=head1 NAME
-llvmc - The LLVM Compiler Driver
+llvmc - The LLVM Compiler Driver (experimental)
=head1 SYNOPSIS
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. B<llvmc> has the
-following goals:
+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 * Pre-processing: gathering/filtering compiler input (optional).
-=item * Translation: source language to bytecode conversion.
+=item * Translation: source language to bitcode conversion.
-=item * Assembly: bytecode to native code conversion.
+=item * Assembly: bitcode to native code conversion.
-=item * Optimization: conversion of bytecode to something that runs faster.
+=item * Optimization: conversion of bitcode to something that runs faster.
-=item * Linking: combining multiple bytecodes to produce executable program.
+=item * Linking: combining multiple bitcode files to produce executable program.
=back
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
-bytecode file is compiled and optimized for a source language module.
+bitcode file is compiled and optimized for a source language module.
=item B<-k> or B<--link> or default
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 subexpression elimination, aggressive dead code
+things like global common sub-expression elimination, aggressive dead code
elimination, and scalar replication.
=item B<-O3> (aggressive optimization)
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 runtime profile analysis. Once
+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<--native>
-Normally, B<llvmc> produces bytecode files at most stages of compilation.
+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
their own configuration directories in addition to the standard ones to which
they may not have write access.
+=back
+
=head2 Unimplemented Options
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<gccas|gccas>, L<gccld|gccld>, L<llvm-as|llvm-as>, L<llvm-dis|llvm-dis>,
-L<llc|llc>, L<llvm-link|llvm-link>
+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.cs.uiuc.edu>).
+Maintained by the LLVM Team (L<http://llvm.org>).
=cut
projects / oota-llvm.git / blobdiff