8261072: AArch64: Fix MacroAssembler::get_thread convention

Co-authored-by: Monica Beckwith <[email protected]>
Backport-of: b670efd

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp

@@ -5811,10 +5811,14 @@ void MacroAssembler::char_array_compress(Register src, Register dst, Register le
 // by the call to JavaThread::aarch64_get_thread_helper() or, indeed,
 // the call setup code.
 //
-// aarch64_get_thread_helper() clobbers only r0, r1, and flags.
+// On Linux, aarch64_get_thread_helper() clobbers only r0, r1, and flags.
+// On other systems, the helper is a usual C function.
 //
 void MacroAssembler::get_thread(Register dst) {
-  RegSet saved_regs = RegSet::range(r0, r1) + BSD_ONLY(RegSet::range(r2, r17)) + lr - dst;
+  RegSet saved_regs =
+    LINUX_ONLY(RegSet::range(r0, r1)  + lr - dst)
+    NOT_LINUX (RegSet::range(r0, r17) + lr - dst);
+
   push(saved_regs, sp);
 
   mov(lr, CAST_FROM_FN_PTR(address, JavaThread::aarch64_get_thread_helper));