Changes based on review.

Author: aardvark179

src/main/java/org/truffleruby/cext/UnwrapNode.java

@@ -1,7 +1,9 @@
 package org.truffleruby.cext;
 
+import static org.truffleruby.cext.ValueWrapperManager.TAG_MASK;
 import static org.truffleruby.cext.ValueWrapperManager.LONG_TAG;
 import static org.truffleruby.cext.ValueWrapperManager.OBJECT_TAG;
+import static org.truffleruby.cext.ValueWrapperManager.FALSE_HANDLE;
 
 import org.truffleruby.Layouts;
 
@@ -51,7 +53,7 @@ public Object unwrapNil(long handle) {
 
         @Specialization(guards = "isTaggedLong(handle)")
         public Object unwrapTaggedLong(long handle) {
-            return handle >> 3;
+            return handle >> 1;
         }
 
         @Specialization(guards = "isTaggedObject(handle)")
@@ -60,11 +62,11 @@ public Object unwrapTaggedObject(long handle) {
         }
 
         public boolean isTaggedLong(long handle) {
-            return (handle & 0x7L) == LONG_TAG;
+            return (handle & LONG_TAG) == LONG_TAG;
         }
 
         public boolean isTaggedObject(long handle) {
-            return (handle & 0x7L) == OBJECT_TAG;
+            return handle != FALSE_HANDLE && (handle & TAG_MASK) == OBJECT_TAG;
         }
 
         public static UnwrapNativeNode create() {

src/main/java/org/truffleruby/cext/ValueWrapperManager.java

@@ -15,21 +15,30 @@
 import org.truffleruby.RubyContext;
 import org.truffleruby.collections.LongHashMap;
 import org.truffleruby.extra.ffi.Pointer;
-import org.truffleruby.language.NotProvided;
-import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.object.DynamicObject;
 
 public class ValueWrapperManager {
 
     static final int UNSET_HANDLE = -1;
-    public static final int FALSE_HANDLE = 0;
-    public static final int TRUE_HANDLE = 1;
-    public static final int UNDEF_HANDLE = 2;
-    public static final int NIL_HANDLE = 3;
 
-    public static final int LONG_TAG = 4;
-    public static final int OBJECT_TAG = 7;
+    /*
+     * These constants are taken from ruby.h, and are based on us not tagging doubles.
+     */
+
+    public static final int FALSE_HANDLE = 0x0;
+    public static final int TRUE_HANDLE = 0x2;
+    public static final int NIL_HANDLE = 0x04;
+    public static final int UNDEF_HANDLE = 0x6;
+
+    public static final long LONG_TAG = 1;
+    public static final long OBJECT_TAG = 0;
+
+    public static final long MIN_FIXNUM_VALUE = -(1L << 62);
+    public static final long MAX_FIXNUM_VALUE = (1L << 62) - 1;
+
+    public static final int TAG_BITS = 3;
+    public static final long TAG_MASK = 0x7;
 
     private final LongHashMap<WeakReference<DynamicObject>> handleMap = new LongHashMap<>(1024);
 
@@ -79,7 +88,7 @@ public synchronized void removeFromHandleMap(long handle) {
     public synchronized long createNativeHandle(DynamicObject wrapper) {
         Pointer handlePointer = Pointer.malloc(1);
         long handleAddress = handlePointer.getAddress();
-        if ((handleAddress & 0x7) != 0) {
+        if ((handleAddress & TAG_MASK) != 0) {
             throw new RuntimeException("unaligned malloc for native handle");
         }
         Layouts.VALUE_WRAPPER.setHandle(wrapper, handleAddress);

src/main/java/org/truffleruby/cext/WrapNode.java

@@ -31,13 +31,10 @@ public DynamicObject wrapInt(int value) {
         return wrapLong(value);
     }
 
-    private final long MIN_VALUE = 0xf000_0000_0000_0000L;
-    private final long MAX_VALUE = 0x0fff_ffff_ffff_ffffL;
-
     @Specialization
     public DynamicObject wrapLong(long value) {
-        if (value >= MIN_VALUE && value <= MAX_VALUE) {
-            long val = (value << 3) | LONG_TAG;
+        if (value >= ValueWrapperManager.MIN_FIXNUM_VALUE && value <= ValueWrapperManager.MAX_FIXNUM_VALUE) {
+            long val = (value << 1) | LONG_TAG;
             return Layouts.VALUE_WRAPPER.createValueWrapper(value, val);
         } else {
             return getContext().getValueWrapperManager().longWrapper(value);