[tools] Add option to create binutils symlinks

[smeenai]

Summary

The LLVM tools can be used as a replacement for binutils, in which case
it's convenient to create symlinks with the binutils names. Add support
for these symlinks in the build system. As with any other llvm tool
symlinks, the user can limit the installed symlinks by only adding the
desired ones to LLVM_TOOLCHAIN_TOOLS.

I'm not the biggest fan of the name LLVM_CREATE_BINUTILS_SYMLINKS, but
it's the best one that came to mind right now. Better name suggestions
would be appreciated.

[smeenai]

@jakehehrlich I see you got that Herald rule set up :)

[compnerd]

I like where this is going, but I think that we want this to be done via an option in the top-level CMakeLists.txt similar to things like LLVM_INSTALL_UTILS.

[smeenai]

Add option and documentation

[smeenai]

I'm wondering if LLVM_INSTALL_BINUTILS_SYMLINKS would be a better name. I went with "create" instead of "install" initially because this option will create the symlinks in the build tree in addition to the install tree, and "install" doesn't convey that fully, but I think most people would care a lot more about the installation part.

[compnerd]

Yeah, I think that INSTALL is a better verb here than CREATE. LG w/ s/CREATE/INSTALL/.

[smeenai]

Rename from CREATE to INSTALL

CMakeLists.txt

set(CMAKE_MODULE_PATH
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
   )
 
 # Generate a CompilationDatabase (compile_commands.json file) for our build,
 # for use by clang_complete, YouCompleteMe, etc.
 set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
 
+option(LLVM_CREATE_BINUTILS_SYMLINKS
+  "Create symlinks from the binutils tool names to the corresponding LLVM tools." OFF)
+
 option(LLVM_INSTALL_UTILS "Include utility binaries in the 'install' target." OFF)
 
 option(LLVM_INSTALL_TOOLCHAIN_ONLY "Only include toolchain files in the 'install' target." OFF)
 
 option(LLVM_USE_FOLDERS "Enable solution folders in Visual Studio. Disable for Express versions." ON)
 if ( LLVM_USE_FOLDERS )
   set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 endif()

docs/CMake.rst

**LLVM_BUILD_TOOLS**:BOOL
   in any case. You can build a tool separately by invoking its target. For
   example, you can build *llvm-as* with a Makefile-based system by executing *make
   llvm-as* at the root of your build directory.
 
 **LLVM_INCLUDE_TOOLS**:BOOL
   Generate build targets for the LLVM tools. Defaults to ON. You can use this
   option to disable the generation of build targets for the LLVM tools.
 
+**LLVM_CREATE_BINUTILS_SYMLINKS**:BOOL
+  Install symlinks from the binutils tool names to the corresponding LLVM tools.
+  For example, ar will be symlinked to llvm-ar.
+
 **LLVM_BUILD_EXAMPLES**:BOOL
   Build LLVM examples. Defaults to OFF. Targets for building each example are
   generated in any case. See documentation for *LLVM_BUILD_TOOLS* above for more
   details.
 
 **LLVM_INCLUDE_EXAMPLES**:BOOL
   Generate build targets for the LLVM examples. Defaults to ON. You can use this
   option to disable the generation of build targets for the LLVM examples.

tools/llvm-ar/CMakeLists.txt

add_llvm_tool(llvm-ar
 
   DEPENDS
   intrinsics_gen
   )
 
 add_llvm_tool_symlink(llvm-ranlib llvm-ar)
 add_llvm_tool_symlink(llvm-lib llvm-ar)
 add_llvm_tool_symlink(llvm-dlltool llvm-ar)
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(ar llvm-ar)
+  add_llvm_tool_symlink(dlltool llvm-ar)
+  add_llvm_tool_symlink(ranlib llvm-ar)
+endif()

tools/llvm-cxxfilt/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Demangle
   Support
   )
 
 add_llvm_tool(llvm-cxxfilt
   llvm-cxxfilt.cpp
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(c++filt llvm-cxxfilt)
+endif()

tools/llvm-dwp/CMakeLists.txt

 
 add_llvm_tool(llvm-dwp
   llvm-dwp.cpp
   DWPError.cpp
 
   DEPENDS
   intrinsics_gen
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(dwp llvm-dwp)
+endif()

tools/llvm-nm/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   AllTargetsAsmParsers
   AllTargetsDescs
   AllTargetsInfos
   Core
   Demangle
   Object
   Support
   )
 
 add_llvm_tool(llvm-nm
   llvm-nm.cpp
 
   DEPENDS
   intrinsics_gen
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(nm llvm-nm)
+endif()

tools/llvm-objcopy/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Object
   Support
   MC
   )
 add_llvm_tool(llvm-objcopy
   llvm-objcopy.cpp
   Object.cpp
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(objcopy llvm-objcopy)
+endif()

tools/llvm-objdump/CMakeLists.txt

add_llvm_tool(llvm-objdump
   ELFDump.cpp
   MachODump.cpp
   WasmDump.cpp
   )
 
 if(HAVE_LIBXAR)
   target_link_libraries(llvm-objdump ${XAR_LIB})
 endif()
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(objdump llvm-objdump)
+endif()

tools/llvm-readobj/CMakeLists.txt

add_llvm_tool(llvm-readobj
   MachODumper.cpp
   ObjDumper.cpp
   WasmDumper.cpp
   Win64EHDumper.cpp
   WindowsResourceDumper.cpp
   )
 
 add_llvm_tool_symlink(llvm-readelf llvm-readobj)
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(readelf llvm-readobj)
+endif()

tools/llvm-size/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Object
   Support
   )
 
 add_llvm_tool(llvm-size
   llvm-size.cpp
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(size llvm-size)
+endif()

tools/llvm-strings/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Core
   Object
   Support
   )
 
 add_llvm_tool(llvm-strings
   llvm-strings.cpp
   )
 
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(strings llvm-strings)
+endif()

tools/llvm-symbolizer/CMakeLists.txt

 # FIXME: As we plan to execute llvm-symbolizer binary from compiler-rt
 # libraries, it has to be compiled for all supported targets (x86_64, i386 etc).
 # This means that we need LLVM libraries to be compiled for these
 # targets as well. Currently, there is no support for such a build strategy.
 
 set(LLVM_LINK_COMPONENTS
   DebugInfoDWARF
   DebugInfoPDB
   Object
   Support
   Symbolize
   )
 
 add_llvm_tool(llvm-symbolizer
   llvm-symbolizer.cpp
   )
+
+if(LLVM_CREATE_BINUTILS_SYMLINKS)
+  add_llvm_tool_symlink(addr2line llvm-symbolizer)
+endif()