[Build] Resolved All IPO Warnings in VTR

After discussing with other developers on VTR, decided to globally
suppress all known IPO warnings in VTR.

Author: AlexandreSinger

CMakeLists.txt

@@ -227,18 +227,17 @@ foreach(flag ${FLEX_BISON_WARN_SUPPRESS_FLAGS_TO_CHECK})
     endif()
 endforeach()
 
-#Suppress IPO link warnings
-set(IPO_LINK_WARN_SUPRESS_FLAGS " ")
-set(IPO_LINK_WARN_SUPRESS_FLAGS_TO_CHECK
-    "-Wno-null-dereference"
-    )
-foreach(flag ${IPO_LINK_WARN_SUPRESS_FLAGS_TO_CHECK})
-    CHECK_CXX_COMPILER_FLAG(${flag} CXX_COMPILER_SUPPORTS_${flag})
-    if(CXX_COMPILER_SUPPORTS_${flag})
-        #Flag supported, so enable it
-        set(IPO_LINK_WARN_SUPRESS_FLAGS "${IPO_LINK_WARN_SUPRESS_FLAGS} ${flag}")
-    endif()
-endforeach()
+# Suppress IPO link warnings.
+# When IPO is turned on, it sometimes leads to false positives for warnings
+# since it checks for warnings after some of the source files have been compiled.
+# We globally suppress these warnings here. Any CMake executable which is added
+# after this line.
+if (CMAKE_INTERPROCEDURAL_OPTIMIZATION)
+    message(STATUS "IPO: Suppressing known VTR warnings.")
+    add_link_options(-Wno-alloc-size-larger-than  # libarchfpga allocates C-style arrays using integers.
+                     -Wno-stringop-overflow       # EXTERNAL/capnproto has some string overflow warnings.
+                     )
+endif()
 
 #
 # Sanitizer flags

blifexplorer/CMakeLists.txt

@@ -56,13 +56,6 @@ else()
                             ${CMAKE_DL_LIBS}
     )
 
-    #Supress IPO link warnings if IPO is enabled
-    get_target_property(TEST_BLIFEXPLORER_USES_IPO blifexplorer INTERPROCEDURAL_OPTIMIZATION)
-    if (TEST_BLIFEXPLORER_USES_IPO)
-        set_property(TARGET blifexplorer APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-    endif()
-
-
     install(TARGETS blifexplorer DESTINATION bin)
 
 endif()

libs/libarchfpga/CMakeLists.txt

@@ -53,28 +53,10 @@ endif()
 
 target_compile_definitions(libarchfpga PUBLIC ${INTERCHANGE_SCHEMA_HEADERS})
 
-# Supress IPO link warnings if IPO is enabled
-get_target_property(LIBARCHFPGA_USES_IPO libarchfpga INTERPROCEDURAL_OPTIMIZATION)
-if(LIBARCHFPGA_USES_IPO)
-    # LibArchFPGA uses ints in many of its data structures instead of size_t for
-    # the size of arrays which are used to allocate arrays. At link-time, this
-    # causes many false allocation warnings when IPO is enabled.
-    # In order to suppress these warnings, we must make this PUBLIC so that not
-    # only we suppress the warning for libarchfpga, but also anything else that
-    # links with it.
-    target_link_options(libarchfpga PUBLIC -Wno-alloc-size-larger-than)
-endif()
-
 #Create the test executable
 add_executable(read_arch ${READ_ARCH_EXEC_SRC})
 target_link_libraries(read_arch libarchfpga)
 
-#Supress IPO link warnings if IPO is enabled
-get_target_property(READ_ARCH_USES_IPO read_arch INTERPROCEDURAL_OPTIMIZATION)
-if(READ_ARCH_USES_IPO)
-    set_property(TARGET read_arch APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
 install(TARGETS libarchfpga DESTINATION bin)
 install(FILES ${LIB_HEADERS} DESTINATION include/libarchfpga)
 

odin_ii/CMakeLists.txt

@@ -184,11 +184,5 @@ foreach(ODIN_LINK_FLAG ${ODIN_EXTRA_LINK_FLAGS})
         target_link_libraries(odin_ii ${ODIN_LINK_FLAG})
 endforeach()
 
-#Supress IPO link warnings if IPO is enabled
-get_target_property(ODIN_USES_IPO odin_ii INTERPROCEDURAL_OPTIMIZATION)
-if (ODIN_USES_IPO)
-    set_property(TARGET odin_ii APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
 install(TARGETS odin_ii libodin_ii DESTINATION bin)
 install(FILES ${LIB_HEADERS} DESTINATION include/libodin_ii)

utils/fasm/CMakeLists.txt

@@ -27,12 +27,6 @@ target_link_libraries(fasm
 add_executable(genfasm src/main.cpp)
 target_link_libraries(genfasm fasm)
 
-#Supress IPO link warnings if IPO is enabled
-get_target_property(GENFASM_USES_IPO genfasm INTERPROCEDURAL_OPTIMIZATION)
-if (GENFASM_USES_IPO)
-    set_property(TARGET genfasm APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
 #Specify link-time dependencies
 install(TARGETS genfasm DESTINATION bin)
 
@@ -49,12 +43,6 @@ set(TEST_SOURCES
 add_executable(test_fasm ${TEST_SOURCES})
 target_link_libraries(test_fasm fasm Catch2::Catch2WithMain)
 
-#Suppress IPO link warnings if IPO is enabled
-get_target_property(TEST_FASM_USES_IPO test_fasm INTERPROCEDURAL_OPTIMIZATION)
-if (TEST_FASM_USES_IPO)
-    set_property(TARGET test_fasm APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
 add_test(
   NAME test_fasm
   COMMAND test_fasm --colour-mode ansi

utils/route_diag/CMakeLists.txt

@@ -8,9 +8,3 @@ target_link_libraries(route_diag
   libvpr
   )
 
-#Suppress IPO link warnings if IPO is enabled
-get_target_property(TEST_ROUTE_DIAG_USES_IPO route_diag INTERPROCEDURAL_OPTIMIZATION)
-if (TEST_ROUTE_DIAG_USES_IPO)
-    set_property(TARGET route_diag APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-

vpr/CMakeLists.txt

@@ -175,14 +175,6 @@ add_executable(vpr ${EXEC_SOURCES})
 target_link_libraries(vpr libvpr)
 
 
-#Suppress IPO link warnings if IPO is enabled
-get_target_property(VPR_USES_IPO vpr INTERPROCEDURAL_OPTIMIZATION)
-if (VPR_USES_IPO)
-    set_property(TARGET vpr APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
-
-
 #
 # Profile Guilded Optimization Configuration
 #
@@ -303,12 +295,6 @@ target_link_libraries(test_vpr
                         Catch2::Catch2WithMain
                         libvpr)
 
-#Suppress IPO link warnings if IPO is enabled
-get_target_property(TEST_VPR_USES_IPO vpr INTERPROCEDURAL_OPTIMIZATION)
-if (TEST_VPR_USES_IPO)
-    set_property(TARGET test_vpr APPEND PROPERTY LINK_FLAGS ${IPO_LINK_WARN_SUPRESS_FLAGS})
-endif()
-
 add_test(NAME test_vpr
     COMMAND test_vpr --colour-mode ansi
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/test