src/jdk.vm.ci/share/classes/jdk.vm.ci.hotspot.amd64/src/jdk/vm/ci/hotspot/amd64/AMD64HotSpotRegisterConfig.java

@@ -43,10 +43,11 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 import jdk.vm.ci.code.Architecture;
 import jdk.vm.ci.code.CallingConvention;
 import jdk.vm.ci.code.CallingConvention.Type;

@@ -117,18 +118,21 @@
      * Some ABIs (e.g. Windows) require a so-called "home space", that is a save area on the stack
      * to store the argument registers
      */
     private final boolean needsNativeStackHomeSpace;
 
+    private static final Register[] reservedRegisters = {rsp, r15};
+
     private static Register[] initAllocatable(Architecture arch, boolean reserveForHeapBase) {
         Register[] allRegisters = arch.getAvailableValueRegisters();
-        Register[] registers = new Register[allRegisters.length - (reserveForHeapBase ? 3 : 2)];
+        Register[] registers = new Register[allRegisters.length - reservedRegisters.length - (reserveForHeapBase ? 1 : 0)];
+        List<Register> reservedRegistersList = Arrays.asList(reservedRegisters);
 
         int idx = 0;
         for (Register reg : allRegisters) {
-            if (reg.equals(rsp) || reg.equals(r15)) {
-                // skip stack pointer and thread register
+            if (reservedRegistersList.contains(reg)) {
+                // skip reserved registers
                 continue;
             }
             if (reserveForHeapBase && reg.equals(r12)) {
                 // skip heap base register
                 continue;