Fix compilation errors if host does not support AVX2 (#50316)

* Fix compilation errors if host does not support AVX2

* Add comments to empty preprocessor branches

* Explicitly ask for architecture support

* Apply -march-native only on GCC

* Make sure if clang on x64 would be used
it actually pass -march=native, otherwise AVX2 would not be enabled.

* Ask test use AVX2 when run on Windows.

src/tests/Interop/PInvoke/Generics/CMakeLists.txt

@@ -17,6 +17,16 @@ if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   # The ABI for passing parameters with 32-byte alignment has changed in GCC 4.6
   add_compile_options(-Wno-psabi)
 endif()
+if (MSVC)
+  # The MSVC require explicitly ask for AVX2 so define would be present.
+  add_compile_options(/arch:AVX2)
+else()
+  if (NOT CLR_CMAKE_TARGET_ARCH_ARM64 AND NOT CLR_CMAKE_TARGET_ARCH_ARM)
+    # We need -march=native so we can detect if AVX2 is present.
+    # ARM does not like that option too and it make no sense to have this detection there.
+    add_compile_options(-march=native)
+  endif()
+endif()
 set(SOURCES
   GenericsNative.IUnknown.cpp
   GenericsNative.NullableB.cpp

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256B.cpp

@@ -8,9 +8,15 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
+#elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
 
+#if defined(__AVX2__)
     typedef __m256i Vector256B;
-#elif defined(TARGET_ARMARCH)
+#else
     typedef struct {
         bool e00;
         bool e01;
@@ -45,8 +51,6 @@
         bool e30;
         bool e31;
     } Vector256B;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256B Vector256BValue = { };

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256C.cpp

@@ -8,9 +8,15 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
+#elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
 
+#if defined(__AVX2__)
     typedef __m256i Vector256C;
-#elif defined(TARGET_ARMARCH)
+#else
     typedef struct {
         char16_t e00;
         char16_t e01;
@@ -29,8 +35,6 @@
         char16_t e14;
         char16_t e15;
     } Vector256C;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256C Vector256CValue = { };

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256D.cpp

@@ -8,17 +8,21 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
-
-    typedef __m256d Vector256D;
 #elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
+
+#if defined(__AVX2__)
+    typedef __m256 Vector256D;
+#else
     typedef struct {
         double e00;
         double e01;
         double e02;
         double e03;
     } Vector256D;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256D Vector256DValue = { };

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256F.cpp

@@ -8,9 +8,15 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
+#elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
 
+#if defined(__AVX2__)
     typedef __m256 Vector256F;
-#elif defined(TARGET_ARMARCH)
+#else
     typedef struct {
         float e00;
         float e01;
@@ -21,8 +27,6 @@
         float e06;
         float e07;
     } Vector256F;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256F Vector256FValue = { };

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256L.cpp

@@ -8,17 +8,21 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
+#elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
 
+#if defined(__AVX2__)
     typedef __m256i Vector256L;
-#elif defined(TARGET_ARMARCH)
+#else
     typedef struct {
         int64_t e00;
         int64_t e01;
         int64_t e02;
         int64_t e03;
     } Vector256L;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256L Vector256LValue = { };

src/tests/Interop/PInvoke/Generics/GenericsNative.Vector256U.cpp

@@ -8,9 +8,15 @@
 
 #if defined(TARGET_XARCH)
     #include <immintrin.h>
+#elif defined(TARGET_ARMARCH)
+    // Intentionally empty
+#else
+    #error Unsupported target architecture
+#endif
 
+#if defined(__AVX2__)
     typedef __m256i Vector256U;
-#elif defined(TARGET_ARMARCH)
+#else
     typedef struct {
         uint32_t e00;
         uint32_t e01;
@@ -21,8 +27,6 @@
         uint32_t e06;
         uint32_t e07;
     } Vector256U;
-#else
-    #error Unsupported target architecture
 #endif
 
 static Vector256U Vector256UValue = { };