Profile the encoding argument in String#force_encoding

Author: eregon

src/main/java/org/truffleruby/core/string/StringNodes.java

@@ -1357,39 +1357,46 @@ protected RubyString sameEncoding(RubyString string, RubyEncoding newEncoding) {
         @Specialization(guards = { "encoding != newEncoding", "tstring.isImmutable()" })
         protected RubyString immutable(RubyString string, RubyEncoding newEncoding,
                 @Cached RubyStringLibrary libString,
+                @Cached RubyStringLibrary profileEncoding,
                 @Cached TruffleString.ForceEncodingNode forceEncodingNode,
                 @Bind("string.tstring") AbstractTruffleString tstring,
                 @Bind("libString.getEncoding(string)") RubyEncoding encoding) {
-            var newTString = forceEncodingNode.execute(tstring, encoding.tencoding, newEncoding.tencoding);
-            string.setTString(newTString, newEncoding);
+            var newEncodingProfiled = profileEncoding.profileEncoding(newEncoding);
+            var newTString = forceEncodingNode.execute(tstring, encoding.tencoding, newEncodingProfiled.tencoding);
+            string.setTString(newTString, newEncodingProfiled);
             return string;
         }
 
         @Specialization(
                 guards = { "encoding != newEncoding", "!tstring.isImmutable()", "!tstring.isNative()" })
         protected RubyString mutableManaged(RubyString string, RubyEncoding newEncoding,
                 @Cached RubyStringLibrary libString,
+                @Cached RubyStringLibrary profileEncoding,
                 @Cached MutableTruffleString.ForceEncodingNode forceEncodingNode,
                 @Bind("string.tstring") AbstractTruffleString tstring,
                 @Bind("libString.getEncoding(string)") RubyEncoding encoding) {
-            var newTString = forceEncodingNode.execute(tstring, encoding.tencoding, newEncoding.tencoding);
-            string.setTString(newTString, newEncoding);
+            var newEncodingProfiled = profileEncoding.profileEncoding(newEncoding);
+            var newTString = forceEncodingNode.execute(tstring, encoding.tencoding, newEncodingProfiled.tencoding);
+            string.setTString(newTString, newEncodingProfiled);
             return string;
         }
 
         @Specialization(
                 guards = { "encoding != newEncoding", "!tstring.isImmutable()", "tstring.isNative()" })
         protected RubyString mutableNative(RubyString string, RubyEncoding newEncoding,
                 @Cached RubyStringLibrary libString,
+                @Cached RubyStringLibrary profileEncoding,
                 @Cached TruffleString.GetInternalNativePointerNode getInternalNativePointerNode,
                 @Cached MutableTruffleString.FromNativePointerNode fromNativePointerNode,
                 @Bind("string.tstring") AbstractTruffleString tstring,
                 @Bind("libString.getEncoding(string)") RubyEncoding encoding) {
+            var newEncodingProfiled = profileEncoding.profileEncoding(newEncoding);
             var currentEncoding = encoding.tencoding;
             var pointer = (Pointer) getInternalNativePointerNode.execute(tstring, currentEncoding);
             var byteLength = tstring.byteLength(currentEncoding);
-            var newTString = fromNativePointerNode.execute(pointer, 0, byteLength, newEncoding.tencoding, false);
-            string.setTString(newTString, newEncoding);
+            var newTString = fromNativePointerNode.execute(pointer, 0, byteLength, newEncodingProfiled.tencoding,
+                    false);
+            string.setTString(newTString, newEncodingProfiled);
             return string;
         }
 

src/main/java/org/truffleruby/language/library/RubyStringLibrary.java

@@ -49,6 +49,8 @@ public final TruffleString.Encoding getTEncoding(Object object) {
 
     public abstract int byteLength(Object object);
 
+    public abstract RubyEncoding profileEncoding(RubyEncoding encoding);
+
     static final class Cached extends RubyStringLibrary {
 
         @CompilationFinal private boolean seenMutable, seenImmutable, seenOther;
@@ -123,6 +125,28 @@ private AbstractTruffleString specializeGetTString(Object object) {
             }
         }
 
+        public RubyEncoding profileEncoding(RubyEncoding encoding) {
+            var localCachedEncoding = this.cachedEncoding;
+            if (encoding == localCachedEncoding) {
+                return (RubyEncoding) localCachedEncoding;
+            } else if (localCachedEncoding == GENERIC) {
+                return encoding;
+            } else {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                return specializeProfileEncoding(encoding);
+            }
+        }
+
+        private RubyEncoding specializeProfileEncoding(RubyEncoding encoding) {
+            var localCachedEncoding = this.cachedEncoding;
+            if (localCachedEncoding == null) {
+                this.cachedEncoding = encoding;
+            } else if (encoding != localCachedEncoding) {
+                this.cachedEncoding = GENERIC;
+            }
+            return encoding;
+        }
+
         @Override
         public RubyEncoding getEncoding(Object object) {
             final RubyEncoding encoding;
@@ -135,15 +159,7 @@ public RubyEncoding getEncoding(Object object) {
                 return specializeGetEncoding(object);
             }
 
-            var localCachedEncoding = this.cachedEncoding;
-            if (encoding == localCachedEncoding) {
-                return (RubyEncoding) localCachedEncoding;
-            } else if (localCachedEncoding == GENERIC) {
-                return encoding;
-            } else {
-                CompilerDirectives.transferToInterpreterAndInvalidate();
-                return specializeGetEncoding(object);
-            }
+            return profileEncoding(encoding);
         }
 
         private RubyEncoding specializeGetEncoding(Object object) {
@@ -158,13 +174,7 @@ private RubyEncoding specializeGetEncoding(Object object) {
                 throw CompilerDirectives.shouldNotReachHere();
             }
 
-            var localCachedEncoding = this.cachedEncoding;
-            if (localCachedEncoding == null) {
-                this.cachedEncoding = encoding;
-            } else if (encoding != localCachedEncoding) {
-                this.cachedEncoding = GENERIC;
-            }
-            return encoding;
+            return specializeProfileEncoding(encoding);
         }
 
         @Override
@@ -193,6 +203,7 @@ static final class Uncached extends RubyStringLibrary {
 
         @Override
         public boolean seen(Object object) {
+            CompilerAsserts.neverPartOfCompilation("Only behind @TruffleBoundary");
             assert object instanceof RubyString || object instanceof ImmutableRubyString;
             return true;
         }
@@ -215,6 +226,12 @@ public AbstractTruffleString getTString(Object object) {
             }
         }
 
+        @Override
+        public RubyEncoding profileEncoding(RubyEncoding encoding) {
+            CompilerAsserts.neverPartOfCompilation("Only behind @TruffleBoundary");
+            return encoding;
+        }
+
         @Override
         public RubyEncoding getEncoding(Object object) {
             CompilerAsserts.neverPartOfCompilation("Only behind @TruffleBoundary");