Avoid lots of allocation/boxing with cursors.

Only changed on Moar here, but can do similar thing on other backends.

Author: jnthn

src/QRegex/Cursor.nqp

@@ -1,5 +1,6 @@
 # Some things that all cursors involved in a given parse share.
 my class ParseShared is export {
+    has $!CUR_CLASS;
     has $!orig;
     has str $!target;
     has int $!highwater;
@@ -101,6 +102,7 @@ role NQPCursorRole is export {
         my $new := self.CREATE();
         unless $shared {
             $shared := nqp::create(ParseShared);
+            nqp::bindattr($shared, ParseShared, '$!CUR_CLASS', $?CLASS);
             nqp::bindattr($shared, ParseShared, '$!orig', $orig);
             nqp::bindattr_s($shared, ParseShared, '$!target',
 #?if parrot
@@ -161,6 +163,32 @@ role NQPCursorRole is export {
         }
     }
 
+    # Starts a new Cursor or restarts an existing one. Returns the newly
+    # created Cursor.
+    method !cursor_start() {
+        my $new := nqp::create(self);
+        my $sub := nqp::callercode();
+        # Uncomment following to log cursor creation.
+        #$!shared.log_cc(nqp::getcodename($sub));
+        nqp::bindattr($new, $?CLASS, '$!shared', $!shared);
+        nqp::bindattr($new, $?CLASS, '$!regexsub', nqp::ifnull(nqp::getcodeobj($sub), $sub));
+        if nqp::defined($!restart) {
+            nqp::bindattr_i($new, $?CLASS, '$!pos', $!pos);
+            nqp::bindattr($new, $?CLASS, '$!cstack', nqp::clone($!cstack)) if $!cstack;
+            nqp::getattr_s($!shared, ParseShared, '$!target');
+            nqp::bindattr_i($new, $?CLASS, '$!from', $!from);
+            nqp::bindattr($new, $?CLASS, '$!bstack', nqp::clone($!bstack));
+            $new
+        }
+        else {
+            nqp::bindattr_i($new, $?CLASS, '$!pos', -3);
+            nqp::getattr_s($!shared, ParseShared, '$!target');
+            nqp::bindattr_i($new, $?CLASS, '$!from', $!pos);
+            nqp::bindattr($new, $?CLASS, '$!bstack', nqp::list_i());
+            $new
+        }
+    }
+    
     # Starts a new cursor, returning nothing but the cursor.
     method !cursor_start_cur() {
         my $new := nqp::create(self);

src/vm/moar/QAST/QASTRegexCompilerMAST.nqp

@@ -49,7 +49,6 @@ class QAST::MASTRegexCompiler {
         my $two      := fresh_i();
         my $three    := fresh_i();
         my $four     := fresh_i();
-        my $five     := fresh_i();
         my $P11      := fresh_o();
         my $method   := fresh_o();
         my $tmp      := fresh_o();
@@ -96,7 +95,8 @@ class QAST::MASTRegexCompiler {
 
         my @*RXJUMPS := nqp::list($donelabel);
 
-        my $cstart := fresh_o();
+        my $shared := fresh_o();
+        my $sharedclass := fresh_o();
         my $i19 := fresh_i(); # yes, I know, inheriting the name from ancestor method
         my $i0 := fresh_i();
 
@@ -107,21 +107,20 @@ class QAST::MASTRegexCompiler {
             op('const_i64', $two, ival(2)),
             op('const_i64', $three, ival(3)),
             op('const_i64', $four, ival(4)),
-            op('const_i64', $five, ival(5)),
             op('const_i64', $cclass_word, ival(nqp::const::CCLASS_WORD)),
             op('const_i64', $cclass_newline, ival(nqp::const::CCLASS_NEWLINE)),
-            op('findmeth', $method, $self, sval('!cursor_start_all')),
-            call($method, [ $Arg::obj ], :result($cstart), $self ),
-            op('atpos_o', $cur, $cstart, $zero),
-            op('atpos_o', $tmp, $cstart, $one),
-            op('unbox_s', $tgt, $tmp),
+            op('findmeth', $method, $self, sval('!cursor_start')),
+            call($method, [ $Arg::obj ], :result($cur), $self ),
+            op('findmeth', $shared, $self, sval('!shared')),
+            call($shared, [ $Arg::obj ], :result($shared), $self ),
+            op('getwhat', $sharedclass, $shared),
+            op('getattr_o', $curclass, $shared, $sharedclass, sval('$!CUR_CLASS'), ival(-1)),
+            op('getattr_s', $tgt, $shared, $sharedclass, sval('$!target'), ival(-1)),
             op('flattenropes', $tgt),
-            op('atpos_o', $tmp, $cstart, $two),
-            op('unbox_i', $pos, $tmp),
-            op('atpos_o', $curclass, $cstart, $three),
-            op('atpos_o', $bstack, $cstart, $four),
-            op('atpos_o', $tmp, $cstart, $five),
-            op('unbox_i', $i19, $tmp),
+            op('getattr_i', $pos, $cur, $curclass, sval('$!from'), ival(-1)),
+            op('getattr_o', $bstack, $cur, $curclass, sval('$!bstack'), ival(-1)),
+            op('getattr_o', $tmp, $self, $curclass, sval('$!restart'), ival(-1)),
+            op('isconcrete', $i19, $tmp),
             op('bindlex', $*BLOCK.resolve_lexical('$¢'), $cur),
             op('graphs_s', $eos, $tgt),
             op('eq_i', $i0, $one, $i19),