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197 lines
5.3 KiB
HTML
<html>
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<title>LLVM: gccld tool</title>
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<body bgcolor=white>
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<center><h1>LLVM: <tt>gccld</tt> tool</h1></center>
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<HR>
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<h3>NAME</h3>
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<tt>gccld</tt>
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<h3>SYNOPSIS</h3>
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<tt>gccld [options] < filename> [ filename ...]</tt>
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<h3>DESCRIPTION</h3>
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The <tt>gccld</tt> utility takes a set of LLVM bytecode files and links them
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together into a single LLVM bytecode file. The output bytecode file can be
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another bytecode library or an executable bytecode program. Using additional
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options, <tt>gccld</tt> is able to produce native code executables.
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<p>
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The <tt>gccld</tt> utility is primarily used by the <a href="llvmgcc.html">C</a>
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and <a href="llvmgxx.html">C++</a> front-ends, and as such, attempts to mimic
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the interface provided by the default system linker so that it can act as a
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"drop-in" replacement.
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<p>
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The <tt>gccld</tt> tool performs a small set of interprocedural, post-link,
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optimizations on the program.
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<h4>Search Order</h4>
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<p>
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When looking for objects specified on the command line, <tt>gccld</tt> will
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search for the object first in the current directory and then in the directory
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specified by the <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable. If it
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cannot find the object, it fails.
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</p>
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<p>
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When looking for a library specified with the -l option, <tt>gccld</tt> first
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attempts to load a file with that name from the current directory. If that
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fails, it looks for lib<library>.bc, lib<library>.a, or
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lib<library>.<shared library extension>, in that order, in each
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directory added to the library search path with the -L option. These
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directories are searched in the order they
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were specified. If the library cannot be located, then <tt>gccld</tt> looks in
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the directory specified by the <tt>LLVM_LIB_SEARCH_PATH</tt> environment
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variable. If it does not find a library there, it fails.
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</p>
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<p>
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The shared library extension is usually <tt>.so</tt>, but it may differ
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depending upon the system.
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</p>
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<p>
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The -L option is global. It does not matter where it is specified in the list
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of command line arguments; the directory is simply added to the search path and
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is applied to all libraries, preceding or succeeding, in the command line.
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</p>
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<h4>Link order</h4>
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All object files are linked first in the order they were specified on the
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command line. All library files are linked next. Some libraries may not be
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linked into the object program; see below.
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<h4>Library Linkage</h4>
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Object files and static bytecode objects are always linked into the output
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file. Library archives (.a files) load only the objects within the archive
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that define symbols needed by the output file. Hence, libraries should be
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listed after the object files and libraries which need them; otherwise, the
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library may not be linked in, and the dependent library will not have its
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undefined symbols defined.
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<h4>Native code generation</h4>
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The <tt>gccld</tt> program has limited support for native code generation, when
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using the -native option.
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<h3>OPTIONS</h3>
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<ul>
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<li> -help
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<br>
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Print a summary of command line options.
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<p>
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<li> -o <filename>
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<br>
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Specify the output filename which will hold the linked bytecode.
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<p>
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<li> -stats
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<br>
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Print statistics.
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<p>
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<li> -time-passes
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<br>
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Record the amount of time needed for each pass and print it to standard
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error.
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<p>
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<li> -verify
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<br>
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Verify each pass result.
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<p>
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<li> -disable-opt
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<br>
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Disable all link-time optimization passes.
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<p>
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<li> -L=<directory>
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<br>
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Add directory to the list of directories to search when looking for
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libraries.
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<p>
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<li> -disable-internalize
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<br>
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Do not mark all symbols as internal.
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<p>
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<li> -internalize-public-api-file <filename>
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<br>
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Preserve the list of symbol names in the file filename.
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<p>
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<li> -internalize-public-api-list <list>
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<br>
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Preserve the symbol names in list.
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<p>
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<li> -l=<library>
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<br>
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Specify libraries to include when linking the output file. When
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linking, <tt>gccld</tt> will first attempt to load a file with the
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pathname <tt>library</tt>. If that fails, it will then attempt to load
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lib<library>.bc, lib<library>.a, and
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lib<library>.<shared library extension>, in that order.
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<p>
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<li> -link-as-library
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<br>
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Link the .bc files together as a library, not an executable.
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<p>
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<li> -native
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<br>
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Generate a native, machine code executable.
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<p>
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When generating native executables, <tt>gccld</tt> first checks for a bytecode
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version of the library and links it in, if necessary. If the library is
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missing, <tt>gccld</tt> skips it. Then, <tt>gccld</tt> links in the same
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libraries as native code.
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<p>
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In this way, <tt>gccld</tt> should be able to link in optimized bytecode
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subsets of common libraries and then link in any part of the library that
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hasn't been converted to bytecode.
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<p>
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<li> -s
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<br>
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Strip symbol information from the generated executable.
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<p>
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<li> -v
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<br>
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Print information about actions taken.
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</ul>
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<h3>EXIT STATUS</h3>
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If <tt>gccld</tt> succeeds, it will exit with 0. Otherwise, if an error occurs,
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it will exit with a non-zero value.
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<h3>SEE ALSO</h3>
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<a href="llvm-link.html"><tt>llvm-link</tt></a>
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<a href="gccas.html"><tt>gccas</tt></a>
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<h3>BUGS</h3>
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The -L option cannot be used for find native code libraries when using the
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-native option.
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<HR>
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Maintained by the <a href="http://llvm.cs.uiuc.edu">LLVM Team</a>.
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</body>
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</html>
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