Perl_more_bodies - figure out sizing from sv_type

`Perl_more_bodies` allocates and sets up a new arena for the likes of
SV body, HE, and HVAUX structs. It has traditionally been called with
three arguments:
  * the `svtype`
  * the size of the structs that the arena will contain
  * the size of the arena to allocate

This commit changes the function definition such that it only takes
a single argument: the `svtype`. From that, and with a bit of
additional logic to account of HE and HVAUX using the indexes
notionally for SVt_NULL and SVt_IV, `Perl_more_bodies` can figure
out the sizing for itself.

The rationale for this is that:
  * When an application is starting up, the need to call `Perl_more_bodies`
    is the unlikely case in each new SV allocation or upgrade.
  * When the application has reached a steady state, the function
    may not be called regardless of how many SVs are created or upgraded.

With `Perl_newSV_type` being an inline function, there are a lot of
potential callers to this function though, each of which will have
two `mov` instructions for pushing the two size parameters onto the
stack should the need to call `Perl_more_bodies` arise. Removing two
instructions from each potential call site should help reduce binary
size a little and avoid taking up unnecessary space in the CPU's
instruction buffer.

Author: richardleach

embed.fnc

@@ -2024,9 +2024,7 @@ p	|int	|mode_from_discipline					\
 				|STRLEN len
 
 : Used in sv.c and hv.c
-Cop	|void * |more_bodies	|const svtype sv_type			\
-				|const size_t body_size 		\
-				|const size_t arena_size
+Cop	|void * |more_bodies	|const svtype sv_type
 Cp	|const char *|moreswitches					\
 				|NN const char *s
 Adp	|void	|mortal_destructor_sv					\

hv.c

@@ -159,7 +159,7 @@ S_new_he(pTHX)
     void ** const root = &PL_body_roots[HE_ARENA_ROOT_IX];
 
     if (!*root)
-        Perl_more_bodies(aTHX_ HE_ARENA_ROOT_IX, sizeof(HE), PERL_ARENA_SIZE);
+        Perl_more_bodies(aTHX_ HE_ARENA_ROOT_IX);
     he = (HE*) *root;
     assert(he);
     *root = HeNEXT(he);

proto.h

@@ -856,10 +856,22 @@ available in hv.c. Similarly SVt_IV is re-used for HVAUX_ARENA_ROOT_IX.
 
 
 void *
-Perl_more_bodies (pTHX_ const svtype sv_type, const size_t body_size,
-                  const size_t arena_size)
+Perl_more_bodies (pTHX_ const svtype sv_type)
 {
     void ** const root = &PL_body_roots[sv_type];
+
+    const struct body_details *type_details =
+        (sv_type > SVt_IV)
+            ? bodies_by_type + sv_type
+            : (sv_type == SVt_NULL)
+                ? NULL
+                : &fake_hv_with_aux
+                ;
+
+    const size_t body_size = (type_details) ? type_details->body_size
+                                            : sizeof(HE);
+    const size_t arena_size = (type_details) ? type_details->arena_size
+                                             : PERL_ARENA_SIZE;
     struct arena_desc *adesc;
     struct arena_set *aroot = (struct arena_set *) PL_body_arenas;
     unsigned int curr;
@@ -1291,7 +1303,7 @@ Perl_hv_auxalloc(pTHX_ HV *hv) {
 #ifdef PURIFY
     new_body = new_NOARENAZ(&fake_hv_with_aux);
 #else
-    new_body_from_arena(new_body, HVAUX_ARENA_ROOT_IX, fake_hv_with_aux);
+    new_body_from_arena(new_body, HVAUX_ARENA_ROOT_IX);
 #endif
 
     old_body = SvANY(hv);
@@ -14713,7 +14725,7 @@ S_sv_dup_common(pTHX_ const SV *const ssv, CLONE_PARAMS *const param)
 #ifdef PURIFY
                     new_body = new_NOARENA(sv_type_details);
 #else
-                    new_body_from_arena(new_body, HVAUX_ARENA_ROOT_IX, fake_hv_with_aux);
+                    new_body_from_arena(new_body, HVAUX_ARENA_ROOT_IX);
 #endif
                     goto have_body;
                 }

sv.c

@@ -180,6 +180,14 @@ ALIGNED_TYPE(XPVOBJ);
         STRUCT_OFFSET(type, last_member) \
         + sizeof (((type*)SvANY((const SV *)0))->last_member)
 
+static const struct body_details fake_hv_with_aux =
+    /* The SVt_IV arena is used for (larger) PVHV bodies.  */
+    { sizeof(ALIGNED_TYPE_NAME(XPVHV_WITH_AUX)),
+      copy_length(XPVHV, xhv_max),
+      0,
+      SVt_PVHV, TRUE, NONV, HASARENA,
+      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVHV_WITH_AUX))) };
+
 static const struct body_details bodies_by_type[] = {
     /* HEs use this offset for their arena.  */
     { 0, 0, 0, SVt_NULL, FALSE, NONV, NOARENA, 0 },
@@ -328,21 +336,19 @@ static const struct body_details bodies_by_type[] = {
 #ifndef PURIFY
 
 /* grab a new thing from the arena's free list, allocating more if necessary. */
-#define new_body_from_arena(xpv, root_index, type_meta) \
+#define new_body_from_arena(xpv, root_index) \
     STMT_START { \
         void ** const r3wt = &PL_body_roots[root_index]; \
         xpv = (PTR_TBL_ENT_t*) (*((void **)(r3wt))      \
-          ? *((void **)(r3wt)) : Perl_more_bodies(aTHX_ root_index, \
-                                             type_meta.body_size,\
-                                             type_meta.arena_size)); \
+          ? *((void **)(r3wt)) : Perl_more_bodies(aTHX_ root_index)); \
         *(r3wt) = *(void**)(xpv); \
     } STMT_END
 
 PERL_STATIC_INLINE void *
 S_new_body(pTHX_ const svtype sv_type)
 {
     void *xpv;
-    new_body_from_arena(xpv, sv_type, bodies_by_type[sv_type]);
+    new_body_from_arena(xpv, sv_type);
     return xpv;
 }
 
@@ -351,14 +357,6 @@ S_new_body(pTHX_ const svtype sv_type)
 static const struct body_details fake_rv =
     { 0, 0, 0, SVt_IV, FALSE, NONV, NOARENA, 0 };
 
-static const struct body_details fake_hv_with_aux =
-    /* The SVt_IV arena is used for (larger) PVHV bodies.  */
-    { sizeof(ALIGNED_TYPE_NAME(XPVHV_WITH_AUX)),
-      copy_length(XPVHV, xhv_max),
-      0,
-      SVt_PVHV, TRUE, NONV, HASARENA,
-      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVHV_WITH_AUX))) };
-
 /*
 =for apidoc newSV_type