1LLVM-LD(1) LLVM Command Guide LLVM-LD(1)
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6 llvm-ld - LLVM linker
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9 llvm-ld <options> <files>
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12 The llvm-ld tool takes a set of LLVM bitcode files and links them
13 together into a single LLVM bitcode file. The output bitcode file can
14 be another bitcode file or an executable bitcode program. Using
15 additional options, llvm-ld is able to produce native code executables.
16 The llvm-ld tool is the main linker for LLVM. It is used to link
18 together the output of LLVM front-end compilers and run "link time"
19 optimizations (mostly the inter-procedural kind).
20 The llvm-ld tools attempts to mimic the interface provided by the
22 default system linker so that it can act as a drop-in replacement.
23 Search Order
25 When looking for objects specified on the command line, llvm-ld will
26 search for the object first in the current directory and then in the
27 directory specified by the LLVM_LIB_SEARCH_PATH environment variable.
28 If it cannot find the object, it fails.
29 When looking for a library specified with the -l option, llvm-ld first
31 attempts to load a file with that name from the current directory. If
32 that fails, it looks for liblibrary.bc, liblibrary.a, or
33 liblibrary.shared library extension, in that order, in each directory
34 added to the library search path with the -L option. These directories
35 are searched in the order they are specified. If the library cannot be
36 located, then llvm-ld looks in the directory specified by the
37 LLVM_LIB_SEARCH_PATH environment variable. If it does not find a
38 library there, it fails.
39 The shared library extension may be .so, .dyld, .dll, or something
41 different, depending upon the system.
42 The -L option is global. It does not matter where it is specified in
44 the list of command line arguments; the directory is simply added to
45 the search path and is applied to all libraries, preceding or
46 succeeding, in the command line.
47 Link order
49 All object and bitcode files are linked first in the order they were
50 specified on the command line. All library files are linked next.
51 Some libraries may not be linked into the object program; see below.
52 Library Linkage
54 Object files and static bitcode objects are always linked into the
55 output file. Library archives (.a files) load only the objects within
56 the archive that define symbols needed by the output file. Hence,
57 libraries should be listed after the object files and libraries which
58 need them; otherwise, the library may not be linked in, and the
59 dependent library will not have its undefined symbols defined.
60 Native code generation
62 The llvm-ld program has limited support for native code generation,
63 when using the -native or -native-cbe options. Native code generation
64 is performed by converting the linked bitcode into native assembly (.s)
65 or C code and running the system compiler (typically gcc) on the
66 result.
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69 General Options
70 -help
71 Print a summary of command line options.
72 -v Specifies verbose mode. In this mode the linker will print
74 additional information about the actions it takes, programs it
75 executes, etc.
76 -stats
78 Print statistics.
79 -time-passes
81 Record the amount of time needed for each pass and print it to
82 standard error.
83 Input/Output Options
85 -o filename
86 This overrides the default output file and specifies the name of
87 the file that should be generated by the linker. By default, llvm-
88 ld generates a file named a.out for compatibility with ld. The
89 output will be written to filename.
90 -b filename
92 This option can be used to override the output bitcode file name.
93 By default, the name of the bitcode output file is one more ".bc"
94 suffix added to the name specified by -o filename option.
95 -lname
97 This option specifies the name of a library to search when
98 resolving symbols for the program. Only the base name should be
99 specified as name, without a lib prefix or any suffix.
100 -LPath
102 This option tells llvm-ld to look in Path to find any library
103 subsequently specified with the -l option. The paths will be
104 searched in the order in which they are specified on the command
105 line. If the library is still not found, a small set of system
106 specific directories will also be searched. Note that libraries
107 specified with the -l option that occur before any -L options will
108 not search the paths given by the -L options following it.
109 -link-as-library
111 Link the bitcode files together as a library, not an executable. In
112 this mode, undefined symbols will be permitted.
113 -r An alias for -link-as-library.
115 -native
117 Generate a native machine code executable.
118 When generating native executables, llvm-ld first checks for a
120 bitcode version of the library and links it in, if necessary. If
121 the library is missing, llvm-ld skips it. Then, llvm-ld links in
122 the same libraries as native code.
123 In this way, llvm-ld should be able to link in optimized bitcode
125 subsets of common libraries and then link in any part of the
126 library that hasn't been converted to bitcode.
127 -native-cbe
129 Generate a native machine code executable with the LLVM C backend.
130 This option is identical to the -native option, but uses the C
132 backend to generate code for the program instead of an LLVM native
133 code generator.
134 Optimization Options
136 -disable-inlining
137 Do not run the inlining pass. Functions will not be inlined into
138 other functions.
139 -disable-opt
141 Completely disable optimization.
142 -disable-internalize
144 Do not mark all symbols as internal.
145 -verify-each
147 Run the verification pass after each of the passes to verify
148 intermediate results.
149 -strip-all
151 Strip all debug and symbol information from the executable to make
152 it smaller.
153 -strip-debug
155 Strip all debug information from the executable to make it smaller.
156 -s An alias for -strip-all.
158 -S An alias for -strip-debug.
160 -export-dynamic
162 An alias for -disable-internalize
163 -post-link-optPath
165 Run post-link optimization program. After linking is completed a
166 bitcode file will be generated. It will be passed to the program
167 specified by Path as the first argument. The second argument to the
168 program will be the name of a temporary file into which the program
169 should place its optimized output. For example, the "no-op
170 optimization" would be a simple shell script:
171 #!/bin/bash
173 cp $1 $2
174
176 If llvm-ld succeeds, it will exit with 0 return code. If an error
177 occurs, it will exit with a non-zero return code.
178
180 The "LLVM_LIB_SEARCH_PATH" environment variable is used to find bitcode
181 libraries. Any paths specified in this variable will be searched after
182 the "-L" options.
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185 llvm-link
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188 Maintained by the LLVM Team (<http://llvm.org>).
189CVS 2010-05-07 LLVM-LD(1)