Does a TRIE-EXACT only pattern do unnecessary work?

[richardleach]

Description
If you run: perl -e 'use re q|debug|; my $x = "x" x 10; 1 while $x =~ /xx|ab/aag;',
the pattern has compiled to a TRIE-EXACT node:

Compiling REx "xx|ab"
Final program:
   1: TRIE-EXACT[ax] (9)
      <xx> 
      <ab> 
   9: END (0)

The output for each match is something like:

stclass AHOCORASICK-EXACT[ax] minlen 2 
Matching REx "xx|ab" against "xxxxxxxxxx"
Matching stclass AHOCORASICK-EXACT[ax] against "xxxxxxxxxx" (10 bytes)
   0 <> <xxxxxxxxxx>         |   0|  Charid:  1 CP:  78 State:    1, word=0 - legal
   1 <x> <xxxxxxxxx>         |   0|  Charid:  1 CP:  78 State:    2, word=0 - legal
   2 <xx> <xxxxxxxx>         |   0|  Charid:  1 CP:  78 State:    3, word=1 - accepting
Matches word #1 at position 0. Trying full pattern...
   0 <> <xxxxxxxxxx>         |   0| 1:TRIE-EXACT[ax](9)
   0 <> <xxxxxxxxxx>         |   0| TRIE: State:    1 Accepted: N TRIE: Charid:  1 CP:  78 After State:    2
   1 <x> <xxxxxxxxx>         |   0| TRIE: State:    2 Accepted: N TRIE: Charid:  1 CP:  78 After State:    3
   2 <xx> <xxxxxxxx>         |   0| TRIE: State:    3 Accepted: Y TRIE: Charid:  0 CP:   0 After State:    0
                             |   0| TRIE: got 1 possible matches
                             |   0| TRIE matched word #1, continuing
                             |   0| TRIE: only one match left, short-circuiting: #1 <xx>
   2 <xx> <xxxxxxxx>         |   0| 9:END(0)
Match successful!

Is it necessary to try the full TRIE-EXACT pattern when in effect, AHOCORASICK-EXACT[ax] has already found a whole pattern match?

Perl configuration
blead

[richardleach]

(The likely place to put a shortcut would be immediately prior to the regtry call in the AHOCORASICK cases within S_find_byclass. If someone was to investigate that possibility, I wonder if going the whole hog to a dedicated pp_match_simple_trie would be worth it for simple tries like this one.)

[iabyn]

On Sun, Oct 19, 2025 at 04:37:48PM -0700, Richard Leach wrote: I wonder if going the whole hog to a dedicated pp_match_simple_trie would be worth it for simple tries like this one.)

Please, no!