Read expr tree IR ops order

tools/tiler-table-generator.pl

@@ -13,8 +13,26 @@
 # indirectly create rulenr -> terminal
 # table contains head -> rulenr
 
-my @rules;
+# Read the expression tree node types in correct order
+my @expr_ops;
+{
+    open my $expr_h, '<', 'src/jit/expr.h' or die "Could not open expression definition file";
+    while (<$expr_h>) {
+        last if m/^#define MVM_JIT_IR_OPS\(_\) \\/;
+    }
+    while(!eof($expr_h)) {
+        my $line = <$expr_h>;
+        chomp $line;
+        last unless $line =~ m/\\$/;
+        next unless $line =~ m/_\((\w+), \d+, \d+, \w+\)/;
+        my $op = lc(substr($line, $-[1], $+[1]-$-[1]));
+        push @expr_ops, $op;
+    }
+    close $expr_h;
+}
 
+# Collect rules from the grammar
+my @rules;
 sub add_rule {
     my ($fragment, $terminal, $cost, $depth) = @_;
     my $list = [];
@@ -63,6 +81,30 @@ sub add_rule {
 }
 
 
+#
+# Generate rulesets conservatively.
+#
+# The code generator tries to map tree elements to generation rules.
+# In many cases, a given tree element can be mapped to many rules at
+# the same time (the ruleset). Such rulesets represent the states in
+# the matching DFA. State transitions are effected by means of a
+# three-dimensional table of [ head x ruleset x ruleset ], which is
+# why we want to keep the number of rulesets as small as possible.
+#
+# The smallest number possible is of course only those rulesets that
+# can be generated by the DFA. Thus, we first need to generate the
+# DFA table to find the rulesets required for the DFA table. To solve
+# this circular problem, observe that the rulesets generated by a head
+# can only depend on the terminals that the children of the head refer
+# to. And that it cannot matter *which* ruleset generates these terminals,
+# just as long as *all* terminals are generated by a ruleset.  Hence,
+# we can use topological sort to find the 'generatable' subset of heads,
+# and use these to generate the rulesets by head.
+#
+# I think this can be optimized further by selecting only a single ruleset
+# per terminal candidate ruleset.
+#
+
 my @order;
 my %candidates;
 my @rulesets;
@@ -158,15 +200,15 @@ sub min_cost {
                 my $lc1 = min_cost($rs1, $c1);
                 for my $rs2 (@$cand2) {
                     my $lc2 = min_cost($rs2, $c2);
-                    $table{$head}{$rs1}{$rs2} = [$rule_nr, $lc1, $lc2] if $term eq 'reg';
+                    $table{$head}{$rs1}{$rs2} = [$rule_nr, $lc1, $lc2] if ($term eq 'reg' || $term eq 'void');
                     $trans{$head,$rs1,$rs2}->{$rule_nr} = 1;
                 }
             }
         } else {
             # unary
             for my $rs1 (@$cand1) {
                 my $lc1 = min_cost($rs1, $c1);
-                $table{$head}{$rs1} = [$rule_nr, $lc1] if $term eq 'reg';
+                $table{$head}{$rs1} = [$rule_nr, $lc1] if ($term eq 'reg' || $term eq 'void');
                 $trans{$head,$rs1}->{$rule_nr} = 1;
             }
         }