Use march=native with clang on MacOS

Author: mhucka

pybind_interface/avx2/CMakeLists.txt

@@ -17,6 +17,10 @@ project(qsim)
 
 IF (WIN32)
     add_compile_options(/arch:AVX2)
+ELSEIF(APPLE AND NOT CMAKE_APPLE_SILICON_PROCESSOR)
+    # On Intel MacOS, CMake detects AVX* but clang doesn't recognize -mavx2.
+    # Using arch=native should turn on the features if they're available.
+    add_compile_options(-march=native)
 ELSE()
     add_compile_options(-mavx2 -mfma)
 ENDIF()

pybind_interface/avx512/CMakeLists.txt

@@ -17,6 +17,11 @@ project(qsim)
 
 IF (WIN32)
     add_compile_options(/arch:AVX512)
+ELSEIF(APPLE AND NOT CMAKE_APPLE_SILICON_PROCESSOR
+       AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    # On Intel Macs CMake detects AVX but clang doesn't recognize -mavx512.
+    # Using arch=native should turn on the features if they're available.
+    add_compile_options(-march=native)
 ELSE()
     add_compile_options(-mavx512f -mbmi2)
 ENDIF()