[Bug middle-end/28071] [4.1 regression] A file that can not be compiled in reasonable time/space

[zaks at il dot ibm dot com]

------- Comment #56 from zaks at il dot ibm dot com  2007-01-15 07:19 -------
(In reply to comment #55)
> Created an attachment (id=12879)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12879&action=view) [edit]
> Patch for scheduler dependency lists.

Looks like a pretty good cleanup IMHO. Here are some comments.

o dep_def: representing a dependence edge including both producer and consumer
is very handy, albeit somewhat redundant as we're usually traversing all cons
connected to a pro or vice versa. (I.e., has its pros and cons, but mostly pros
I agree - also done in ddg.h/ddg_edge.) Maybe comment why both 'kind' and 'ds'
are needed, as one supersedes the other.

o dep_node_def: this is a node in a (doubly-linked) chain, but it represents an
*edge* in terms of the data-dependence graph. The prev_nextp field is a "/*
Pointer to the next field of the previous node in the list.  */" except for the
first node on the list, whose prev_nextp points to itself, right?

o dep_data_node_def: holding the two conjugate dependence edges together is
very useful when switching directions. But perhaps most of the accesses go in
one direction (e.g. iterating over cons of a pro), and having both conjugates
structed together may reduce cache efficiency. So you may consider connecting
each dep_node_def to its conjugate, not necessarily forcing them to be placed
adjacent in memory.

o To add to the checking routines, the following can be checked: every
dep_node_def is pointed-to by either its data->back xor its data->forw, right?
If so, this can be used to identify if a dep_node_def is forward or backward;
that all nodes on a list are forward (and share the same pro) or backward (and
share the same con); and to assert the following regarding L:
+/* Add a dependency described by DEP to the list L.
+   L should be either INSN_DEPS1 or RESOLVED_DEPS1.  */

o insn_cost (insn, dep): maybe it's better to break this into insn_cost (insn)
of a producer regardless of consumers, and "dep_cost (dep)".

o The comment explaining what 'resolve_dep' does can be inlined together with
its code. 

+/* Detach dep_node N from the list.  */
+static void
+dep_node_detach (dep_node_t n)
+{
+  dep_node_t *prev_nextp = DEP_NODE_PREV_NEXTP (n);
+  dep_node_t next = DEP_NODE_NEXT (n);
+
+  *prev_nextp = next;
+
+  if (next != NULL)
+    DEP_NODE_PREV_NEXTP (next) = prev_nextp;
maybe complete the detachment by adding:
DEP_NODE_PREV_NEXTP (n) = NULL;
DEP_NODE_NEXT (n) = NULL;
+}


+/* Attach NEXT to the next field pointed to by PREV_NEXTP.  */
^^^^^^^^^^^N to appear after node X whose &DEP_NODE_NEXT (X) is given by 
PREV_NEXT_P
+static void
+dep_node_attach (dep_node_t n, dep_node_t *prev_nextp)


better place
+dep_node_check_p (dep_node_t n)
next to
+dep_nodes_check_p (dep_node_t n)


+/* Make a copy of FROM in TO with substitutin consumer with CON.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^substituting consumer with CON.

Ayal.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28071