wrap op_sibling field access in OP_SIBLING* macros

Remove (almost all) direct access to the op_sibling field of OP structs,
and use these three new macros instead:

    OP_SIBLING(o);
    OP_HAS_SIBLING(o);
    OP_SIBLING_set(o, new_value);

OP_HAS_SIBLING is intended to be a slightly more efficient version of
OP_SIBLING when only boolean context is needed.

For now these three macros are just defined in the obvious way:

    #define OP_SIBLING(o)          (0 + (o)->op_sibling)
    #define OP_HAS_SIBLING(o)      (cBOOL((o)->op_sibling))
    #define OP_SIBLING_set(o, sib) ((o)->op_sibling = (sib))

but abstracting them out will allow us shortly to make the last pointer in
an op_sibling chain point back to the parent rather than being null, with
a new flag indicating whether this is the last op.

Perl_ck_fun() still has a couple of direct uses of op_sibling, since it
takes the field's address, which is not covered by these macros.

2 files changed, 10 insertions, 8 deletions

diff --git a/ext/arybase/arybase.pm b/ext/arybase/arybase.pm
index 3c090d66c2..67c71e7915 100644
--- a/ext/arybase/arybase.pm
+++ b/ext/arybase/arybase.pm
@@ -1,6 +1,6 @@
 package arybase;
 
-our $VERSION = "0.07";
+our $VERSION = "0.08";
 
 require XSLoader;
 XSLoader::load(); # This returns true, which makes require happy.
diff --git a/ext/arybase/arybase.xs b/ext/arybase/arybase.xs
index f8f9ce2b39..48358b564a 100644
--- a/ext/arybase/arybase.xs
+++ b/ext/arybase/arybase.xs
@@ -176,7 +176,7 @@ STATIC OP *ab_ck_sassign(pTHX_ OP *o) {
  o = (*ab_old_ck_sassign)(aTHX_ o);
  if (o->op_type == OP_SASSIGN && FEATURE_ARYBASE_IS_ENABLED) {
   OP *right = cBINOPx(o)->op_first;
-  OP *left = right->op_sibling;
+  OP *left = OP_SIBLING(right);
   if (left) ab_process_assignment(left, right);
  }
  return o;
@@ -186,8 +186,9 @@ STATIC OP *ab_ck_aassign(pTHX_ OP *o) {
  o = (*ab_old_ck_aassign)(aTHX_ o);
  if (o->op_type == OP_AASSIGN && FEATURE_ARYBASE_IS_ENABLED) {
   OP *right = cBINOPx(o)->op_first;
-  OP *left = cBINOPx(right->op_sibling)->op_first->op_sibling;
-  right = cBINOPx(right)->op_first->op_sibling;
+  OP *left = OP_SIBLING(right);
+  left = OP_SIBLING(cBINOPx(left)->op_first);
+  right = OP_SIBLING(cBINOPx(right)->op_first);
   ab_process_assignment(left, right);
  }
  return o;
@@ -375,10 +376,11 @@ static OP *ab_ck_base(pTHX_ OP *o)
    ab_map_store(o, o->op_ppaddr, base);
    o->op_ppaddr = new_pp;
    /* Break the aelemfast optimisation */
-   if (o->op_type == OP_AELEM &&
-       cBINOPo->op_first->op_sibling->op_type == OP_CONST) {
-     cBINOPo->op_first->op_sibling
-      = newUNOP(OP_NULL,0,cBINOPo->op_first->op_sibling);
+   if (o->op_type == OP_AELEM) {
+    OP *const first = cBINOPo->op_first;
+    if ( OP_SIBLING(first)->op_type == OP_CONST) {
+     OP_SIBLING_set(first, newUNOP(OP_NULL,0,OP_SIBLING(first)));
+    }
    }
   }
   else ab_map_delete(o);