1# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
2# file Copyright.txt or https://cmake.org/licensing for details.
3
4#[=======================================================================[.rst:
5CheckIPOSupported
6-----------------
7
8.. versionadded:: 3.9
9
10Check whether the compiler supports an interprocedural optimization (IPO/LTO).
11Use this before enabling the :prop_tgt:`INTERPROCEDURAL_OPTIMIZATION` target
12property.
13
14.. command:: check_ipo_supported
15
16  ::
17
18    check_ipo_supported([RESULT <result>] [OUTPUT <output>]
19                        [LANGUAGES <lang>...])
20
21  Options are:
22
23  ``RESULT <result>``
24    Set ``<result>`` variable to ``YES`` if IPO is supported by the
25    compiler and ``NO`` otherwise.  If this option is not given then
26    the command will issue a fatal error if IPO is not supported.
27  ``OUTPUT <output>``
28    Set ``<output>`` variable with details about any error.
29  ``LANGUAGES <lang>...``
30    Specify languages whose compilers to check.
31    Languages ``C``, ``CXX``, and ``Fortran`` are supported.
32
33It makes no sense to use this module when :policy:`CMP0069` is set to ``OLD`` so
34module will return error in this case. See policy :policy:`CMP0069` for details.
35
36.. versionadded:: 3.13
37  Add support for Visual Studio generators.
38
39Examples
40^^^^^^^^
41
42.. code-block:: cmake
43
44  check_ipo_supported() # fatal error if IPO is not supported
45  set_property(TARGET foo PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
46
47.. code-block:: cmake
48
49  # Optional IPO. Do not use IPO if it's not supported by compiler.
50  check_ipo_supported(RESULT result OUTPUT output)
51  if(result)
52    set_property(TARGET foo PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
53  else()
54    message(WARNING "IPO is not supported: ${output}")
55  endif()
56
57#]=======================================================================]
58
59# X_RESULT - name of the final result variable
60# X_OUTPUT - name of the variable with information about error
61macro(_ipo_not_supported output)
62  if(NOT X_RESULT)
63    message(FATAL_ERROR "IPO is not supported (${output}).")
64  endif()
65
66  set("${X_RESULT}" NO PARENT_SCOPE)
67  if(X_OUTPUT)
68    set("${X_OUTPUT}" "${output}" PARENT_SCOPE)
69  endif()
70endmacro()
71
72# Run IPO/LTO test
73macro(_ipo_run_language_check language)
74  set(testdir "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/_CMakeLTOTest-${language}")
75
76  file(REMOVE_RECURSE "${testdir}")
77  file(MAKE_DIRECTORY "${testdir}")
78
79  set(bindir "${testdir}/bin")
80  set(srcdir "${testdir}/src")
81
82  file(MAKE_DIRECTORY "${bindir}")
83  file(MAKE_DIRECTORY "${srcdir}")
84
85  set(TRY_COMPILE_PROJECT_NAME "lto-test")
86
87  set(try_compile_src "${CMAKE_ROOT}/Modules/CheckIPOSupported")
88
89  # Use:
90  # * TRY_COMPILE_PROJECT_NAME
91  # * CMAKE_VERSION
92  configure_file(
93      "${try_compile_src}/CMakeLists-${language}.txt.in"
94      "${srcdir}/CMakeLists.txt"
95      @ONLY
96  )
97
98  string(COMPARE EQUAL "${language}" "C" is_c)
99  string(COMPARE EQUAL "${language}" "CXX" is_cxx)
100  string(COMPARE EQUAL "${language}" "Fortran" is_fortran)
101
102  if(is_c)
103    set(copy_sources foo.c main.c)
104  elseif(is_cxx)
105    set(copy_sources foo.cpp main.cpp)
106  elseif(is_fortran)
107    set(copy_sources foo.f main.f)
108  else()
109    message(FATAL_ERROR "Language not supported")
110  endif()
111
112  foreach(x ${copy_sources})
113    configure_file(
114        "${try_compile_src}/${x}"
115        "${srcdir}/${x}"
116        COPYONLY
117    )
118  endforeach()
119
120  try_compile(
121      _IPO_LANGUAGE_CHECK_RESULT
122      "${bindir}"
123      "${srcdir}"
124      "${TRY_COMPILE_PROJECT_NAME}"
125      CMAKE_FLAGS
126      "-DCMAKE_VERBOSE_MAKEFILE=ON"
127      "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON"
128      OUTPUT_VARIABLE output
129  )
130  set(_IPO_LANGUAGE_CHECK_RESULT "${_IPO_LANGUAGE_CHECK_RESULT}")
131  unset(_IPO_LANGUAGE_CHECK_RESULT CACHE)
132
133  if(NOT _IPO_LANGUAGE_CHECK_RESULT)
134    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
135      "${language} compiler IPO check failed with the following output:\n"
136      "${output}\n")
137    _ipo_not_supported("check failed to compile")
138    if(X_OUTPUT)
139      set("${X_OUTPUT}" "${output}" PARENT_SCOPE)
140    endif()
141    return()
142  endif()
143endmacro()
144
145function(check_ipo_supported)
146  cmake_policy(GET CMP0069 x)
147
148  string(COMPARE EQUAL "${x}" "" not_set)
149  if(not_set)
150    message(FATAL_ERROR "Policy CMP0069 is not set")
151  endif()
152
153  string(COMPARE EQUAL "${x}" "OLD" is_old)
154  if(is_old)
155    message(FATAL_ERROR "Policy CMP0069 set to OLD")
156  endif()
157
158  set(optional)
159  set(one RESULT OUTPUT)
160  set(multiple LANGUAGES)
161
162  # Introduce:
163  # * X_RESULT
164  # * X_OUTPUT
165  # * X_LANGUAGES
166  cmake_parse_arguments(X "${optional}" "${one}" "${multiple}" "${ARGV}")
167
168  string(COMPARE NOTEQUAL "${X_UNPARSED_ARGUMENTS}" "" has_unparsed)
169  if(has_unparsed)
170    message(FATAL_ERROR "Unparsed arguments: ${X_UNPARSED_ARGUMENTS}")
171  endif()
172
173  string(COMPARE EQUAL "${X_LANGUAGES}" "" no_languages)
174  if(no_languages)
175    # User did not set any languages, use defaults
176    get_property(enabled_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
177    string(COMPARE EQUAL "${enabled_languages}" "" no_languages)
178    if(no_languages)
179      _ipo_not_supported(
180          "no languages found in ENABLED_LANGUAGES global property"
181      )
182      return()
183    endif()
184
185    set(languages "")
186    list(FIND enabled_languages "CXX" result)
187    if(NOT result EQUAL -1)
188      list(APPEND languages "CXX")
189    endif()
190
191    list(FIND enabled_languages "C" result)
192    if(NOT result EQUAL -1)
193      list(APPEND languages "C")
194    endif()
195
196    list(FIND enabled_languages "Fortran" result)
197    if(NOT result EQUAL -1)
198      list(APPEND languages "Fortran")
199    endif()
200
201    string(COMPARE EQUAL "${languages}" "" no_languages)
202    if(no_languages)
203      _ipo_not_supported(
204          "no C/CXX/Fortran languages found in ENABLED_LANGUAGES global property"
205      )
206      return()
207    endif()
208  else()
209    set(languages "${X_LANGUAGES}")
210
211    set(unsupported_languages "${languages}")
212    list(REMOVE_ITEM unsupported_languages "C" "CXX" "Fortran")
213    string(COMPARE NOTEQUAL "${unsupported_languages}" "" has_unsupported)
214    if(has_unsupported)
215      _ipo_not_supported(
216          "language(s) '${unsupported_languages}' not supported"
217      )
218      return()
219    endif()
220  endif()
221
222  foreach(lang ${languages})
223    if(NOT _CMAKE_${lang}_IPO_SUPPORTED_BY_CMAKE)
224      _ipo_not_supported("CMake doesn't support IPO for current ${lang} compiler")
225      return()
226    endif()
227
228    if(NOT _CMAKE_${lang}_IPO_MAY_BE_SUPPORTED_BY_COMPILER)
229      _ipo_not_supported("${lang} compiler doesn't support IPO")
230      return()
231    endif()
232  endforeach()
233
234  if(CMAKE_GENERATOR MATCHES "^Visual Studio 9 ")
235    _ipo_not_supported("CMake doesn't support IPO for current generator")
236    return()
237  endif()
238
239  foreach(x ${languages})
240    _ipo_run_language_check(${x})
241  endforeach()
242
243  set("${X_RESULT}" YES PARENT_SCOPE)
244endfunction()
245