test suspected compiler issue around returning with register variable

Author: DanielKristofKiss

libunwind/src/Registers.hpp

@@ -1836,13 +1836,14 @@ class _LIBUNWIND_HIDDEN Registers_arm64 {
   // Authenticate the given pointer and return with the raw value
   // if the authentication is succeeded.
   inline uint64_t auth(uint64_t ptr, uint64_t salt) const {
+    uint64_t ret;
     register uint64_t x17 __asm("x17") = ptr;
     register uint64_t x16 __asm("x16") = salt;
     asm volatile ("hint  0xc" // autia1716
                   : "+r"(x17)
                   : "r"(x16)
                   :);
-
+    ret = x17;
     uint64_t checkValue = ptr;
     // Support for machines without FPAC.
     // Strip the upper bits with `XPACLRI` and compare with the
@@ -1855,7 +1856,7 @@ class _LIBUNWIND_HIDDEN Registers_arm64 {
         : "x30");
     if (x17 != checkValue)
       _LIBUNWIND_ABORT("IP PAC authentication failure");
-    return x17;
+    return ret;
   }
 
   // Sign the PC with the A-KEY and the current salt.