[Polly] Use C99 to compile ISL

[Meinersbur]

Summary

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.

The actual activation of small integer optimization will follow after this commit.

[grosser]

LGTM

[Meinersbur]

Committed as r240322

Makefile.config.in

 # the CFLAGS to identify them.
 #
 # We first set the visibility of all isl functions to hidden to ensure we do
 # not clash with other isl versions that got linked into a program that uses
 # Polly. (This happens e.g when linking Polly with dragonegg)
 #
 # 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@
 
 # Set include directories
 POLLY_INC :=  @cuda_inc@ \
               -I$(POLLY_OBJ_ROOT)/lib/External/isl \
               -I$(POLLY_SRC_ROOT)/lib/JSON/include \
               -I$(POLLY_SRC_ROOT)/lib/External/isl/include \
               -I$(POLLY_SRC_ROOT)/lib/External/isl/imath \
               -I$(POLLY_SRC_ROOT)/lib/External/isl
 
 POLLY_LD := @cuda_ld@
 
 POLLY_LIB := @cuda_lib@

cmake/polly_macros.cmake

if (GLOBAL_NOT_MODULE)
     unset (MODULE)
   endif()
   if (APPLE)
     # Darwin-specific linker flags for loadable modules.
     set_target_properties(${name} PROPERTIES
       LINK_FLAGS "-Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
   endif()
 endmacro(add_polly_loadable_module)
+
+# # Use C99-compatible compile mode for all C source files of a target.
+function(target_enable_c99 _target)
+  if(CMAKE_VERSION VERSION_GREATER "3.1")
+    set_target_properties("${_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()

lib/CMakeLists.txt

add_polly_library(Polly
   Transform/Canonicalization.cpp
   Transform/CodePreparation.cpp
   Transform/DeadCodeElimination.cpp
   Transform/IndependentBlocks.cpp
   Transform/ScheduleOptimizer.cpp
   ${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
     LLVMCore
     LLVMScalarOpts
     LLVMInstCombine
     LLVMTransformUtils
     LLVMAnalysis