Initial fixes for Apple silicon (#2978)

* Initial fixes for Apple silicon

Doesn't work yet

* assume vec4 is supported on apple

* Trust the user with env variables

* Fix macos-version-min logic

CMakeLists.txt

@@ -110,7 +110,7 @@ IF(APPLE)
         SET (CMAKE_OSX_DEPLOYMENT_TARGET "10.7" CACHE STRING "The minimum version of OS X to support" FORCE)
     ENDIF (NOT CMAKE_OSX_DEPLOYMENT_TARGET)
     IF (NOT CMAKE_OSX_ARCHITECTURES)
-        SET (CMAKE_OSX_ARCHITECTURES "x86_64" CACHE STRING "The processor architectures to build for" FORCE)
+        SET (CMAKE_OSX_ARCHITECTURES "${CMAKE_SYSTEM_PROCESSOR}" CACHE STRING "The processor architectures to build for" FORCE)
     ENDIF (NOT CMAKE_OSX_ARCHITECTURES)
     IF (NOT CMAKE_OSX_SYSROOT)
         EXECUTE_PROCESS(COMMAND "xcrun" "--show-sdk-path" OUTPUT_VARIABLE XCRUN_OSX_SYSROOT RESULT_VARIABLE XCRUN_OSX_SYSROOT_STATUS OUTPUT_STRIP_TRAILING_WHITESPACE)
@@ -123,7 +123,10 @@ IF(APPLE)
 
     # Improve the linking behavior of Mac libraries
     SET (CMAKE_INSTALL_NAME_DIR "@rpath")
-    SET(EXTRA_COMPILE_FLAGS "-msse2 -stdlib=libc++")
+    IF (X86)
+      SET(EXTRA_COMPILE_FLAGS "-msse2")
+    ENDIF()
+    SET(EXTRA_COMPILE_FLAGS "${EXTRA_COMPILE_FLAGS} -stdlib=libc++")
 ELSEIF(MSVC)
     SET(EXTRA_COMPILE_FLAGS)
     # Use warning level 2, not whatever warning level CMake picked.

openmmapi/include/openmm/internal/vectorize_neon.h

@@ -34,7 +34,7 @@
 
 #ifdef __ANDROID__
 #include <cpu-features.h>
-#else
+#elif !defined(__APPLE__)
 #include <sys/auxv.h>
 #include <asm/hwcap.h>
 #endif
@@ -53,7 +53,9 @@ float32x4_t log_ps(float32x4_t);
  * Determine whether ivec4 and fvec4 are supported on this processor.
  */
 static bool isVec4Supported() {
-#ifdef __ANDROID__
+#ifdef __APPLE__
+    return true;
+#elif defined(__ANDROID__)
     uint64_t features = android_getCpuFeatures();
     return (features & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
 #elif defined(__ARM__)

wrappers/python/setup.py

@@ -190,15 +190,19 @@ def buildKeywordDictionary(major_version_num=MAJOR_VERSION_NUM,
         extra_compile_args.append('/EHsc')
     else:
         if platform.system() == 'Darwin':
-            extra_compile_args += ['-stdlib=libc++', '-mmacosx-version-min=10.7']
-            extra_link_args += ['-stdlib=libc++', '-mmacosx-version-min=10.7', '-Wl', '-rpath', openmm_lib_path]
+            extra_compile_args += ['-stdlib=libc++']
+            extra_link_args += ['-stdlib=libc++', '-Wl', '-rpath', openmm_lib_path]
+            if 'MACOSX_DEPLOYMENT_TARGET' not in os.environ and platform.processor() != 'arm':
+                extra_compile_args += ['-mmacosx-version-min=10.7']
+                extra_link_args += ['-mmacosx-version-min=10.7']
             # Hard-code CC and CXX to clang, since gcc/g++ will *not* work with
             # Anaconda, despite the fact that distutils will try to use them.
             # System Python, homebrew, and MacPorts on Macs will always use
             # clang, so this hack should always work and fix issues with users
             # that have GCC installed from MacPorts or homebrew *and* Anaconda
-            os.environ['CC'] = 'clang'
-            os.environ['CXX'] = 'clang++'
+            if 'CC' not in os.environ:
+                os.environ['CC'] = 'clang'
+                os.environ['CXX'] = 'clang++'
 
     library_dirs=[openmm_lib_path]
     include_dirs=openmm_include_path.split(';')