add consting to op C code

Index: compilers/opsc/src/Ops/Trans.pm
===================================================================
--- compilers/opsc/src/Ops/Trans.pm	(revision 46944)
+++ compilers/opsc/src/Ops/Trans.pm	(working copy)
@@ -44,7 +44,7 @@
 
 our %arg_maps := {};
 
-method access_arg($type, $num) { die('...'); }
+method access_arg($type, $dir, $num) { die('...'); }
 
 method restart_address($addr) { die('...'); }
 method restart_offset($offset) { die('...'); }
Index: compilers/opsc/src/Ops/Trans/C.pm
===================================================================
--- compilers/opsc/src/Ops/Trans/C.pm	(revision 46944)
+++ compilers/opsc/src/Ops/Trans/C.pm	(working copy)
@@ -14,15 +14,15 @@
 
     self<num_entries> := 0;
 
-    self<arg_maps> := hash(
+    self<const_arg_maps> := hash(
         :op("cur_opcode[NUM]"),
 
-        :i("IREG(NUM)"),
-        :n("NREG(NUM)"),
-        :p("PREG(NUM)"),
-        :s("SREG(NUM)"),
-        :k("PREG(NUM)"),
-        :ki("IREG(NUM)"),
+        :i("(const INTVAL)IREG(NUM)"),
+        :n("(const NUMVAL)NREG(NUM)"),
+        :p("(const PMC *)PREG(NUM)"),
+        :s("(const STRING *)SREG(NUM)"),
+        :k("(const PMC *)PREG(NUM)"),
+        :ki("(const INTVAL)IREG(NUM)"),
 
         :ic("cur_opcode[NUM]"),
         :nc("CONST(NUM)->u.number"),
@@ -32,6 +32,15 @@
         :kic("cur_opcode[NUM]")
     );
 
+    self<io_arg_maps> := hash(
+        :i("IREG(NUM)"),
+        :n("NREG(NUM)"),
+        :p("PREG(NUM)"),
+        :s("SREG(NUM)"),
+        :k("PREG(NUM)"),
+        :ki("IREG(NUM)"),
+    );
+
     self;
 }
 
@@ -75,9 +84,9 @@
     }
 }
 
-method access_arg($type, $num) {
-    my $access := self<arg_maps>{$type};
-    die("unrecognized arg type '$type'") unless $access;
+method access_arg($type, $dir, $num) {
+    my $access := $dir == 'i' ?? self<const_arg_maps>{$type} !! self<io_arg_maps>{$type};
+    die("unrecognized arg type '$dir $type'") unless $access;
     subst($access, /NUM/, $num);
 }
 
Index: compilers/opsc/src/Ops/Op.pm
===================================================================
--- compilers/opsc/src/Ops/Op.pm	(revision 46944)
+++ compilers/opsc/src/Ops/Op.pm	(working copy)
@@ -141,6 +141,11 @@
     @arg_types[$arg_num];
 }
 
+method arg_dir($arg_num) {
+    my @arg_dirs := self.arg_dirs;
+    @arg_dirs[$arg_num];
+}
+
 method full_name() {
     my $name      := self.name;
     my @arg_types := self.arg_types;
@@ -290,7 +295,7 @@
     # Poor man multis...
     if $what eq 'PAST::Var()' {
         my $n := +$chunk.name;
-        return $trans.access_arg( self.arg_type($n - 1), $n);
+        return $trans.access_arg( self.arg_type($n - 1), self.arg_dir($n - 1), $n);
     }
     elsif $what eq 'PAST::Op()' {
         my $type := $chunk.pasttype;