Merge pull request #4286 from facebook/visual_clang_avx2

Fix Visual + ClangCL + AVX2 compilation

.github/workflows/dev-short-tests.yml

@@ -362,6 +362,8 @@ jobs:
           - generator: "MinGW Makefiles"
           - generator: "Visual Studio 17 2022"
             flags: "-T ClangCL"
+          - generator: "Visual Studio 17 2022"
+            flags: "-T ClangCL -A x64 -DCMAKE_C_FLAGS=/arch:AVX2"
     runs-on: windows-2022
     steps:
     - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # tag=v4.1.1

lib/common/compiler.h

@@ -302,10 +302,10 @@ MEM_STATIC int ZSTD_isPower2(size_t u) {
 
 #ifndef ZSTD_ALIGNED
 /* C90-compatible alignment macro (GCC/Clang). Adjust for other compilers if needed. */
-# if defined(__GNUC__)
+# if defined(__GNUC__) || defined(__clang__)
 #  define ZSTD_ALIGNED(a) __attribute__((aligned(a)))
 # elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) /* C11 */
-#  define ZSTD_ALIGNED(a) alignas(a)
+#  define ZSTD_ALIGNED(a) _Alignas(a)
 #elif defined(_MSC_VER)
 #  define ZSTD_ALIGNED(n) __declspec(align(n))
 # else