Add GV_NOUNIVERSAL flag to skip UNIVERSAL lookup

For the `isa` infix operator, we can fall back to `sv_derived_from_sv`
instead of looking up UNIVERSAL::isa. Passing GV_NOUNIVERSAL will tell
gv_fetchmeth_internal not to look at UNIVERSAL for the method, and instead
return NULL. Then `Perl_sv_isa_sv` will skip the if block and check
`sv_derived_from_sv` which does the same thing UNIVERSAL::isa would have done.

3 files changed, 3 insertions, 5 deletions

diff --git a/gv.c b/gv.c
index 861f65c237..4660003a53 100644
--- a/gv.c
+++ b/gv.c
@@ -890,7 +890,7 @@ S_gv_fetchmeth_internal(pTHX_ HV* stash, SV* meth, const char* name, STRLEN len,
     }
 
     /* Check UNIVERSAL without caching */
-    if(level == 0 || level == -1) {
+    if((level == 0 || level == -1) && !(flags & GV_NOUNIVERSAL)) {
         candidate = gv_fetchmeth_internal(NULL, meth, name, len, 1,
                                           flags &~GV_SUPER);
         if(candidate) {
diff --git a/gv.h b/gv.h
index 514bac1871..9b465a069d 100644
--- a/gv.h
+++ b/gv.h
@@ -245,6 +245,7 @@ Return the CV from the GV.
 
 /* Flags for gv_fetchmeth_pvn and gv_autoload_pvn*/
 #define GV_SUPER	0x1000	/* SUPER::method */
+#define GV_NOUNIVERSAL  0x2000  /* Skip UNIVERSAL lookup */
 
 /* Flags for gv_autoload_*/
 #define GV_AUTOLOAD_ISMETHOD 1	/* autoloading a method? */
diff --git a/universal.c b/universal.c
index b839e5151d..5932767bdf 100644
--- a/universal.c
+++ b/universal.c
@@ -216,10 +216,7 @@ Perl_sv_isa_sv(pTHX_ SV *sv, SV *namesv)
     if(!SvROK(sv) || !SvOBJECT(SvRV(sv)))
         return FALSE;
 
-    /* TODO: Consider if we want a NOUNIVERSAL flag to skip the
-     * UNIVERSAL lookup
-     */
-    isagv = gv_fetchmeth_pvn(SvSTASH(SvRV(sv)), "isa", 3, -1, 0);
+    isagv = gv_fetchmeth_pvn(SvSTASH(SvRV(sv)), "isa", 3, -1, GV_NOUNIVERSAL);
     if(isagv) {
         dSP;
         CV *isacv = isGV(isagv) ? GvCV(isagv) : (CV *)isagv;