[AArch64] Add LSE support for Windows.

Change-Id: Ic639af3d799163fca829d6f37f830ccec63ab453

Author: DanielKristofKiss

compiler-rt/lib/builtins/cpu_model/aarch64.c

@@ -48,6 +48,8 @@ _Bool __aarch64_have_lse_atomics
 #elif defined(__linux__) && __has_include(<sys/auxv.h>)
 #include "aarch64/hwcap.inc"
 #include "aarch64/lse_atomics/getauxval.inc"
+#elif defined(_WIN32)
+#include "aarch64/lse_atomics/windows.inc"
 #else
 // When unimplemented, we leave __aarch64_have_lse_atomics initialized to false.
 #endif

compiler-rt/lib/builtins/cpu_model/aarch64/lse_atomics/windows.inc

@@ -0,0 +1,12 @@
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <processthreadsapi.h>
+
+#ifndef PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE    34
+#endif
+
+static void CONSTRUCTOR_ATTRIBUTE init_have_lse_atomics(void) {
+  if(IsProcessorFeaturePresent(PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE))
+    __aarch64_have_lse_atomics = true;
+}