Add a key flag HVhek_KEYCANONICAL for Perl_hv_common(), which signals that the

key is in canonical form - any key passed encoded in UTF-8 cannot be represented
as bytes, hence the downgrade check can be skipped. Use this internally for
shared hash key scalars, as they are always canonical.

1 files changed, 6 insertions, 2 deletions

diff --git a/hv.c b/hv.c
index b764c5593e..79f59730a9 100644
--- a/hv.c
+++ b/hv.c
@@ -388,8 +388,12 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	if (flags & HVhek_FREEKEY)
 	    Safefree(key);
 	key = SvPV_const(keysv, klen);
-	flags = 0;
 	is_utf8 = (SvUTF8(keysv) != 0);
+	if (SvIsCOW_shared_hash(keysv)) {
+	    flags = HVhek_KEYCANONICAL | (is_utf8 ? HVhek_UTF8 : 0);
+	} else {
+	    flags = 0;
+	}
     } else {
 	is_utf8 = ((flags & HVhek_UTF8) ? TRUE : FALSE);
     }
@@ -595,7 +599,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	}
     }
 
-    if (is_utf8) {
+    if (is_utf8 & !(flags & HVhek_KEYCANONICAL)) {
 	char * const keysave = (char *)key;
 	key = (char*)bytes_from_utf8((U8*)key, &klen, &is_utf8);
         if (is_utf8)