based on the options and the suffixes of the filenames presented, a set of -configuration files are read to configure the actions B<llvmc> will take. -Configuration files are provided by either LLVM or the front end compiler tools -that B<llvmc> invokes. Users generally don't need to be concerned with the -contents of the configuration files. - -=item * Determine actions to take. - -The tool chain needed to complete the task is determined. This is the primary -work of B<llvmc>. It breaks the request specified by the command line options -into a set of basic actions to be done: - -=over - -=item * Pre-processing: gathering/filtering compiler input (optional). - -=item * Translation: source language to bitcode conversion. - -=item * Assembly: bitcode to native code conversion. - -=item * Optimization: conversion of bitcode to something that runs faster. - -=item * Linking: combining multiple bitcode files to produce executable program. - -=back - -=item * Execute actions. - -The actions determined previously are executed sequentially and then -B<llvmc> terminates. - -=back - -=head1 OPTIONS - -=head2 Control Options - -Control options tell B<llvmc> what to do at a high level. The -following control options are defined: - -=over - -=item B<-c> or B<--compile> - -This option specifies that the linking phase is not to be run. All -previous phases, if applicable will run. This is generally how a given -bitcode file is compiled and optimized for a source language module. - -=item B<-k> or B<--link> or default - -This option (or the lack of any control option) specifies that all stages -of compilation, optimization, and linking should be attempted. Source files -specified on the command line will be compiled and linked with objects and -libraries also specified. - -=item B<-S> - -This option specifies that compilation should end in the creation of -an LLVM assembly file that can be later converted to an LLVM object -file. - -=item B<-E> - -This option specifies that no compilation or linking should be -performed. Only pre-processing, if applicable to the language being -compiled, is performed. For languages that support it, this will -result in the output containing the raw input to the compiler. - -=back - -=head2 Optimization Options - -Optimization with B<llvmc> is based on goals and specified with -the following -O options. The specific details of which -optimizations run is controlled by the configuration files because -each source language will have different needs. - -=over - -=item B<-O1> or B<-O0> (default, fast compilation) - -Only those optimizations that will hasten the compilation (mostly by reducing -the output) are applied. In general these are extremely fast and simple -optimizations that reduce emitted code size. The goal here is not to make the -resulting program fast but to make the compilation fast. If not specified, -this is the default level of optimization. - -=item B<-O2> (basic optimization) - -This level of optimization specifies a balance between generating good code -that will execute reasonably quickly and not spending too much time optimizing -the code to get there. For example, this level of optimization may include -things like global common sub-expression elimination, aggressive dead code -elimination, and scalar replication. - -=item B<-O3> (aggressive optimization) - -This level of optimization aggressively optimizes each set of files compiled -together. However, no link-time inter-procedural optimization is performed. -This level implies all the optimizations of the B<-O1> and B<-O2> optimization -levels, and should also provide loop optimizations and compile time -inter-procedural optimizations. Essentially, this level tries to do as much -as it can with the input it is given but doesn't do any link time IPO. - -=item B<-O4> (link time optimization) - -In addition to the previous three levels of optimization, this level of -optimization aggressively optimizes each program at link time. It employs -basic analysis and basic link-time inter-procedural optimizations, -considering the program as a whole. - -=item B<-O5> (aggressive link time optimization) - -This is the same as B<-O4> except it employs aggressive analyses and -aggressive inter-procedural optimization. - -=item B<-O6> (profile guided optimization: not implemented) - -This is the same as B<-O5> except that it employs profile-guided -re-optimization of the program after it has executed. Note that this implies -a single level of re-optimization based on run time profile analysis. Once -the re-optimization has completed, the profiling instrumentation is -removed and final optimizations are employed. - -=item B<-O7> (lifelong optimization: not implemented) - -This is the same as B<-O5> and similar to B<-O6> except that re-optimization -is performed through the life of the program. That is, each run will update -the profile by which future re-optimizations are directed. - -=back - -=head2 Input Options - -=over - -=item B<-l> I<LIBRARY> - -This option instructs B<llvmc> to locate a library named I<LIBRARY> and search -it for unresolved symbols when linking the program. - -=item B<-L> F<path> - -This option instructs B<llvmc> to add F<path> to the list of places in which -the linker will - -=item B<-x> I<LANGUAGE> - -This option instructs B<llvmc> to regard the following input files as -containing programs in the language I<LANGUAGE>. Normally, input file languages -are identified by their suffix but this option will override that default -behavior. The B<-x> option stays in effect until the end of the options or -a new B<-x> option is encountered. - -=back - -=head2 Output Options - -=over - -=item B<-m>I<arch> - -This option selects the back end code generator to use. The I<arch> portion -of the option names the back end to use. - -=item B<--native> - -Normally, B<llvmc> produces bitcode files at most stages of compilation. -With this option, B<llvmc> will arrange for native object files to be -generated with the B<-c> option, native assembly files to be generated -with the B<-S> option, and native executables to be generated with the -B<--link> option. In the case of the B<-E> option, the output will not -differ as there is no I<native> version of pre-processed output. - -=item B<-o> F<filename> - -Specify the output file name. The contents of the file depend on other -options. - -=back - -=head2 Information Options - -=over - -=item B<-n> or B<--no-op> - -This option tells B<llvmc> to do everything but actually execute the -resulting tools. In combination with the B<-v> option, this causes B<llvmc> -to merely print out what it would have done. - -=item B<-v> or B<--verbose> - -This option will cause B<llvmc> to print out (on standard output) each of the -actions it takes to accomplish the objective. The output will immediately -precede the invocation of other tools. - -=item B<--stats> - -Print all statistics gathered during the compilation to the standard error. -Note that this option is merely passed through to the sub-tools to do with -as they please. - -=item B<--time-passes> - -Record the amount of time needed for each optimization pass and print it -to standard error. Like B<--stats> this option is just passed through to -the sub-tools to do with as they please. - -=item B<--time-programs> - -Record the amount of time each program (compilation tool) takes and print -it to the standard error. - -=back - -=head2 Language Specific Options - -=over - -=item B<-T,pre>=I<options> - -Pass an arbitrary option to the pre-processor. - -=item B<-T,opt>=I<options> - -Pass an arbitrary option to the optimizer. - -=item B<-T,lnk>=I<options> - -Pass an arbitrary option to the linker. - -=item B<-T,asm>=I<options> - -Pass an arbitrary option to the code generator. - -=back - -=head2 C/C++ Specific Options - -=over - -=item B<-I>F<path> - -This option is just passed through to a C or C++ front end compiler to tell it -where include files can be found. - -=item B<-D>F<symbol> - -This option is just passed through to a C or C++ front end compiler to tell it -to define a symbol. - -=back - -=head2 Miscellaneous Options - -=over - -=item B<--help> - -Print a summary of command line options. - -=item B<--version> - -This option will cause B<llvmc> to print out its version number and terminate. - -=back - -=head2 Advanced Options - -You better know what you're doing if you use these options. Improper use -of these options can produce drastically wrong results. - -=over - -=item B<--config-dir> F<dirname> - -This option tells B<llvmc> to read configuration data from the I<directory> -named F<dirname>. Data from such directories will be read in the order -specified on the command line after all other standard configuration files have -been read. This allows users or groups of users to conveniently create -their own configuration directories in addition to the standard ones to which -they may not have write access. - -=back - - -=head2 Unimplemented Options - -The options below are not currently implemented in B<llvmc> but will be -eventually. They are documented here as "future design". - -=over - -=item B<--show-config> I<[suffixes...]> - -When this option is given, the only action taken by B<llvmc> is to show its -final configuration state in the form of a configuration file. No compilation -tasks will be conducted when this option is given; processing will stop once -the configuration has been printed. The optional (comma separated) list of -suffixes controls what is printed. Without any suffixes, the configuration -for all languages is printed. With suffixes, only the languages pertaining -to those file suffixes will be printed. The configuration information is -printed after all command line options and configuration files have been -read and processed. This allows the user to verify that the correct -configuration data has been read by B<llvmc>. - -=item B<--config> :I<section>:I<name>=I<value> - -This option instructs B<llvmc> to accept I<value> as the value for configuration -item I<name> in the section named I<section>. This is a quick way to override -a configuration item on the command line without resorting to changing the -configuration files. - -=item B<--config-only-from> F<dirname> - -This option tells B<llvmc> to skip the normal processing of configuration -files and only configure from the contents of the F<dirname> directory. Multiple -B<--config-only-from> options may be given in which case the directories are -read in the order given on the command line. - -=item B<--emit-raw-code> - -No optimization is done whatsoever. The compilers invoked by B<llvmc> with -this option given will be instructed to produce raw, unoptimized code. This -option is useful only to front end language developers and therefore does not -participate in the list of B<-O> options. This is distinctly different from -the B<-O0> option (a synonym for B<-O1>) because those optimizations will -reduce code size to make compilation faster. With B<--emit-raw-code>, only -the full raw code produced by the compiler will be generated. - -=back - - -=head1 EXIT STATUS - -If B<llvmc> succeeds, it will exit with 0. Otherwise, if an error -occurs, it will exit with a non-zero value and no compilation actions -will be taken. If one of the compilation tools returns a non-zero -status, pending actions will be discarded and B<llvmc> will return the -same result code as the failing compilation tool. - -=head1 DEFICIENCIES - -B<llvmc> is considered an experimental LLVM tool because it has these -deficiencies: - -=over - -=item Insufficient support for native linking - -Because B<llvm-ld> doesn't handle native linking, neither can B<llvmc> - -=item Poor configuration support - -The support for configuring new languages, etc. is weak. There are many -command line configurations that cannot be achieved with the current -support. Furthermore the grammar is cumbersome for configuration files. -Please see L<http://llvm.org/PR686> for further details. - -=item Does not handle target specific configurations - -This is one of the major deficiencies, also addressed in -L<http://llvm.org/PR686> - -=back - -=head1 SEE ALSO - -L<llvm-as|llvm-as>, L<llvm-dis|llvm-dis>, L<llc|llc>, L<llvm-link|llvm-link> - -=head1 AUTHORS - -Maintained by the LLVM Team (L<http://llvm.org>). - -=cut |