py/parse: Optimise away parse node that's just parenthesis around expr.
Before this patch, (x+y)*z would be parsed to a tree that contained a
redundant identity parse node corresponding to the parenthesis. With
this patch such nodes are optimised away, which reduces memory
requirements for expressions with parenthesis, and simplifies the
compiler because it doesn't need to handle this identity case.
A parenthesis parse node is still needed for tuples.
diff --git a/py/compile.c b/py/compile.c
index f349dca..8a30518 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -299,14 +299,12 @@
if (jump_if == false) {
EMIT_ARG(jump, label);
}
- } else if (MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp)) {
+ } else {
+ assert(MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp));
// non-empty tuple, acts as true for the condition
if (jump_if == true) {
EMIT_ARG(jump, label);
}
- } else {
- // parenthesis around 1 item, is just that item
- c_if_cond(comp, pns->nodes[0], jump_if, label);
}
return;
}
@@ -420,7 +418,6 @@
// assigns top of stack to pn
STATIC void c_assign(compiler_t *comp, mp_parse_node_t pn, assign_kind_t assign_kind) {
- tail_recursion:
assert(!MP_PARSE_NODE_IS_NULL(pn));
if (MP_PARSE_NODE_IS_LEAF(pn)) {
if (MP_PARSE_NODE_IS_ID(pn)) {
@@ -462,16 +459,13 @@
if (MP_PARSE_NODE_IS_NULL(pns->nodes[0])) {
// empty tuple
goto cannot_assign;
- } else if (MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp)) {
+ } else {
+ assert(MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp));
if (assign_kind != ASSIGN_STORE) {
goto bad_aug;
}
pns = (mp_parse_node_struct_t*)pns->nodes[0];
goto testlist_comp;
- } else {
- // parenthesis around 1 item, is just that item
- pn = pns->nodes[0];
- goto tail_recursion;
}
break;
@@ -885,7 +879,10 @@
}
} else if (MP_PARSE_NODE_IS_STRUCT_KIND(pn, PN_atom_paren)) {
pn = ((mp_parse_node_struct_t*)pn)->nodes[0];
- if (MP_PARSE_NODE_IS_STRUCT_KIND(pn, PN_testlist_comp)) {
+ if (MP_PARSE_NODE_IS_NULL(pn)) {
+ goto cannot_delete;
+ } else {
+ assert(MP_PARSE_NODE_IS_STRUCT_KIND(pn, PN_testlist_comp));
mp_parse_node_struct_t *pns = (mp_parse_node_struct_t*)pn;
// TODO perhaps factorise testlist_comp code with other uses of PN_testlist_comp
@@ -915,12 +912,9 @@
c_del_stmt(comp, pns->nodes[0]);
c_del_stmt(comp, pns->nodes[1]);
}
- } else {
- // tuple with 1 element
- c_del_stmt(comp, pn);
}
} else {
- // TODO is there anything else to implement?
+ // some arbitrary statment that we can't delete (eg del 1)
goto cannot_delete;
}
@@ -2185,7 +2179,8 @@
if (MP_PARSE_NODE_IS_NULL(pns->nodes[0])) {
// an empty tuple
c_tuple(comp, MP_PARSE_NODE_NULL, NULL);
- } else if (MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp)) {
+ } else {
+ assert(MP_PARSE_NODE_IS_STRUCT_KIND(pns->nodes[0], PN_testlist_comp));
pns = (mp_parse_node_struct_t*)pns->nodes[0];
assert(!MP_PARSE_NODE_IS_NULL(pns->nodes[1]));
if (MP_PARSE_NODE_IS_STRUCT(pns->nodes[1])) {
@@ -2209,9 +2204,6 @@
tuple_with_2_items:
c_tuple(comp, MP_PARSE_NODE_NULL, pns);
}
- } else {
- // parenthesis around a single item, is just that item
- compile_node(comp, pns->nodes[0]);
}
}