[libunwind] [libunwind] Add SME detection for Apple platforms (PR #193630)

[Brad Smith via cfe-commits]

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@@ -1940,7 +1943,15 @@ class _LIBUNWIND_HIDDEN Registers_arm64 {
       _LIBUNWIND_ABORT("SME ZA disable failed");
   }
 
-#if defined(_LIBUNWIND_HAVE_GETAUXVAL)
+#if defined(__APPLE__)
+  static bool checkHasSME() {
+    int has_sme = 0;
+    size_t size = sizeof(has_sme);
+    if (!sysctlbyname("hw.optional.arm.FEAT_SME", &has_sme, &size, NULL, 0))
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brad0 wrote:

Thanks!

https://github.com/llvm/llvm-project/pull/193630