bpo-30340: Enhanced regular expressions optimization. (#1542)

This increased the performance of matching some patterns up to 25 times.

1 files changed, 10 insertions, 5 deletions

diff --git a/Lib/sre_compile.py b/Lib/sre_compile.py
index cebecb93c0..aeb89bcc7b 100644
--- a/Lib/sre_compile.py
+++ b/Lib/sre_compile.py
@@ -20,6 +20,7 @@ _LITERAL_CODES = {LITERAL, NOT_LITERAL}
 _REPEATING_CODES = {REPEAT, MIN_REPEAT, MAX_REPEAT}
 _SUCCESS_CODES = {SUCCESS, FAILURE}
 _ASSERT_CODES = {ASSERT, ASSERT_NOT}
+_UNIT_CODES = _LITERAL_CODES | {ANY, IN}
 
 # Sets of lowercase characters which have the same uppercase.
 _equivalences = (
@@ -125,7 +126,7 @@ def _compile(code, pattern, flags):
         elif op in REPEATING_CODES:
             if flags & SRE_FLAG_TEMPLATE:
                 raise error("internal: unsupported template operator %r" % (op,))
-            elif _simple(av) and op is not REPEAT:
+            if _simple(av[2]):
                 if op is MAX_REPEAT:
                     emit(REPEAT_ONE)
                 else:
@@ -404,10 +405,14 @@ def _bytes_to_codes(b):
     assert len(a) * a.itemsize == len(b)
     return a.tolist()
 
-def _simple(av):
-    # check if av is a "simple" operator
-    lo, hi = av[2].getwidth()
-    return lo == hi == 1 and av[2][0][0] != SUBPATTERN
+def _simple(p):
+    # check if this subpattern is a "simple" operator
+    if len(p) != 1:
+        return False
+    op, av = p[0]
+    if op is SUBPATTERN:
+        return av[0] is None and _simple(av[-1])
+    return op in _UNIT_CODES
 
 def _generate_overlap_table(prefix):
     """