Provide a mechanism to shut down global SIMD support (#1627)

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

CMakeLists.txt

@@ -22,6 +22,11 @@ option(SOURCEMETA_CORE_CONTRIB_GOOGLEBENCHMARK "Build the GoogleBenchmark librar
 
 include(Sourcemeta)
 
+# Don't force downstream consumers on it
+if(PROJECT_IS_TOP_LEVEL)
+  sourcemeta_enable_simd()
+endif()
+
 # TODO: Turn this into a re-usable utility CMake function
 if(SOURCEMETA_CORE_INSTALL)
   include(GNUInstallDirs)

cmake/Sourcemeta.cmake

@@ -2,6 +2,7 @@ set(SOURCEMETA_UTILITIES_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}/common")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/shim.cmake")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/variables.cmake")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/defaults.cmake")
+include("${SOURCEMETA_UTILITIES_DIRECTORY}/compiler/simd.cmake")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/compiler/sanitizer.cmake")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/compiler/options.cmake")
 include("${SOURCEMETA_UTILITIES_DIRECTORY}/options/enum.cmake")

cmake/common/compiler/simd.cmake

@@ -0,0 +1,40 @@
+macro(sourcemeta_enable_simd)
+  # Attempt to enable SIMD (SSE/AVX/NEON)
+  include(CheckCXXCompilerFlag)
+  if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86|AMD64")
+    if(MSVC)
+      check_cxx_compiler_flag("/arch:AVX2" COMPILER_SUPPORTS_AVX2)
+      if(COMPILER_SUPPORTS_AVX2)
+        message(STATUS "Enabling SIMD AVX2")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /arch:AVX2")
+      elseif(NOT CMAKE_CL_64)
+        message(STATUS "Enabling SIMD SSE2")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /arch:SSE2")
+      endif()
+    else()
+      check_cxx_compiler_flag("-mavx2" COMPILER_SUPPORTS_AVX2)
+      if(COMPILER_SUPPORTS_AVX2)
+        message(STATUS "Enabling SIMD AVX2")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx2")
+      else()
+        check_cxx_compiler_flag("-msse4.2" COMPILER_SUPPORTS_SSE42)
+        if(COMPILER_SUPPORTS_SSE42)
+          message(STATUS "Enabling SIMD SSE4.2")
+          set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.2")
+        else()
+          check_cxx_compiler_flag("-msse2" COMPILER_SUPPORTS_SSE2)
+          if(COMPILER_SUPPORTS_SSE2)
+            message(STATUS "Enabling SIMD SSE2")
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse2")
+          endif()
+        endif()
+      endif()
+    endif()
+  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm64|aarch64" AND NOT MSVC)
+    check_cxx_compiler_flag("-march=armv8-a+fp+simd" COMPILER_SUPPORTS_NEON)
+    if(COMPILER_SUPPORTS_NEON)
+      message(STATUS "Enabling SIMD NEON")
+      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=armv8-a+fp+simd")
+    endif()
+  endif()
+endmacro()

cmake/common/defaults.cmake

@@ -109,42 +109,3 @@ if(CMAKE_BUILD_TYPE STREQUAL "Release")
     set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -flto=full")
   endif()
 endif()
-
-# Attempt to enable SIMD (SSE/AVX/NEON)
-include(CheckCXXCompilerFlag)
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86|AMD64")
-  if(MSVC)
-    check_cxx_compiler_flag("/arch:AVX2" COMPILER_SUPPORTS_AVX2)
-    if(COMPILER_SUPPORTS_AVX2)
-      message(STATUS "Enabling SIMD AVX2")
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /arch:AVX2")
-    elseif(NOT CMAKE_CL_64)
-      message(STATUS "Enabling SIMD SSE2")
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /arch:SSE2")
-    endif()
-  else()
-    check_cxx_compiler_flag("-mavx2" COMPILER_SUPPORTS_AVX2)
-    if(COMPILER_SUPPORTS_AVX2)
-      message(STATUS "Enabling SIMD AVX2")
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx2")
-    else()
-      check_cxx_compiler_flag("-msse4.2" COMPILER_SUPPORTS_SSE42)
-      if(COMPILER_SUPPORTS_SSE42)
-        message(STATUS "Enabling SIMD SSE4.2")
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.2")
-      else()
-        check_cxx_compiler_flag("-msse2" COMPILER_SUPPORTS_SSE2)
-        if(COMPILER_SUPPORTS_SSE2)
-          message(STATUS "Enabling SIMD SSE2")
-          set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse2")
-        endif()
-      endif()
-    endif()
-  endif()
-elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm64|aarch64" AND NOT MSVC)
-  check_cxx_compiler_flag("-march=armv8-a+fp+simd" COMPILER_SUPPORTS_NEON)
-  if(COMPILER_SUPPORTS_NEON)
-    message(STATUS "Enabling SIMD NEON")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=armv8-a+fp+simd")
-  endif()
-endif()