+#else /* !defined(PL_OP_SLAB_ALLOC) */
+
+/* See the explanatory comments above struct opslab in op.h. */
+
+# ifndef PERL_SLAB_SIZE
+# define PERL_SLAB_SIZE 64
+# endif
+# ifndef PERL_MAX_SLAB_SIZE
+# define PERL_MAX_SLAB_SIZE 2048
+# endif
+
+/* rounds up to nearest pointer */
+# define SIZE_TO_PSIZE(x) (((x) + sizeof(I32 *) - 1)/sizeof(I32 *))
+# define DIFF(o,p) ((size_t)((I32 **)(p) - (I32**)(o)))
+
+static OPSLAB *
+S_new_slab(pTHX_ size_t sz)
+{
+ OPSLAB *slab = (OPSLAB *)PerlMemShared_calloc(sz, sizeof(I32 *));
+ slab->opslab_first = (OPSLOT *)((I32 **)slab + sz - 1);
+ return slab;
+}
+
+/* requires double parens and aTHX_ */
+#define DEBUG_S_warn(args) \
+ DEBUG_S( \
+ PerlIO_printf(Perl_debug_log, "%s", SvPVx_nolen(Perl_mess args)) \
+ )
+
+void *
+Perl_Slab_Alloc(pTHX_ size_t sz)
+{
+ dVAR;
+ OPSLAB *slab;
+ OPSLAB *slab2;
+ OPSLOT *slot;
+ OP *o;
+ size_t opsz, space;
+
+ if (!PL_compcv || CvROOT(PL_compcv)
+ || (CvSTART(PL_compcv) && !CvSLABBED(PL_compcv)))
+ return PerlMemShared_calloc(1, sz);
+
+ if (!CvSTART(PL_compcv)) { /* sneak it in here */
+ CvSTART(PL_compcv) =
+ (OP *)(slab = S_new_slab(aTHX_ PERL_SLAB_SIZE));
+ CvSLABBED_on(PL_compcv);
+ slab->opslab_refcnt = 2; /* one for the CV; one for the new OP */
+ }
+ else ++(slab = (OPSLAB *)CvSTART(PL_compcv))->opslab_refcnt;
+
+ opsz = SIZE_TO_PSIZE(sz);
+ sz = opsz + OPSLOT_HEADER_P;
+
+ if (slab->opslab_freed) {
+ OP **too = &slab->opslab_freed;
+ o = *too;
+ DEBUG_S_warn((aTHX_ "found free op at %p, slab %p", o, slab));
+ while (o && DIFF(OpSLOT(o), OpSLOT(o)->opslot_next) < sz) {
+ DEBUG_S_warn((aTHX_ "Alas! too small"));
+ o = *(too = &o->op_next);
+ if (o) { DEBUG_S_warn((aTHX_ "found another free op at %p", o)); }
+ }
+ if (o) {
+ *too = o->op_next;
+ Zero(o, opsz, I32 *);
+ o->op_slabbed = 1;
+ return (void *)o;
+ }
+ }
+
+# define INIT_OPSLOT \
+ slot->opslot_slab = slab; \
+ slot->opslot_next = slab2->opslab_first; \
+ slab2->opslab_first = slot; \
+ o = &slot->opslot_op; \
+ o->op_slabbed = 1
+
+ /* The partially-filled slab is next in the chain. */
+ slab2 = slab->opslab_next ? slab->opslab_next : slab;
+ if ((space = DIFF(&slab2->opslab_slots, slab2->opslab_first)) < sz) {
+ /* Remaining space is too small. */
+
+ /* If we can fit a BASEOP, add it to the free chain, so as not
+ to waste it. */
+ if (space >= SIZE_TO_PSIZE(sizeof(OP)) + OPSLOT_HEADER_P) {
+ slot = &slab2->opslab_slots;
+ INIT_OPSLOT;
+ o->op_type = OP_FREED;
+ o->op_next = slab->opslab_freed;
+ slab->opslab_freed = o;
+ }
+
+ /* Create a new slab. Make this one twice as big. */
+ slot = slab2->opslab_first;
+ while (slot->opslot_next) slot = slot->opslot_next;
+ slab2 = S_new_slab(aTHX_ DIFF(slab2, slot)*2 > PERL_MAX_SLAB_SIZE
+ ? PERL_MAX_SLAB_SIZE
+ : DIFF(slab2, slot)*2);
+ slab2->opslab_next = slab->opslab_next;
+ slab->opslab_next = slab2;
+ }
+ assert(DIFF(&slab2->opslab_slots, slab2->opslab_first) >= sz);
+
+ /* Create a new op slot */
+ slot = (OPSLOT *)((I32 **)slab2->opslab_first - sz);
+ assert(slot >= &slab2->opslab_slots);
+ if (DIFF(&slab2->opslab_slots, slot)
+ < SIZE_TO_PSIZE(sizeof(OP)) + OPSLOT_HEADER_P)
+ slot = &slab2->opslab_slots;
+ INIT_OPSLOT;
+ DEBUG_S_warn((aTHX_ "allocating op at %p, slab %p", o, slab));
+ return (void *)o;
+}
+
+# undef INIT_OPSLOT
+
+/* This cannot possibly be right, but it was copied from the old slab
+ allocator, to which it was originally added, without explanation, in
+ commit 083fcd5. */
+# ifdef NETWARE
+# define PerlMemShared PerlMem
+# endif
+
+void
+Perl_Slab_Free(pTHX_ void *op)
+{
+ dVAR;
+ OP * const o = (OP *)op;
+ OPSLAB *slab;
+
+ PERL_ARGS_ASSERT_SLAB_FREE;
+
+ if (!o->op_slabbed) {
+ PerlMemShared_free(op);
+ return;
+ }
+
+ slab = OpSLAB(o);
+ /* If this op is already freed, our refcount will get screwy. */
+ assert(o->op_type != OP_FREED);
+ o->op_type = OP_FREED;
+ o->op_next = slab->opslab_freed;
+ slab->opslab_freed = o;
+ DEBUG_S_warn((aTHX_ "free op at %p, recorded in slab %p", o, slab));
+ OpslabREFCNT_dec_padok(slab);
+}
+
+void
+Perl_opslab_free_nopad(pTHX_ OPSLAB *slab)
+{
+ dVAR;
+ const bool havepad = !!PL_comppad;
+ PERL_ARGS_ASSERT_OPSLAB_FREE_NOPAD;
+ if (havepad) {
+ ENTER;
+ PAD_SAVE_SETNULLPAD();
+ }
+ opslab_free(slab);
+ if (havepad) LEAVE;
+}
+
+void
+Perl_opslab_free(pTHX_ OPSLAB *slab)
+{
+ dVAR;
+ OPSLAB *slab2;
+ PERL_ARGS_ASSERT_OPSLAB_FREE;
+ DEBUG_S_warn((aTHX_ "freeing slab %p", slab));
+ assert(slab->opslab_refcnt == 1);
+ for (; slab; slab = slab2) {
+ slab2 = slab->opslab_next;
+# ifdef DEBUGGING
+ slab->opslab_refcnt = ~(size_t)0;
+# endif
+ PerlMemShared_free(slab);
+ }
+}
+
+void
+Perl_opslab_force_free(pTHX_ OPSLAB *slab)
+{
+ OPSLAB *slab2;
+ OPSLOT *slot;
+# ifdef DEBUGGING
+ size_t savestack_count = 0;
+# endif
+ PERL_ARGS_ASSERT_OPSLAB_FORCE_FREE;
+ slab2 = slab;
+ do {
+ for (slot = slab2->opslab_first;
+ slot->opslot_next;
+ slot = slot->opslot_next) {
+ if (slot->opslot_op.op_type != OP_FREED
+ && !(slot->opslot_op.op_savefree
+# ifdef DEBUGGING
+ && ++savestack_count
+# endif
+ )
+ ) {
+ assert(slot->opslot_op.op_slabbed);
+ slab->opslab_refcnt++; /* op_free may free slab */
+ op_free(&slot->opslot_op);
+ if (!--slab->opslab_refcnt) goto free;
+ }
+ }
+ } while ((slab2 = slab2->opslab_next));
+ /* > 1 because the CV still holds a reference count. */
+ if (slab->opslab_refcnt > 1) { /* still referenced by the savestack */
+# ifdef DEBUGGING
+ assert(savestack_count == slab->opslab_refcnt-1);
+# endif
+ return;
+ }
+ free:
+ opslab_free(slab);
+}
+