Use C99 to compile ISL

ISL with small integer optimization requires C99 to compile. gcc < 5.0
still uses C89 as default, so we need to enable the options to compile
in C99 mode.

This patch is preparing the actual activation of small integer
optimization.

Differential version: http://reviews.llvm.org/D10610

Reviewers: grosser
llvm-svn: 240322

polly/Makefile.config.in

@@ -39,8 +39,13 @@ POLLY_CXXFLAGS += "-fno-rtti -fno-exceptions"
 #
 # We also disable all warnings, as these should be fixed upstream. There is
 # no value in reporting them here.
+#
+# ISL with activated small integer optimization use C99 extern inline
+# semantics. In order to work, we need to enable C99 mode (instead the default
+# -std=gnu89 in case of gcc)
 POLLY_CFLAGS := -fvisibility=hidden
 POLLY_CFLAGS += -w
+POLLY_CFLAGS += -std=gnu99
 
 CUDALIB_FOUND := @cuda_found@
 

polly/cmake/polly_macros.cmake

@@ -71,3 +71,13 @@ macro(add_polly_loadable_module name)
       LINK_FLAGS "-Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
   endif()
 endmacro(add_polly_loadable_module)
+
+# # Use C99-compatible compile mode for all C source files of a target.
+function(target_enable_c99 _target)
+  if(CMAKE_VERSION VERSION_GREATER "3.1")
+    set_target_properties("${_target}" PROPERTIES C_STANDARD 99)
+  elseif(CMAKE_COMPILER_IS_GNUCC)
+    get_target_property(_sources "${_target}" SOURCES)
+    set_source_files_properties(${_sources} COMPILE_FLAGS "-std=gnu99")
+  endif()
+endfunction()

polly/lib/CMakeLists.txt

@@ -189,6 +189,9 @@ add_polly_library(Polly
   ${ISL_FILES}
   )
 
+# ISL requires at least C99 to compile. gcc < 5.0 use -std=gnu89 as default.
+target_enable_c99(Polly)
+
 if (BUILD_SHARED_LIBS)
   target_link_libraries(Polly
     LLVMSupport