X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=cmake%2Fmodules%2FHandleLLVMOptions.cmake;h=90d766a4fb6e7889c8a396e084a1738b3141657f;hp=ca07c5c36182eb97521e1a99655019ada5d2e684;hb=1496d41753a3914482e85e0689fc8f38fdc9374d;hpb=d6a93075a1058072e3b2525d26b3516404a7cef4

diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index ca07c5c3618..90d766a4fb6 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -2,27 +2,45 @@
 # options and executing the appropriate CMake commands to realize the users'
 # selections.
 
+include(HandleLLVMStdlib)
 include(AddLLVMDefinitions)
 include(CheckCCompilerFlag)
+include(CheckCXXCompilerFlag)
 
-if( CMAKE_COMPILER_IS_GNUCXX )
-  set(LLVM_COMPILER_IS_GCC_COMPATIBLE ON)
-elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" )
-  set(LLVM_COMPILER_IS_GCC_COMPATIBLE ON)
-endif()
+if(NOT LLVM_FORCE_USE_OLD_TOOLCHAIN)
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.7)
+      message(FATAL_ERROR "Host GCC version must be at least 4.7!")
+    endif()
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.1)
+      message(FATAL_ERROR "Host Clang version must be at least 3.1!")
+    endif()
 
-# Run-time build mode; It is used for unittests.
-if(MSVC_IDE)
-  # Expect "$(Configuration)", "$(OutDir)", etc.
-  # It is expanded by msbuild or similar.
-  set(RUNTIME_BUILD_MODE "${CMAKE_CFG_INTDIR}")
-elseif(NOT CMAKE_BUILD_TYPE STREQUAL "")
-  # Expect "Release" "Debug", etc.
-  # Or unittests could not run.
-  set(RUNTIME_BUILD_MODE ${CMAKE_BUILD_TYPE})
-else()
-  # It might be "."
-  set(RUNTIME_BUILD_MODE "${CMAKE_CFG_INTDIR}")
+    # Also test that we aren't using too old of a version of libstdc++ with the
+    # Clang compiler. This is tricky as there is no real way to check the
+    # version of libstdc++ directly. Instead we test for a known bug in
+    # libstdc++4.6 that is fixed in libstdc++4.7.
+    if(NOT LLVM_ENABLE_LIBCXX)
+      set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+      set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
+      set(CMAKE_REQUIRED_FLAGS "-std=c++0x")
+      check_cxx_source_compiles("
+#include <atomic>
+std::atomic<float> x(0.0f);
+int main() { return (float)x; }"
+        LLVM_NO_OLD_LIBSTDCXX)
+      if(NOT LLVM_NO_OLD_LIBSTDCXX)
+        message(FATAL_ERROR "Host Clang must be able to find libstdc++4.7 or newer!")
+      endif()
+      set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+      set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES})
+    endif()
+  elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 17.0)
+      message(FATAL_ERROR "Host Visual Studio must be at least 2012 (MSVC 17.0)")
+    endif()
+  endif()
 endif()
 
 if( LLVM_ENABLE_ASSERTIONS )
@@ -30,20 +48,26 @@ if( LLVM_ENABLE_ASSERTIONS )
   if( NOT MSVC )
     add_definitions( -D_DEBUG )
   endif()
-  # On Release builds cmake automatically defines NDEBUG, so we
+  # On non-Debug builds cmake automatically defines NDEBUG, so we
   # explicitly undefine it:
-  if( uppercase_CMAKE_BUILD_TYPE STREQUAL "RELEASE" )
+  if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
     add_definitions( -UNDEBUG )
-  endif()
-else()
-  if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "RELEASE" )
-    if( NOT MSVC_IDE AND NOT XCODE )
-      add_definitions( -DNDEBUG )
-    endif()
+    # Also remove /D NDEBUG to avoid MSVC warnings about conflicting defines.
+    foreach (flags_var_to_scrub
+        CMAKE_CXX_FLAGS_RELEASE
+        CMAKE_CXX_FLAGS_RELWITHDEBINFO
+        CMAKE_CXX_FLAGS_MINSIZEREL
+        CMAKE_C_FLAGS_RELEASE
+        CMAKE_C_FLAGS_RELWITHDEBINFO
+        CMAKE_C_FLAGS_MINSIZEREL)
+      string (REGEX REPLACE "(^| )[/-]D *NDEBUG($| )" " "
+        "${flags_var_to_scrub}" "${${flags_var_to_scrub}}")
+    endforeach()
   endif()
 endif()
 
 if(WIN32)
+  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
   if(CYGWIN)
     set(LLVM_ON_WIN32 0)
     set(LLVM_ON_UNIX 1)
@@ -51,8 +75,6 @@ if(WIN32)
     set(LLVM_ON_WIN32 1)
     set(LLVM_ON_UNIX 0)
   endif(CYGWIN)
-  set(LTDL_SHLIB_EXT ".dll")
-  set(EXEEXT ".exe")
   # Maximum path length is 160 for non-unicode paths
   set(MAXPATHLEN 160)
 else(WIN32)
@@ -60,11 +82,10 @@ else(WIN32)
     set(LLVM_ON_WIN32 0)
     set(LLVM_ON_UNIX 1)
     if(APPLE)
-      set(LTDL_SHLIB_EXT ".dylib")
+      set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
     else(APPLE)
-      set(LTDL_SHLIB_EXT ".so")
+      set(LLVM_HAVE_LINK_VERSION_SCRIPT 1)
     endif(APPLE)
-    set(EXEEXT "")
     # FIXME: Maximum path length is currently set to 'safe' fixed value
     set(MAXPATHLEN 2024)
   else(UNIX)
@@ -72,6 +93,50 @@ else(WIN32)
   endif(UNIX)
 endif(WIN32)
 
+set(EXEEXT ${CMAKE_EXECUTABLE_SUFFIX})
+set(LTDL_SHLIB_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
+
+# We use *.dylib rather than *.so on darwin.
+set(LLVM_PLUGIN_EXT ${CMAKE_SHARED_LIBRARY_SUFFIX})
+
+if(APPLE)
+  # Darwin-specific linker flags for loadable modules.
+  set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
+endif()
+
+function(append value)
+  foreach(variable ${ARGN})
+    set(${variable} "${${variable}} ${value}" PARENT_SCOPE)
+  endforeach(variable)
+endfunction()
+
+function(append_if condition value)
+  if (${condition})
+    foreach(variable ${ARGN})
+      set(${variable} "${${variable}} ${value}" PARENT_SCOPE)
+    endforeach(variable)
+  endif()
+endfunction()
+
+macro(add_flag_if_supported flag name)
+  check_c_compiler_flag("-Werror ${flag}" "C_SUPPORTS_${name}")
+  append_if("C_SUPPORTS_${name}" "${flag}" CMAKE_C_FLAGS)
+  check_cxx_compiler_flag("-Werror ${flag}" "CXX_SUPPORTS_${name}")
+  append_if("CXX_SUPPORTS_${name}" "${flag}" CMAKE_CXX_FLAGS)
+endmacro()
+
+function(add_flag_or_print_warning flag name)
+  check_c_compiler_flag("-Werror ${flag}" "C_SUPPORTS_${name}")
+  check_cxx_compiler_flag("-Werror ${flag}" "CXX_SUPPORTS_${name}")
+  if (C_SUPPORTS_${name} AND CXX_SUPPORTS_${name})
+    message(STATUS "Building with ${flag}")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}" PARENT_SCOPE)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${flag}" PARENT_SCOPE)
+  else()
+    message(WARNING "${flag} is not supported.")
+  endif()
+endfunction()
+
 if( LLVM_ENABLE_PIC )
   if( XCODE )
     # Xcode has -mdynamic-no-pic on by default, which overrides -fPIC. I don't
@@ -80,24 +145,14 @@ if( LLVM_ENABLE_PIC )
   elseif( WIN32 OR CYGWIN)
     # On Windows all code is PIC. MinGW warns if -fPIC is used.
   else()
-    include(CheckCXXCompilerFlag)
-    check_cxx_compiler_flag("-fPIC" SUPPORTS_FPIC_FLAG)
-    if( SUPPORTS_FPIC_FLAG )
-      message(STATUS "Building with -fPIC")
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
-      set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")
-    else( SUPPORTS_FPIC_FLAG )
-      message(WARNING "-fPIC not supported.")
-    endif()
+    add_flag_or_print_warning("-fPIC" FPIC)
 
     if( WIN32 OR CYGWIN)
       # MinGW warns if -fvisibility-inlines-hidden is used.
     else()
       check_cxx_compiler_flag("-fvisibility-inlines-hidden" SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG)
-      if( SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG )
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility-inlines-hidden")
-      endif()
-     endif()
+      append_if(SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG "-fvisibility-inlines-hidden" CMAKE_CXX_FLAGS)
+    endif()
   endif()
 endif()
 
@@ -112,6 +167,29 @@ if( CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT WIN32 )
   endif( LLVM_BUILD_32_BITS )
 endif( CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT WIN32 )
 
+if( XCODE )
+  # For Xcode enable several build settings that correspond to
+  # many warnings that are on by default in Clang but are
+  # not enabled for historical reasons.  For versions of Xcode
+  # that do not support these options they will simply
+  # be ignored.
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_ABOUT_RETURN_TYPE "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_ABOUT_MISSING_NEWLINE "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_UNUSED_VALUE "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_UNUSED_VARIABLE "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_SIGN_COMPARE "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_UNUSED_FUNCTION "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_HIDDEN_VIRTUAL_FUNCTIONS "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_UNINITIALIZED_AUTOS "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_BOOL_CONVERSION "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_EMPTY_BODY "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_ENUM_CONVERSION "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_INT_CONVERSION "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_CLANG_WARN_CONSTANT_CONVERSION "YES")
+  set(CMAKE_XCODE_ATTRIBUTE_GCC_WARN_NON_VIRTUAL_DESTRUCTOR "YES")
+endif()
+
 # On Win32 using MS tools, provide an option to set the number of parallel jobs
 # to use.
 if( MSVC_IDE )
@@ -121,14 +199,8 @@ if( MSVC_IDE )
     if( LLVM_COMPILER_JOBS STREQUAL "0" )
       add_llvm_definitions( /MP )
     else()
-      if (MSVC10)
-        message(FATAL_ERROR
-          "Due to a bug in CMake only 0 and 1 is supported for "
-          "LLVM_COMPILER_JOBS when generating for Visual Studio 2010")
-      else()
-        message(STATUS "Number of parallel compiler jobs set to " ${LLVM_COMPILER_JOBS})
-        add_llvm_definitions( /MP${LLVM_COMPILER_JOBS} )
-      endif()
+      message(STATUS "Number of parallel compiler jobs set to " ${LLVM_COMPILER_JOBS})
+      add_llvm_definitions( /MP${LLVM_COMPILER_JOBS} )
     endif()
   else()
     message(STATUS "Parallel compilation disabled")
@@ -138,10 +210,19 @@ endif()
 if( MSVC )
   include(ChooseMSVCCRT)
 
+  if( NOT (${CMAKE_VERSION} VERSION_LESS 2.8.11) )
+    # set stack reserved size to ~10MB
+    # CMake previously automatically set this value for MSVC builds, but the
+    # behavior was changed in CMake 2.8.11 (Issue 12437) to use the MSVC default
+    # value (1 MB) which is not enough for us in tasks such as parsing recursive
+    # C++ templates in Clang.
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /STACK:10000000")
+  endif()
+
   if( MSVC11 )
     add_llvm_definitions(-D_VARIADIC_MAX=10)
   endif()
-
+  
   # Add definitions that make MSVC much less annoying.
   add_llvm_definitions(
     # For some reason MS wants to deprecate a bunch of standard functions...
@@ -153,30 +234,25 @@ if( MSVC )
     -D_SCL_SECURE_NO_WARNINGS
 
     # Disabled warnings.
-    -wd4065 # Suppress 'switch statement contains 'default' but no 'case' labels'
     -wd4146 # Suppress 'unary minus operator applied to unsigned type, result still unsigned'
     -wd4180 # Suppress 'qualifier applied to function type has no meaning; ignored'
-    -wd4181 # Suppress 'qualifier applied to reference type; ignored'
-    -wd4224 # Suppress 'nonstandard extension used : formal parameter 'identifier' was previously defined as a type'
     -wd4244 # Suppress ''argument' : conversion from 'type1' to 'type2', possible loss of data'
+    -wd4258 # Suppress ''var' : definition from the for loop is ignored; the definition from the enclosing scope is used'
     -wd4267 # Suppress ''var' : conversion from 'size_t' to 'type', possible loss of data'
-    -wd4275 # Suppress 'An exported class was derived from a class that was not exported.'
     -wd4291 # Suppress ''declaration' : no matching operator delete found; memory will not be freed if initialization throws an exception'
     -wd4345 # Suppress 'behavior change: an object of POD type constructed with an initializer of the form () will be default-initialized'
     -wd4351 # Suppress 'new behavior: elements of array 'array' will be default initialized'
     -wd4355 # Suppress ''this' : used in base member initializer list'
     -wd4503 # Suppress ''identifier' : decorated name length exceeded, name was truncated'
-    -wd4551 # Suppress 'function call missing argument list'
     -wd4624 # Suppress ''derived class' : destructor could not be generated because a base class destructor is inaccessible'
-    -wd4715 # Suppress ''function' : not all control paths return a value'
+    -wd4722 # Suppress 'function' : destructor never returns, potential memory leak
     -wd4800 # Suppress ''type' : forcing value to bool 'true' or 'false' (performance warning)'
-
+    
     # Promoted warnings.
     -w14062 # Promote 'enumerator in switch of enum is not handled' to level 1 warning.
 
     # Promoted warnings to errors.
     -we4238 # Promote 'nonstandard extension used : class rvalue used as lvalue' to error.
-    -we4239 # Promote 'nonstandard extension used : 'token' : conversion from 'type' to 'type'' to error.
     )
 
   # Enable warnings
@@ -191,24 +267,195 @@ if( MSVC )
   endif (LLVM_ENABLE_WERROR)
 elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
   if (LLVM_ENABLE_WARNINGS)
-    add_llvm_definitions( -Wall -W -Wno-unused-parameter -Wwrite-strings )
-    if (LLVM_ENABLE_PEDANTIC)
-      add_llvm_definitions( -pedantic -Wno-long-long )
-    endif (LLVM_ENABLE_PEDANTIC)
-    check_cxx_compiler_flag("-Werror -Wcovered-switch-default" CXX_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG)
-    if( CXX_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG )
-      set( CMAKE_CXX_FlAGS "${CMAKE_CXX_FLAGS} -Wcovered-switch-default" )
+    append("-Wall -W -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+
+    # Turn off missing field initializer warnings for gcc to avoid noise from
+    # false positives with empty {}. Turn them on otherwise (they're off by
+    # default for clang).
+    check_cxx_compiler_flag("-Wmissing-field-initializers" CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG)
+    if (CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG)
+      if (CMAKE_COMPILER_IS_GNUCXX)
+        append("-Wno-missing-field-initializers" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      else()
+        append("-Wmissing-field-initializers" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      endif()
     endif()
-    check_c_compiler_flag("-Werror -Wcovered-switch-default" C_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG)
-    if( C_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG )
-      set( CMAKE_C_FlAGS "${CMAKE_C_FLAGS} -Wcovered-switch-default" )
+
+    append_if(LLVM_ENABLE_PEDANTIC "-pedantic -Wno-long-long" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+    add_flag_if_supported("-Wcovered-switch-default" COVERED_SWITCH_DEFAULT_FLAG)
+    append_if(USE_NO_UNINITIALIZED "-Wno-uninitialized" CMAKE_CXX_FLAGS)
+    append_if(USE_NO_MAYBE_UNINITIALIZED "-Wno-maybe-uninitialized" CMAKE_CXX_FLAGS)
+
+    # Check if -Wnon-virtual-dtor warns even though the class is marked final.
+    # If it does, don't add it. So it won't be added on clang 3.4 and older.
+    # This also catches cases when -Wnon-virtual-dtor isn't supported by
+    # the compiler at all.
+    set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11 -Werror=non-virtual-dtor")
+    CHECK_CXX_SOURCE_COMPILES("class base {public: virtual void anchor();protected: ~base();};
+                               class derived final : public base { public: ~derived();};
+                               int main() { return 0; }"
+                              CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR)
+    set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+    append_if(CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR
+              "-Wnon-virtual-dtor" CMAKE_CXX_FLAGS)
+
+    # Check if -Wcomment is OK with an // comment ending with '\' if the next
+    # line is also a // comment.
+    set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror -Wcomment")
+    CHECK_C_SOURCE_COMPILES("// \\\\\\n//\\nint main() {return 0;}"
+                            C_WCOMMENT_ALLOWS_LINE_WRAP)
+    set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+    if (NOT C_WCOMMENT_ALLOWS_LINE_WRAP)
+      append("-Wno-comment" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     endif()
   endif (LLVM_ENABLE_WARNINGS)
-  if (LLVM_ENABLE_WERROR)
-    add_llvm_definitions( -Werror )
-  endif (LLVM_ENABLE_WERROR)
+  append_if(LLVM_ENABLE_WERROR "-Werror" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  if (NOT LLVM_ENABLE_TIMESTAMPS)
+    add_flag_if_supported("-Werror=date-time" WERROR_DATE_TIME)
+  endif ()
+  if (LLVM_ENABLE_CXX1Y)
+    check_cxx_compiler_flag("-std=c++1y" CXX_SUPPORTS_CXX1Y)
+    append_if(CXX_SUPPORTS_CXX1Y "-std=c++1y" CMAKE_CXX_FLAGS)
+  else()
+    check_cxx_compiler_flag("-std=c++11" CXX_SUPPORTS_CXX11)
+    if (CXX_SUPPORTS_CXX11)
+      if (CYGWIN OR MINGW)
+        # MinGW and Cygwin are a bit stricter and lack things like
+        # 'strdup', 'stricmp', etc in c++11 mode.
+        append("-std=gnu++11" CMAKE_CXX_FLAGS)
+      else()
+        append("-std=c++11" CMAKE_CXX_FLAGS)
+      endif()
+    else()
+      message(FATAL_ERROR "LLVM requires C++11 support but the '-std=c++11' flag isn't supported.")
+    endif()
+  endif()
+  if (LLVM_ENABLE_MODULES)
+    set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fmodules -fcxx-modules")
+    # Check that we can build code with modules enabled, and that repeatedly
+    # including <cassert> still manages to respect NDEBUG properly.
+    CHECK_CXX_SOURCE_COMPILES("#undef NDEBUG
+                               #include <cassert>
+                               #define NDEBUG
+                               #include <cassert>
+                               int main() { assert(this code is not compiled); }"
+                               CXX_SUPPORTS_MODULES)
+    set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+    if (CXX_SUPPORTS_MODULES)
+      append_if(CXX_SUPPORTS_MODULES "-fmodules" CMAKE_C_FLAGS)
+      append_if(CXX_SUPPORTS_MODULES "-fmodules -fcxx-modules" CMAKE_CXX_FLAGS)
+    else()
+      message(FATAL_ERROR "LLVM_ENABLE_MODULES is not supported by this compiler")
+    endif()
+  endif(LLVM_ENABLE_MODULES)
 endif( MSVC )
 
+macro(append_common_sanitizer_flags)
+  # Append -fno-omit-frame-pointer and turn on debug info to get better
+  # stack traces.
+  add_flag_if_supported("-fno-omit-frame-pointer" FNO_OMIT_FRAME_POINTER)
+  if (NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" AND
+      NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "RELWITHDEBINFO")
+    add_flag_if_supported("-gline-tables-only" GLINE_TABLES_ONLY)
+  endif()
+  # Use -O1 even in debug mode, otherwise sanitizers slowdown is too large.
+  if (uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+    add_flag_if_supported("-O1" O1)
+  endif()
+endmacro()
+
+# Turn on sanitizers if necessary.
+if(LLVM_USE_SANITIZER)
+  if (LLVM_ON_UNIX)
+    if (LLVM_USE_SANITIZER STREQUAL "Address")
+      append_common_sanitizer_flags()
+      append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+    elseif (LLVM_USE_SANITIZER MATCHES "Memory(WithOrigins)?")
+      append_common_sanitizer_flags()
+      append("-fsanitize=memory" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      if(LLVM_USE_SANITIZER STREQUAL "MemoryWithOrigins")
+        append("-fsanitize-memory-track-origins" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      endif()
+    elseif (LLVM_USE_SANITIZER STREQUAL "Undefined")
+      append_common_sanitizer_flags()
+      append("-fsanitize=undefined -fno-sanitize=vptr,function -fno-sanitize-recover"
+              CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+    else()
+      message(WARNING "Unsupported value of LLVM_USE_SANITIZER: ${LLVM_USE_SANITIZER}")
+    endif()
+  else()
+    message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
+  endif()
+endif()
+
+# Turn on -gsplit-dwarf if requested
+if(LLVM_USE_SPLIT_DWARF)
+  add_definitions("-gsplit-dwarf")
+endif()
+
 add_llvm_definitions( -D__STDC_CONSTANT_MACROS )
 add_llvm_definitions( -D__STDC_FORMAT_MACROS )
 add_llvm_definitions( -D__STDC_LIMIT_MACROS )
+
+# clang doesn't print colored diagnostics when invoked from Ninja
+if (UNIX AND
+    CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND
+    CMAKE_GENERATOR STREQUAL "Ninja")
+  append("-fcolor-diagnostics" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+endif()
+
+# Add flags for add_dead_strip().
+# FIXME: With MSVS, consider compiling with /Gy and linking with /OPT:REF?
+# But MinSizeRel seems to add that automatically, so maybe disable these
+# flags instead if LLVM_NO_DEAD_STRIP is set.
+if(NOT CYGWIN AND NOT WIN32)
+  if(NOT ${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+    check_c_compiler_flag("-Werror -fno-function-sections" C_SUPPORTS_FNO_FUNCTION_SECTIONS)
+    if (C_SUPPORTS_FNO_FUNCTION_SECTIONS)
+      # Don't add -ffunction-section if it can be disabled with -fno-function-sections.
+      # Doing so will break sanitizers.
+      add_flag_if_supported("-ffunction-sections" FFUNCTION_SECTIONS)
+    endif()
+    add_flag_if_supported("-fdata-sections" FDATA_SECTIONS)
+  endif()
+endif()
+
+if(CYGWIN OR MINGW)
+  # Prune --out-implib from executables. It doesn't make sense even
+  # with --export-all-symbols.
+  string(REGEX REPLACE "-Wl,--out-implib,[^ ]+ " " "
+    CMAKE_C_LINK_EXECUTABLE "${CMAKE_C_LINK_EXECUTABLE}")
+  string(REGEX REPLACE "-Wl,--out-implib,[^ ]+ " " "
+    CMAKE_CXX_LINK_EXECUTABLE "${CMAKE_CXX_LINK_EXECUTABLE}")
+endif()
+
+if(MSVC)
+  # Remove flags here, for exceptions and RTTI.
+  # Each target property or source property should be responsible to control
+  # them.
+  # CL.EXE complains to override flags like "/GR /GR-".
+  string(REGEX REPLACE "(^| ) */EH[-cs]+ *( |$)" "\\1 \\2" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  string(REGEX REPLACE "(^| ) */GR-? *( |$)" "\\1 \\2" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+endif()
+
+# Provide public options to globally control RTTI and EH
+option(LLVM_ENABLE_EH "Enable Exception handling" OFF)
+option(LLVM_ENABLE_RTTI "Enable run time type information" OFF)
+if(LLVM_ENABLE_EH AND NOT LLVM_ENABLE_RTTI)
+  message(FATAL_ERROR "Exception handling requires RTTI. You must set LLVM_ENABLE_RTTI to ON")
+endif()
+
+# Plugin support
+# FIXME: Make this configurable.
+if(WIN32 OR CYGWIN)
+  if(BUILD_SHARED_LIBS)
+    set(LLVM_ENABLE_PLUGINS ON)
+  else()
+    set(LLVM_ENABLE_PLUGINS OFF)
+  endif()
+else()
+  set(LLVM_ENABLE_PLUGINS ON)
+endif()