regen/regcharclass.pl: Improve the generated code

This is a small improvement when a consecutive group of U8 code points
begins at 0 or ends at 255.  These end points are physically impossible
of being exceeded, so there is no need to test for that end of the
range.  In several places this causes a mask operation to not be
generated.

1 files changed, 15 insertions, 0 deletions

diff --git a/regen/regcharclass.pl b/regen/regcharclass.pl
index 002cd0f6a9..1f780a48f5 100755
--- a/regen/regcharclass.pl
+++ b/regen/regcharclass.pl
@@ -1097,6 +1097,21 @@ sub _cond_as_str {
             $ranges[$i] =           # Trivial case: single element range
                     sprintf "$self->{val_fmt} == $test", $ranges[$i]->[0];
         }
+        elsif ($ranges[$i]->[0] == 0) {
+            # If the range matches all 256 possible bytes, it is trivially
+            # true.
+            return 1 if $ranges[0]->[1] == 0xFF;    # @ranges must be 1 in
+                                                    # this case
+            $ranges[$i] = sprintf "( $test <= $self->{val_fmt} )",
+                                                               $ranges[$i]->[1];
+        }
+        elsif ($ranges[$i]->[1] == 255) {
+
+            # Similarly the max possible is 255, so can omit an upper bound
+            # test if the calculated max is the max possible one.
+            $ranges[$i] = sprintf "( $test >= $self->{val_fmt} )",
+                                                                $ranges[0]->[0];
+        }
         else {
             my $output = "";