Remove encodingConversation since it's always true

Author: wildmaples

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

@@ -350,7 +350,7 @@ protected boolean initialized(RubyRegexp regexp) {
         }
     }
 
-    @Primitive(name = "regexp_match_in_region", lowerFixnum = { 2, 3, 6 })
+    @Primitive(name = "regexp_match_in_region", lowerFixnum = { 2, 3, 5 })
     public abstract static class MatchInRegionNode extends PrimitiveArrayArgumentsNode {
 
         /** Matches a regular expression against a string over the specified range of characters.
@@ -366,20 +366,12 @@ public abstract static class MatchInRegionNode extends PrimitiveArrayArgumentsNo
          * @param atStart Whether to only match at the beginning of the string, if false then the regexp can have any
          *            amount of prematch.
          *
-         * @param encodingConversion Whether to attempt encoding conversion of the regexp to match the string
-         *
          * @param startPos The position within the string which the matcher should consider the start. Setting this to
          *            the from position allows scanners to match starting partway through a string while still setting
          *            atStart and thus forcing the match to be at the specific starting position. */
         @Specialization(guards = "libString.isRubyString(string)")
         protected Object matchInRegion(
-                RubyRegexp regexp,
-                Object string,
-                int fromPos,
-                int toPos,
-                boolean atStart,
-                boolean encodingConversion,
-                int startPos,
+                RubyRegexp regexp, Object string, int fromPos, int toPos, boolean atStart, int startPos,
                 @Cached RopeNodes.BytesNode bytesNode,
                 @Cached TruffleRegexpNodes.MatchNode matchNode,
                 @CachedLibrary(limit = "2") RubyStringLibrary libString) {

src/main/ruby/truffleruby/core/truffle/regexp_operations.rb

@@ -78,7 +78,7 @@ def self.match_in_region(re, str, from, to, at_start, encoding_conversion, start
       elsif USE_TRUFFLE_REGEX
         match_in_region_tregex(re, str, from, to, at_start, encoding_conversion, start)
       else
-        Primitive.regexp_match_in_region(re, str, from, to, at_start, encoding_conversion, start)
+        Primitive.regexp_match_in_region(re, str, from, to, at_start, start)
       end
     end
 
@@ -89,7 +89,7 @@ def self.match_in_region_compare_engines(re, str, from, to, at_start, encoding_c
         md1 = e
       end
       begin
-        md2 = Primitive.regexp_match_in_region(re, str, from, to, at_start, encoding_conversion, start)
+        md2 = Primitive.regexp_match_in_region(re, str, from, to, at_start, start)
       rescue => e
         md2 = e
       end
@@ -115,7 +115,7 @@ def self.match_in_region_tregex(re, str, from, to, at_start, encoding_conversion
         regex_result = compiled_regex.execBytes(str_bytes, from)
       end
       if bail_out
-        return Primitive.regexp_match_in_region(re, str, from, to, at_start, encoding_conversion, start)
+        return Primitive.regexp_match_in_region(re, str, from, to, at_start, start)
       elsif regex_result.isMatch
         starts = []
         ends = []