bpo-31671: re: Convert RegexFlag to int before compile (GH-3862)

sre_compile does bit test (e.g. `flags & SRE_FLAG_IGNORECASE`) in loop.
`IntFlag.__and__` and `IntFlag.__new__` made it slower.

So this commit convert it to normal int before passing flags to `sre_compile()`.

1 files changed, 4 insertions, 0 deletions

diff --git a/Lib/re.py b/Lib/re.py
index d772979..abbf8d6 100644
--- a/Lib/re.py
+++ b/Lib/re.py
@@ -275,6 +275,8 @@ _cache = OrderedDict()
 _MAXCACHE = 512
 def _compile(pattern, flags):
     # internal: compile pattern
+    if isinstance(flags, RegexFlag):
+        flags = flags.value
     try:
         return _cache[type(pattern), pattern, flags]
     except KeyError:
@@ -331,6 +333,8 @@ copyreg.pickle(Pattern, _pickle, _compile)
 class Scanner:
     def __init__(self, lexicon, flags=0):
         from sre_constants import BRANCH, SUBPATTERN
+        if isinstance(flags, RegexFlag):
+            flags = flags.value
         self.lexicon = lexicon
         # combine phrases into a compound pattern
         p = []