Introduce SvCANEXISTDELETE in pp.h, which simplify the logic in pp_helem and pp_hslice

3 files changed, 29 insertions, 28 deletions

diff --git a/pp.c b/pp.c
index 0fbc6e48e8..bdbe010f3e 100644
--- a/pp.c
+++ b/pp.c
@@ -4143,31 +4143,28 @@ PP(pp_hslice)
     register HV * const hv = MUTABLE_HV(POPs);
     register const I32 lval = (PL_op->op_flags & OPf_MOD || LVRET);
     const bool localizing = PL_op->op_private & OPpLVAL_INTRO;
-    bool other_magic = FALSE;
+    bool can_preserve = FALSE;
 
     if (localizing) {
         MAGIC *mg;
         HV *stash;
 
-        other_magic = mg_find((const SV *)hv, PERL_MAGIC_env) ||
-            ((mg = mg_find((const SV *)hv, PERL_MAGIC_tied))
-             /* Try to preserve the existenceness of a tied hash
-              * element by using EXISTS and DELETE if possible.
-              * Fallback to FETCH and STORE otherwise */
-             && (stash = SvSTASH(SvRV(SvTIED_obj(MUTABLE_SV(hv), mg))))
-             && gv_fetchmethod_autoload(stash, "EXISTS", TRUE)
-             && gv_fetchmethod_autoload(stash, "DELETE", TRUE));
+	if (SvCANEXISTDELETE(hv) || mg_find((const SV *)hv, PERL_MAGIC_env))
+	    can_preserve = TRUE;
     }
 
     while (++MARK <= SP) {
         SV * const keysv = *MARK;
         SV **svp;
         HE *he;
-        bool preeminent = FALSE;
-
-        if (localizing) {
-            preeminent = SvRMAGICAL(hv) && !other_magic ? 1 :
-                hv_exists_ent(hv, keysv, 0);
+        bool preeminent = TRUE;
+
+        if (localizing && can_preserve) {
+	    /* If we can determine whether the element exist,
+             * try to preserve the existenceness of a tied hash
+             * element by using EXISTS and DELETE if possible.
+             * Fallback to FETCH and STORE otherwise. */
+            preeminent = hv_exists_ent(hv, keysv, 0);
         }
 
         he = hv_fetch_ent(hv, keysv, lval, 0);
diff --git a/pp.h b/pp.h
index 6f0f258278..118c027201 100644
--- a/pp.h
+++ b/pp.h
@@ -500,6 +500,15 @@ True if this op will be the return value of an lvalue subroutine
 =cut */
 #define LVRET ((PL_op->op_private & OPpMAYBE_LVSUB) && is_lvalue_sub())
 
+#define SvCANEXISTDELETE(sv) \
+ (!SvRMAGICAL(sv)            \
+  || ((mg = mg_find((const SV *) sv, PERL_MAGIC_tied))           \
+      && (stash = SvSTASH(SvRV(SvTIED_obj(MUTABLE_SV(sv), mg)))) \
+      && gv_fetchmethod_autoload(stash, "EXISTS", TRUE)          \
+      && gv_fetchmethod_autoload(stash, "DELETE", TRUE)          \
+     )                       \
+  )
+
 /*
  * Local variables:
  * c-indentation-style: bsd
diff --git a/pp_hot.c b/pp_hot.c
index f0c56cf9f5..88fe83814e 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1783,7 +1783,7 @@ PP(pp_helem)
     const U32 defer = PL_op->op_private & OPpLVAL_DEFER;
     SV *sv;
     const U32 hash = (SvIsCOW_shared_hash(keysv)) ? SvSHARED_HASH(keysv) : 0;
-    I32 preeminent = 0;
+    bool preeminent = TRUE;
 
     if (SvTYPE(hv) != SVt_PVHV)
 	RETPUSHUNDEF;
@@ -1791,20 +1791,15 @@ PP(pp_helem)
     if (PL_op->op_private & OPpLVAL_INTRO) {
 	MAGIC *mg;
 	HV *stash;
-	/* does the element we're localizing already exist? */
-	preeminent = /* can we determine whether it exists? */
-	    (    !SvRMAGICAL(hv)
-		|| mg_find((const SV *)hv, PERL_MAGIC_env)
-		|| (     (mg = mg_find((const SV *)hv, PERL_MAGIC_tied))
-			/* Try to preserve the existenceness of a tied hash
-			* element by using EXISTS and DELETE if possible.
-			* Fallback to FETCH and STORE otherwise */
-		    && (stash = SvSTASH(SvRV(SvTIED_obj(MUTABLE_SV(hv), mg))))
-		    && gv_fetchmethod_autoload(stash, "EXISTS", TRUE)
-		    && gv_fetchmethod_autoload(stash, "DELETE", TRUE)
-		)
-	    ) ? hv_exists_ent(hv, keysv, 0) : 1;
+
+	/* If we can determine whether the element exist,
+	 * Try to preserve the existenceness of a tied hash
+	 * element by using EXISTS and DELETE if possible.
+	 * Fallback to FETCH and STORE otherwise. */
+	if (SvCANEXISTDELETE(hv) || mg_find((const SV *)hv, PERL_MAGIC_env))
+	    preeminent = hv_exists_ent(hv, keysv, 0);
     }
+
     he = hv_fetch_ent(hv, keysv, lval && !defer, hash);
     svp = he ? &HeVAL(he) : NULL;
     if (lval) {