[Truffle] Make better use of shared byte arrays in RopeTable.

This is a bit of an ugly approach, but it works, and we need to revisit the table key class already.
jruby · Mar 24, 2016 · 54efdcd · 54efdcd · nirvdrum · Mar 24, 2016
1 parent 2c8fe8a
commit 54efdcd
Showing 2 changed files with 26 additions and 7 deletions.
diff --git a/test/truffle/compiler/pe/language/defined_pe.rb b/test/truffle/compiler/pe/language/defined_pe.rb
@@ -6,8 +6,8 @@
 # GNU General Public License version 2
 # GNU Lesser General Public License version 2.1
 
-tagged_example "defined?(true) == 'true'", true
-tagged_example "defined?(false) == 'false'", true
-tagged_example "defined?(self) == 'self'", true
-tagged_example "defined?(14) == 'expression'", true
-tagged_example "defined?(14 + 2) == 'expression'", true
+example "defined?(true) == 'true'", true
+example "defined?(false) == 'false'", true
+example "defined?(self) == 'self'", true
+example "defined?(14) == 'expression'", true
+tagged_example "defined?(14 + 2) == 'method'", true
diff --git a/truffle/src/main/java/org/jruby/truffle/core/rope/RopeTable.java b/truffle/src/main/java/org/jruby/truffle/core/rope/RopeTable.java
@@ -44,6 +44,13 @@ public Rope getRope(byte[] bytes, Encoding encoding, CodeRange codeRange) {
             lock.readLock().unlock();
         }
 
+        // The only time we should have a null encoding is if we want to find a rope with the same logical byte[] as
+        // the one supplied to this method. If we've made it this far, no such rope exists, so return null immediately
+        // to back out of the recursive call.
+        if (encoding == null) {
+            return null;
+        }
+
         lock.writeLock().lock();
 
         try {
@@ -57,7 +64,19 @@ public Rope getRope(byte[] bytes, Encoding encoding, CodeRange codeRange) {
                 }
             }
 
-            final Rope rope = RopeOperations.create(bytes, encoding, codeRange);
+            // At this point, we were unable to find a rope with the same bytes and encoding (i.e., a direct match).
+            // However, there may still be a rope with the same byte[] and sharing a direct byte[] can still allow some
+            // reference equality optimizations. So, do another search but with a marker encoding. The only guarantee
+            // we can make about the resulting rope is that it would have the same logical byte[], but that's good enough
+            // for our purposes.
+            final Rope ropeWithSameBytesButDifferentEncoding = getRope(bytes, null ,codeRange);
+
+            final Rope rope;
+            if (ropeWithSameBytesButDifferentEncoding != null) {
+                rope = RopeOperations.create(ropeWithSameBytesButDifferentEncoding.getBytes(), encoding, codeRange);
+            } else {
+                rope = RopeOperations.create(bytes, encoding, codeRange);
+            }
 
             ropesTable.put(key, new WeakReference<>(rope));
 
@@ -89,7 +108,7 @@ public boolean equals(Object o) {
             if (o instanceof Key) {
                 final Key other = (Key) o;
 
-                return encoding == other.encoding && Arrays.equals(bytes, other.bytes);
+                return ((encoding == other.encoding) || (encoding == null)) && Arrays.equals(bytes, other.bytes);
             }
 
             return false;