call_sv, amagic_call: call pp_entersub via runops

These two functions do a slightly odd thing (which has been present
since 5.000) when calling out to a CV: they half fake up an OP_ENTERSUB,
then call pp_entersub() directly, and only then if it returns a non-null
PL_op value, execute the rest of the ops of the sub within a
CALLRUNOPS() loop.

I can't find any particular reason for this. I guess it might make
calling XS subs infinitesimally faster by not have to invoke the runops
loop when only a single op is executed (the entersub), but hardly seems
worth the effort.

Conversely, eliminating this special-case makes the code cleaner, and
it will allow the workarounds planned to be added shortly (to the runops
loops for reference-counted stacks) to work uniformly. Without this
commit, pp_entersub() would get called before runops() has had a chance
to fix up the stack if necessary.

So this commit *fully* populates the fake OP_ENTERSUB (including type
and pp address) then causes pp_entersub to be invoked implicitly from the
runops loop rather than explicitly.

gv.c

@@ -4079,7 +4079,7 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
 
   {
     dSP;
-    BINOP myop;
+    UNOP myop;
     SV* res;
     const bool oldcatch = CATCH_GET;
     I32 oldmark, nret;
@@ -4091,10 +4091,11 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
                     ? G_SCALAR : GIMME_V;
 
     CATCH_SET(TRUE);
-    Zero(&myop, 1, BINOP);
-    myop.op_last = (OP *) &myop;
-    myop.op_next = NULL;
+    Zero(&myop, 1, UNOP);
     myop.op_flags = OPf_STACKED;
+    myop.op_ppaddr = PL_ppaddr[OP_ENTERSUB];
+    myop.op_type = OP_ENTERSUB;
+
 
     switch (gimme) {
         case G_VOID:
@@ -4134,9 +4135,7 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
     PUSHs(MUTABLE_SV(cv));
     PUTBACK;
     oldmark = TOPMARK;
-
-    if ((PL_op = PL_ppaddr[OP_ENTERSUB](aTHX)))
-      CALLRUNOPS(aTHX);
+    CALLRUNOPS(aTHX);
     LEAVE;
     SPAGAIN;
     nret = SP - (PL_stack_base + oldmark);

perl.c

@@ -67,12 +67,6 @@ static I32 read_e_script(pTHX_ int idx, SV *buf_sv, int maxlen);
 #  define validate_suid(rsfp) S_validate_suid(aTHX_ rsfp)
 #endif
 
-#define CALL_BODY_SUB(myop) \
-    if (PL_op == (myop)) \
-        PL_op = PL_ppaddr[OP_ENTERSUB](aTHX); \
-    if (PL_op) \
-        CALLRUNOPS(aTHX);
-
 #define CALL_LIST_BODY(cv) \
     PUSHMARK(PL_stack_sp); \
     call_sv(MUTABLE_SV((cv)), G_EVAL|G_DISCARD|G_VOID);
@@ -3087,6 +3081,8 @@ Perl_call_sv(pTHX_ SV *sv, volatile I32 flags)
     if (!(flags & G_NOARGS))
         myop.op_flags |= OPf_STACKED;
     myop.op_flags |= OP_GIMME_REVERSE(flags);
+    myop.op_ppaddr = PL_ppaddr[OP_ENTERSUB];
+    myop.op_type = OP_ENTERSUB;
     SAVEOP();
     PL_op = (OP*)&myop;
 
@@ -3119,13 +3115,11 @@ Perl_call_sv(pTHX_ SV *sv, volatile I32 flags)
             method_op.op_ppaddr = PL_ppaddr[OP_METHOD];
             method_op.op_type = OP_METHOD;
         }
-        myop.op_ppaddr = PL_ppaddr[OP_ENTERSUB];
-        myop.op_type = OP_ENTERSUB;
     }
 
     if (!(flags & G_EVAL)) {
         CATCH_SET(TRUE);
-        CALL_BODY_SUB((OP*)&myop);
+        CALLRUNOPS(aTHX);
         retval = PL_stack_sp - (PL_stack_base + oldmark);
         CATCH_SET(oldcatch);
     }
@@ -3142,7 +3136,7 @@ Perl_call_sv(pTHX_ SV *sv, volatile I32 flags)
         switch (ret) {
         case 0:
  redo_body:
-            CALL_BODY_SUB((OP*)&myop);
+            CALLRUNOPS(aTHX);
             retval = PL_stack_sp - (PL_stack_base + oldmark);
             if (!(flags & G_KEEPERR)) {
                 CLEAR_ERRSV();