Print out the match string's encoding in instrumented output.

Also, fix `RegexpCacheKey` to use the encoding of the regexp rather than the string being matched against. By storing the encoding of the string being matched against in `MatchInfo`, we'll have separate entries for matches that share the same regexp instance, but different match string encodings. That's ultimately what we want in order to gain better insights into how regexps are being used in the application.

Author: nirvdrum

src/main/java/org/truffleruby/core/regexp/TruffleRegexpNodes.java

@@ -28,6 +28,7 @@
 import com.oracle.truffle.api.profiles.IntValueProfile;
 import com.oracle.truffle.api.profiles.LoopConditionProfile;
 import org.graalvm.collections.Pair;
+import org.jcodings.Encoding;
 import org.jcodings.specific.ASCIIEncoding;
 import org.jcodings.specific.USASCIIEncoding;
 import org.jcodings.specific.UTF8Encoding;
@@ -86,11 +87,11 @@ public class TruffleRegexpNodes {
     private static void instrumentMatch(ConcurrentHashMap<MatchInfo, AtomicInteger> metricsMap, RubyRegexp regexp,
             Object string, boolean fromStart) {
         Rope source = regexp.source;
-        RubyEncoding enc = RubyStringLibrary.getUncached().getEncoding(string);
         RegexpOptions options = regexp.options;
         TruffleRegexpNodes.MatchInfo matchInfo = new TruffleRegexpNodes.MatchInfo(
-                new RegexpCacheKey(source, enc, options, Hashing.NO_SEED),
-                fromStart);
+                new RegexpCacheKey(source, regexp.encoding, options, Hashing.NO_SEED),
+                fromStart,
+                RubyStringLibrary.getUncached().getEncoding(string));
         ConcurrentOperations.getOrCompute(metricsMap, matchInfo, x -> new AtomicInteger()).incrementAndGet();
     }
 
@@ -737,11 +738,13 @@ static final class MatchInfo {
 
         private final RegexpCacheKey regexpInfo;
         private final boolean matchStart;
+        private final RubyEncoding matchEncoding;
 
-        MatchInfo(RegexpCacheKey regexpInfo, boolean matchStart) {
+        MatchInfo(RegexpCacheKey regexpInfo, boolean matchStart, RubyEncoding matchEncoding) {
             assert regexpInfo != null;
             this.regexpInfo = regexpInfo;
             this.matchStart = matchStart;
+            this.matchEncoding = matchEncoding;
         }
 
         @Override
@@ -760,12 +763,17 @@ public boolean equals(Object obj) {
             }
 
             MatchInfo other = (MatchInfo) obj;
-            return matchStart == other.matchStart && regexpInfo.equals(other.regexpInfo);
+            return matchStart == other.matchStart && matchEncoding == other.matchEncoding &&
+                    regexpInfo.equals(other.regexpInfo);
         }
 
         @Override
         public String toString() {
-            return String.format("Match (%s, fromStart = %s)", regexpInfo, matchStart);
+            return String.format(
+                    "Match (%s, fromStart = %s, encoding = %s)",
+                    regexpInfo,
+                    matchStart,
+                    RopeOperations.decodeOrEscapeBinaryRope(matchEncoding.name.rope));
         }
     }