LLVM-LD(1) LLVM Command Guide LLVM-LD(1)NAMEllvm-ld - LLVM linker
SYNOPSISllvm-ld <options> <files>
DESCRIPTION
The 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, llvm-ld is able to produce native code executables.
The 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 llvm-ld tools attempts to mimic the interface provided by the
default system linker so that it can act as a drop-in replacement.
Search Order
When looking for objects specified on the command line, llvm-ld will
search for the object first in the current directory and then in the
directory specified by the LLVM_LIB_SEARCH_PATH environment variable.
If it cannot find the object, it fails.
When looking for a library specified with the -l option, llvm-ld first
attempts to load a file with that name from the current directory. If
that fails, it looks for liblibrary.bc, liblibrary.a, or
liblibrary.shared library extension, in that order, in each directory
added to the library search path with the -L option. These directories
are searched in the order they are specified. If the library cannot be
located, then llvm-ld looks in the directory specified by the
LLVM_LIB_SEARCH_PATH environment variable. If it does not find a
library there, it fails.
The shared library extension may be .so, .dyld, .dll, or something
different, depending upon the system.
The -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.
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.
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.
Native code generation
The llvm-ld program has limited support for native code generation,
when using the -native or -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.
OPTIONS
General Options
-help
Print a summary of command line options.
-v Specifies verbose mode. In this mode the linker will print
additional information about the actions it takes, programs it
executes, etc.
-stats
Print statistics.
-time-passes
Record the amount of time needed for each pass and print it to
standard error.
Input/Output Options
-o filename
This overrides the default output file and specifies the name of
the file that should be generated by the linker. By default, llvm-
ld generates a file named a.out for compatibility with ld. The
output will be written to filename.
-b 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 -o filename option.
-lname
This option specifies the name of a library to search when
resolving symbols for the program. Only the base name should be
specified as name, without a lib prefix or any suffix.
-LPath
This option tells llvm-ld to look in Path to find any library
subsequently specified with the -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 -l option that occur before any -L options will
not search the paths given by the -L options following it.
-link-as-library
Link the bitcode files together as a library, not an executable. In
this mode, undefined symbols will be permitted.
-r An alias for -link-as-library.
-native
Generate a native machine code executable.
When generating native executables, llvm-ld first checks for a
bitcode version of the library and links it in, if necessary. If
the library is missing, llvm-ld skips it. Then, llvm-ld links in
the same libraries as native code.
In this way, 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.
-native-cbe
Generate a native machine code executable with the LLVM C backend.
This option is identical to the -native option, but uses the C
backend to generate code for the program instead of an LLVM native
code generator.
Optimization Options
-disable-inlining
Do not run the inlining pass. Functions will not be inlined into
other functions.
-disable-opt
Completely disable optimization.
-disable-internalize
Do not mark all symbols as internal.
-verify-each
Run the verification pass after each of the passes to verify
intermediate results.
-strip-all
Strip all debug and symbol information from the executable to make
it smaller.
-strip-debug
Strip all debug information from the executable to make it smaller.
-s An alias for -strip-all.
-S An alias for -strip-debug.
-export-dynamic
An alias for -disable-internalize
-post-link-optPath
Run post-link optimization program. After linking is completed a
bitcode file will be generated. It will be passed to the program
specified by 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
EXIT STATUS
If llvm-ld succeeds, it will exit with 0 return code. If an error
occurs, it will exit with a non-zero return code.
ENVIRONMENT
The "LLVM_LIB_SEARCH_PATH" environment variable is used to find bitcode
libraries. Any paths specified in this variable will be searched after
the "-L" options.
SEE ALSO
llvm-link
AUTHORS
Maintained by the LLVM Team (<http://llvm.org/>).
CVS 2011-12-13 LLVM-LD(1)
