docs/CommandGuide/llvm-ld.pod - llvm - Git at Google

 =pod

 =head1 NAME

 llvm-ld - LLVM linker

 =head1 SYNOPSIS

 B<llvm-ld> <options> <files>

 =head1 DESCRIPTION

 The B<llvm-ld> tool takes a set of LLVM bitcode files and links them
 together into a single LLVM bitcode file.  The output bitcode file can be
 another bitcode file or an executable bitcode program.  Using additional
 options, B<llvm-ld> is able to produce native code executables.

 The B<llvm-ld> tool is the main linker for LLVM. It is used to link together
 the output of LLVM front-end compilers and run "link time" optimizations (mostly
 the inter-procedural kind).

 The B<llvm-ld> tools attempts to mimic the interface provided by the default
 system linker so that it can act as a I<drop-in> replacement.

 =head2 Search Order

 When looking for objects specified on the command line, B<llvm-ld> will search
 for the object first in the current directory and then in the directory
 specified by the B<LLVM_LIB_SEARCH_PATH> environment variable.  If it cannot
 find the object, it fails.

 When looking for a library specified with the B<-l> option, B<llvm-ld> first
 attempts to load a file with that name from the current directory.  If that
 fails, it looks for libI<library>.bc, libI<library>.a, or libI<library>.I<shared
 library extension>, in that order, in each directory added to the library search
 path with the B<-L> option.  These directories are searched in the order they
 are specified.  If the library cannot be located, then B<llvm-ld> looks in the
 directory specified by the B<LLVM_LIB_SEARCH_PATH> environment variable.  If it
 does not find a library there, it fails.

 The I<shared library extension> may be I<.so>, I<.dyld>, I<.dll>, or something
 different, depending upon the system.

 The B<-L> option is global.  It does not matter where it is specified in the
 list of command line arguments; the directory is simply added to the search path
 and is applied to all libraries, preceding or succeeding, in the command line.

 =head2 Link order

 All object and bitcode files are linked first in the order they were
 specified on the command line.  All library files are linked next.
 Some libraries may not be linked into the object program; see below.

 =head2 Library Linkage

 Object files and static bitcode objects are always linked into the output
 file.  Library archives (.a files) load only the objects within the archive
 that define symbols needed by the output file.  Hence, libraries should be
 listed after the object files and libraries which need them; otherwise, the
 library may not be linked in, and the dependent library will not have its
 undefined symbols defined.

 =head2 Native code generation

 The B<llvm-ld> program has limited support for native code generation, when
 using the B<-native> or B<-native-cbe> options. Native code generation is
 performed by converting the linked bitcode into native assembly (.s) or C code
 and running the system compiler (typically gcc) on the result.

 =head1 OPTIONS

 =head2 General Options

 =over

 =item B<-help>

 Print a summary of command line options.

 =item B<-v>

 Specifies verbose mode. In this mode the linker will print additional
 information about the actions it takes, programs it executes, etc.

 =item B<-stats>

 Print statistics.

 =item B<-time-passes>

 Record the amount of time needed for each pass and print it to standard
 error.

 =back

 =head2 Input/Output Options

 =over

 =item B<-o> F<filename>

 This overrides the default output file and specifies the name of the file that
 should be generated by the linker. By default, B<llvm-ld> generates a file named
 F<a.out> for compatibility with B<ld>. The output will be written to
 F<filename>.

 =item B<-b> F<filename>

 This option can be used to override the output bitcode file name. By default,
 the name of the bitcode output file is one more ".bc" suffix added to the name
 specified by B<-o filename> option.

 =item B<-l>F<name>

 This option specifies the F<name> of a library to search when resolving symbols
 for the program. Only the base name should be specified as F<name>, without a
 F<lib> prefix or any suffix.

 =item B<-L>F<Path>

 This option tells B<llvm-ld> to look in F<Path> to find any library subsequently
 specified with the B<-l> option. The paths will be searched in the order in
 which they are specified on the command line. If the library is still not found,
 a small set of system specific directories will also be searched. Note that
 libraries specified with the B<-l> option that occur I<before> any B<-L> options
 will not search the paths given by the B<-L> options following it.

 =item B<-link-as-library>

 Link the bitcode files together as a library, not an executable. In this mode,
 undefined symbols will be permitted.

 =item B<-r>

 An alias for -link-as-library.

 =item B<-native>

 Generate a native machine code executable.

 When generating native executables, B<llvm-ld> first checks for a bitcode
 version of the library and links it in, if necessary.  If the library is
 missing, B<llvm-ld> skips it.  Then, B<llvm-ld> links in the same
 libraries as native code.

 In this way, B<llvm-ld> should be able to link in optimized bitcode
 subsets of common libraries and then link in any part of the library that
 hasn't been converted to bitcode.

 =item B<-native-cbe>

 Generate a native machine code executable with the LLVM C backend.

 This option is identical to the B<-native> option, but uses the
 C backend to generate code for the program instead of an LLVM native
 code generator.

 =back

 =head2 Optimization Options

 =over

 =item B<-disable-inlining>

 Do not run the inlining pass. Functions will not be inlined into other
 functions.

 =item B<-disable-opt>

 Completely disable optimization.

 =item B<-disable-internalize>

 Do not mark all symbols as internal.

 =item B<-verify-each>

 Run the verification pass after each of the passes to verify intermediate
 results.

 =item B<-strip-all>

 Strip all debug and symbol information from the executable to make it smaller.

 =item B<-strip-debug>

 Strip all debug information from the executable to make it smaller.

 =item B<-s>

 An alias for B<-strip-all>.

 =item B<-S>

 An alias for B<-strip-debug>.

 =item B<-export-dynamic>

 An alias for B<-disable-internalize>

 =item B<-post-link-opt>F<Path>

 Run post-link optimization program. After linking is completed a bitcode file
 will be generated. It will be passed to the program specified by F<Path> as the
 first argument. The second argument to the program will be the name of a
 temporary file into which the program should place its optimized output. For
 example, the "no-op optimization" would be a simple shell script:

     #!/bin/bash
     cp $1 $2

 =back

 =head1 EXIT STATUS

 If B<llvm-ld> succeeds, it will exit with 0 return code.  If an error occurs,
 it will exit with a non-zero return code.

 =head1 ENVIRONMENT

 The C<LLVM_LIB_SEARCH_PATH> environment variable is used to find bitcode
 libraries. Any paths specified in this variable will be searched after the C<-L>
 options.

 =head1 SEE ALSO

 L<llvm-link|llvm-link>

 =head1 AUTHORS

 Maintained by the LLVM Team (L<http://llvm.org>).

 =cut
	=pod

	=head1 NAME

	llvm-ld - LLVM linker

	=head1 SYNOPSIS

	B<llvm-ld> <options> <files>

	=head1 DESCRIPTION

	The B<llvm-ld> tool takes a set of LLVM bitcode files and links them
	together into a single LLVM bitcode file. The output bitcode file can be
	another bitcode file or an executable bitcode program. Using additional
	options, B<llvm-ld> is able to produce native code executables.

	The B<llvm-ld> tool is the main linker for LLVM. It is used to link together
	the output of LLVM front-end compilers and run "link time" optimizations (mostly
	the inter-procedural kind).

	The B<llvm-ld> tools attempts to mimic the interface provided by the default
	system linker so that it can act as a I<drop-in> replacement.

	=head2 Search Order

	When looking for objects specified on the command line, B<llvm-ld> will search
	for the object first in the current directory and then in the directory
	specified by the B<LLVM_LIB_SEARCH_PATH> environment variable. If it cannot
	find the object, it fails.

	When looking for a library specified with the B<-l> option, B<llvm-ld> first
	attempts to load a file with that name from the current directory. If that
	fails, it looks for libI<library>.bc, libI<library>.a, or libI<library>.I<shared
	library extension>, in that order, in each directory added to the library search
	path with the B<-L> option. These directories are searched in the order they
	are specified. If the library cannot be located, then B<llvm-ld> looks in the
	directory specified by the B<LLVM_LIB_SEARCH_PATH> environment variable. If it
	does not find a library there, it fails.

	The I<shared library extension> may be I<.so>, I<.dyld>, I<.dll>, or something
	different, depending upon the system.

	The B<-L> option is global. It does not matter where it is specified in the
	list of command line arguments; the directory is simply added to the search path
	and is applied to all libraries, preceding or succeeding, in the command line.

	=head2 Link order

	All object and bitcode files are linked first in the order they were
	specified on the command line. All library files are linked next.
	Some libraries may not be linked into the object program; see below.

	=head2 Library Linkage

	Object files and static bitcode objects are always linked into the output
	file. Library archives (.a files) load only the objects within the archive
	that define symbols needed by the output file. Hence, libraries should be
	listed after the object files and libraries which need them; otherwise, the
	library may not be linked in, and the dependent library will not have its
	undefined symbols defined.

	=head2 Native code generation

	The B<llvm-ld> program has limited support for native code generation, when
	using the B<-native> or B<-native-cbe> options. Native code generation is
	performed by converting the linked bitcode into native assembly (.s) or C code
	and running the system compiler (typically gcc) on the result.

	=head1 OPTIONS

	=head2 General Options

	=over

	=item B<-help>

	Print a summary of command line options.

	=item B<-v>

	Specifies verbose mode. In this mode the linker will print additional
	information about the actions it takes, programs it executes, etc.

	=item B<-stats>

	Print statistics.

	=item B<-time-passes>

	Record the amount of time needed for each pass and print it to standard
	error.

	=back

	=head2 Input/Output Options

	=over

	=item B<-o> F<filename>

	This overrides the default output file and specifies the name of the file that
	should be generated by the linker. By default, B<llvm-ld> generates a file named
	F<a.out> for compatibility with B<ld>. The output will be written to
	F<filename>.

	=item B<-b> F<filename>

	This option can be used to override the output bitcode file name. By default,
	the name of the bitcode output file is one more ".bc" suffix added to the name
	specified by B<-o filename> option.

	=item B<-l>F<name>

	This option specifies the F<name> of a library to search when resolving symbols
	for the program. Only the base name should be specified as F<name>, without a
	F<lib> prefix or any suffix.

	=item B<-L>F<Path>

	This option tells B<llvm-ld> to look in F<Path> to find any library subsequently
	specified with the B<-l> option. The paths will be searched in the order in
	which they are specified on the command line. If the library is still not found,
	a small set of system specific directories will also be searched. Note that
	libraries specified with the B<-l> option that occur I<before> any B<-L> options
	will not search the paths given by the B<-L> options following it.

	=item B<-link-as-library>

	Link the bitcode files together as a library, not an executable. In this mode,
	undefined symbols will be permitted.

	=item B<-r>

	An alias for -link-as-library.

	=item B<-native>

	Generate a native machine code executable.

	When generating native executables, B<llvm-ld> first checks for a bitcode
	version of the library and links it in, if necessary. If the library is
	missing, B<llvm-ld> skips it. Then, B<llvm-ld> links in the same
	libraries as native code.

	In this way, B<llvm-ld> should be able to link in optimized bitcode
	subsets of common libraries and then link in any part of the library that
	hasn't been converted to bitcode.

	=item B<-native-cbe>

	Generate a native machine code executable with the LLVM C backend.

	This option is identical to the B<-native> option, but uses the
	C backend to generate code for the program instead of an LLVM native
	code generator.

	=back

	=head2 Optimization Options

	=over

	=item B<-disable-inlining>

	Do not run the inlining pass. Functions will not be inlined into other
	functions.

	=item B<-disable-opt>

	Completely disable optimization.

	=item B<-disable-internalize>

	Do not mark all symbols as internal.

	=item B<-verify-each>

	Run the verification pass after each of the passes to verify intermediate
	results.

	=item B<-strip-all>

	Strip all debug and symbol information from the executable to make it smaller.

	=item B<-strip-debug>

	Strip all debug information from the executable to make it smaller.

	=item B<-s>

	An alias for B<-strip-all>.

	=item B<-S>

	An alias for B<-strip-debug>.

	=item B<-export-dynamic>

	An alias for B<-disable-internalize>

	=item B<-post-link-opt>F<Path>

	Run post-link optimization program. After linking is completed a bitcode file
	will be generated. It will be passed to the program specified by F<Path> as the
	first argument. The second argument to the program will be the name of a
	temporary file into which the program should place its optimized output. For
	example, the "no-op optimization" would be a simple shell script:

	#!/bin/bash
	cp $1 $2

	=back

	=head1 EXIT STATUS

	If B<llvm-ld> succeeds, it will exit with 0 return code. If an error occurs,
	it will exit with a non-zero return code.

	=head1 ENVIRONMENT

	The C<LLVM_LIB_SEARCH_PATH> environment variable is used to find bitcode
	libraries. Any paths specified in this variable will be searched after the C<-L>
	options.

	=head1 SEE ALSO

	L<llvm-link\|llvm-link>

	=head1 AUTHORS

	Maintained by the LLVM Team (L<http://llvm.org>).

	=cut