Super Slow Support(tm) for 32-bit unicode codepoints in nqp::chars() and nqp::substr(). This increases rakudo's parse time from 57s to nearly ten minutes.

codepoints.diff

diff --git a/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java b/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
index c193007..e1d3418 100644
--- a/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
+++ b/src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java
@@ -2648,7 +2648,7 @@ public final class Ops {
 
     /* String operations. */
     public static long chars(String val) {
-        return val.length();    
+        return val.codePointCount(0, val.length());
     }
     
     public static String lc(String val) {
@@ -2656,7 +2656,7 @@ public final class Ops {
     }
 
     public static String uc(String val) {
-        return val.toUpperCase();    
+        return val.toUpperCase(); // maybe Character.toUpperCase(int codePoint) ? (but this might break ß/SS)
     }
 
     public static String x(String val, long count) {
@@ -2671,8 +2671,16 @@ public final class Ops {
         return valA + valB;
     }
 
+    /**
+     * Creates new String that contains just the given code point.
+     * Version that optimizes for BMP characters.
+     */
     public static String chr(long val) {
-        return (new StringBuffer()).append(Character.toChars((int)val)).toString();
+        if (Character.charCount((int)val) == 1) {
+            return String.valueOf((char) val);
+        } else {
+            return new String(Character.toChars((int)val));
+        }
     }
     
     public static String join(String delimiter, SixModelObject arr, ThreadContext tc) {
@@ -2751,11 +2759,13 @@ public final class Ops {
     }
 
     public static String substr2(String val, long offset) {
-        if (offset >= val.length())
-            return "";
-        if (offset < 0)
-            offset += val.length();
-        return val.substring((int)offset);
+        int length = val.length();
+        if (offset >= length) return "";
+        if (offset == 0)      return val;
+        length = val.codePointCount(0, val.length());
+        if (offset >= length) return "";
+        if (offset < 0)           offset += length;
+        return val.substring( val.offsetByCodePoints(0, (int)offset) );
     }
     
     public static String substr3(String val, long offset, long length) {
@@ -2764,7 +2774,9 @@ public final class Ops {
         int end = (int)(offset + length);
         if (end > val.length())
             end = val.length();
-        return val.substring((int)offset, end);
+        offset = val.offsetByCodePoints(0, (int)offset);
+        end = val.offsetByCodePoints(0, end);
+        return val.substring(val.offsetByCodePoints(0, (int)offset), end);
     }
 
     public static long ordfirst(String str) {