[compiler-rt] [FMV][AArch64] Add initial AT_HWCAP3 / AT_HWCAP4 support (PR #161595)

[Brad Smith via llvm-commits]

================
@@ -190,3 +190,19 @@
 #ifndef HWCAP2_CSSC
 #define HWCAP2_CSSC (1UL << 34)
 #endif
+
+#ifndef AT_HWCAP3
+#if defined(__linux__) || defined(__ANDROID__)
----------------
brad0 wrote:

> We don't seem to care for non linux/android for other macros like AT_HWCAP and AT_HWCAP2 above. I couldn't find the values 38 and 39 for AT_HWCAP3/AT_HWCAP4 can you shed some light?

Only because *BSD's include sys/auxv.h where as for Linux that does not appear to be the case. AT_HWCAP / AT_HWCAP2 are guaranteed to be defined for the *BSD's if the functionality is there, not so for 3 and 4. Those values are for *BSD's.

https://github.com/llvm/llvm-project/pull/161595