CPU: Add CMake glue to populate header search paths

Also disable PCH in preparation of merge

src/ngraph/CMakeLists.txt

@@ -101,7 +101,8 @@ include_directories(
 if(LLVM_INCLUDE_DIR)
     include_directories(SYSTEM ${LLVM_INCLUDE_DIR})
     link_directories(${LLVM_LIB_DIR})
-    # Add sources for the LLVM-based code generator
+    # Add sources for the CPU backend
+    # and all its dependencies
     set(SRC ${SRC}
         codegen/compiler.cpp
         runtime/cpu/call_frame.cpp
@@ -110,7 +111,10 @@ if(LLVM_INCLUDE_DIR)
         runtime/cpu/emitter.cpp
         runtime/cpu/external_function.cpp
         )
+    # LLVM binary builds are typically built without RTTI
     set_source_files_properties(codegen/compiler.cpp PROPERTIES COMPILE_FLAGS "-fno-rtti")
+    set_source_files_properties(codegen/compiler.cpp PROPERTIES COMPILE_DEFINITIONS
+      "EIGEN_HEADERS_PATH=\"${EIGEN_INCLUDE_DIR}\";CLANG_BUILTIN_HEADERS_PATH=\"${LLVM_LIB_DIR}/clang/5.0.0/include\";NGRAPH_HEADERS_PATH=\"${NGRAPH_INCLUDE_PATH}\"")
 endif()
 
 add_library(ngraph SHARED ${SRC})

src/ngraph/codegen/compiler.cpp

@@ -123,7 +123,7 @@ std::unique_ptr<llvm::Module> execution_state::compile(const string& source, con
     // But that's a private header and isn't part of the public libclang API
     // Instead of re-implementing all of that functionality in a custom toolchain
     // just hardcode the paths relevant to frequently used build/test machines for now
-    HSO.AddPath("/localdisk/menonjai/build/third-party/ext_llvm-prefix/src/ext_llvm/lib/clang/5.0.0/include", clang::frontend::System, false, false);
+    HSO.AddPath(CLANG_BUILTIN_HEADERS_PATH, clang::frontend::System, false, false);
     HSO.AddPath("/usr/include/x86_64-linux-gnu", clang::frontend::System, false, false);
     HSO.AddPath("/usr/include", clang::frontend::System, false, false);
     // Add C++ standard library headers
@@ -133,12 +133,8 @@ std::unique_ptr<llvm::Module> execution_state::compile(const string& source, con
     // Debian-like + GCC 5 libstdc++
     HSO.AddPath("/usr/include/x86_64-linux-gnu/c++/5", clang::frontend::System, false, false);
     HSO.AddPath("/usr/include/c++/5", clang::frontend::System, false, false);
-    // TODO: Hack in path to eigen headers for now
-    HSO.AddPath("/localdisk/menonjai/build/external/eigen/include/eigen3",
-                clang::frontend::System,
-                false,
-                false);
-    HSO.AddPath("/home/menonjai/ngraph-cpp/src", clang::frontend::System, false, false);
+    HSO.AddPath(EIGEN_HEADERS_PATH, clang::frontend::System, false, false);
+    HSO.AddPath(NGRAPH_HEADERS_PATH, clang::frontend::System, false, false);
 
     // Language options
     auto LO = Clang->getInvocation().getLangOpts();

src/ngraph/runtime/cpu/external_function.cpp

@@ -61,7 +61,7 @@
 
 // TODO: Decide if we want to ship this or
 // just enable it for developer build-test cycles
-#define NGCPU_PCH
+//#define NGCPU_PCH
 
 using namespace std;
 using namespace ngraph::runtime::cpu;