teach parrot and jvm about zerowidth literals

Author: timo

src/vm/jvm/QAST/Compiler.nqp

@@ -4951,10 +4951,12 @@ class QAST::CompilerJAST {
             $TYPE_STR, 'regionMatches', 'Z', 'Z', 'Integer', $TYPE_STR, 'Integer', 'Integer' ));
         $il.append(JAST::Instruction.new( :op($node.negate ?? 'ifne' !! 'ifeq'), %*REG<fail> ));
 
-        $il.append(JAST::Instruction.new( :op('lload'), %*REG<pos> ));
-        $il.append(JAST::PushIVal.new( :value($litlen) ));
-        $il.append($LADD);
-        $il.append(JAST::Instruction.new( :op('lstore'), %*REG<pos> ));
+        unless $node.subtype eq 'zerowidth' {
+            $il.append(JAST::Instruction.new( :op('lload'), %*REG<pos> ));
+            $il.append(JAST::PushIVal.new( :value($litlen) ));
+            $il.append($LADD);
+            $il.append(JAST::Instruction.new( :op('lstore'), %*REG<pos> ));
+        }
 
         $il;
     }

src/vm/parrot/QAST/Compiler.nqp

@@ -1473,7 +1473,7 @@ class QAST::Compiler is HLL::Compiler {
             $ops.push_pirop('nqp_string_equal_at', '$I11', %*REG<tgt>, $litpost, %*REG<pos>);
             $ops.push_pirop($cmpop,   '$I11', 1, %*REG<fail>);
         }
-        $ops.push_pirop('add',    %*REG<pos>, $litlen);
+        $ops.push_pirop('add',    %*REG<pos>, $litlen) unless $node.subtype eq 'zerowidth';
         $ops;
     }