speed up feature-checking slightly

When seeing whether the cop hint hash contains the given feature,
Perl_feature_is_enabled only needs to see whether the hint hash ele-
ment exists.  It doesn’t need to turn it into a scalar.

3 files changed, 17 insertions, 10 deletions

diff --git a/hv.c b/hv.c
index 7d5843811e..1c5e6bc776 100644
--- a/hv.c
+++ b/hv.c
@@ -2995,7 +2995,7 @@ Perl_refcounted_he_fetch_pvn(pTHX_ const struct refcounted_he *chain,
     U8 utf8_flag;
     PERL_ARGS_ASSERT_REFCOUNTED_HE_FETCH_PVN;
 
-    if (flags & ~REFCOUNTED_HE_KEY_UTF8)
+    if (flags & ~(REFCOUNTED_HE_KEY_UTF8|REFCOUNTED_HE_EXISTS))
 	Perl_croak(aTHX_ "panic: refcounted_he_fetch_pvn bad flags %"UVxf,
 	    (UV)flags);
     if (!chain)
@@ -3047,9 +3047,15 @@ Perl_refcounted_he_fetch_pvn(pTHX_ const struct refcounted_he *chain,
 	    utf8_flag == (HEK_FLAGS(chain->refcounted_he_hek) & HVhek_UTF8)
 #endif
 	)
-	    return sv_2mortal(refcounted_he_value(chain));
-    }
-    return &PL_sv_placeholder;
+	    return
+		flags & REFCOUNTED_HE_EXISTS
+		    ? (chain->refcounted_he_data[0] & HVrhek_typemask)
+			== HVrhek_delete
+		       ? NULL
+		       : &PL_sv_yes
+		    : sv_2mortal(refcounted_he_value(chain));
+    }
+    return flags & REFCOUNTED_HE_EXISTS ? NULL : &PL_sv_placeholder;
 }
 
 /*
diff --git a/hv.h b/hv.h
index e45460a8c0..05245d58a7 100644
--- a/hv.h
+++ b/hv.h
@@ -509,6 +509,9 @@ struct refcounted_he;
 
 /* flags for the refcounted_he API */
 #define REFCOUNTED_HE_KEY_UTF8		0x00000001
+#ifdef PERL_CORE
+# define REFCOUNTED_HE_EXISTS		0x00000002
+#endif
 
 #ifdef PERL_CORE
 
diff --git a/toke.c b/toke.c
index 643928ddae..286eb96f9a 100644
--- a/toke.c
+++ b/toke.c
@@ -613,13 +613,11 @@ Perl_feature_is_enabled(pTHX_ const char *const name, STRLEN namelen,
     memcpy(&he_name[8 + 2*negate], name, namelen);
 
     return
-	(
-	    cop_hints_fetch_pvn(
-		PL_curcop, he_name, 8 + 2*negate + namelen, 0, 0
-	    )
-	    != &PL_sv_placeholder
+	!cop_hints_fetch_pvn(
+	    PL_curcop, he_name, 8 + 2*negate + namelen, 0,
+	    REFCOUNTED_HE_EXISTS
 	)
-	!= negate;
+	!= !negate;
 }
 
 /*