[Bug tree-optimization/51600] [4.7 Regression] ice in estimate_local_effects

["hubicka at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51600

--- Comment #6 from Jan Hubicka <hubicka at gcc dot gnu.org> 2012-01-04 14:57:34 UTC ---
Estimate_edge_devirt_benefit seems to not make much of sense in mixing the
effects of inlining into the local size. Unforutnately we don't really have
much infrastructure for similar cases. For 4.8 I plan to add benefit metrics
that allows inline-analysis to hint inliner that the inlining is cool idea
besides the local code size/time improvements.

I am testing the following patch.

Index: ipa-inline-analysis.c
===================================================================
--- ipa-inline-analysis.c       (revision 182871)
+++ ipa-inline-analysis.c       (working copy)
@@ -2204,9 +2204,9 @@ estimate_edge_devirt_benefit (struct cgr
   tree target;
   struct cgraph_node *callee;
   struct inline_summary *isummary;
-  int edge_size = 0, edge_time = 0;
+  int edge_size, edge_time, time_diff, size_diff;

-  if (!known_vals || !known_binfos)
+  if (!known_vals && !known_binfos)
     return;

   target = ipa_get_indirect_edge_target (ie, known_vals, known_binfos);
@@ -2214,10 +2214,12 @@ estimate_edge_devirt_benefit (struct cgr
     return;

   /* Account for difference in cost between indirect and direct calls.  */
-  *size -= ((eni_size_weights.indirect_call_cost - eni_size_weights.call_cost)
-           * INLINE_SIZE_SCALE);
-  *time -= ((eni_time_weights.indirect_call_cost - eni_time_weights.call_cost)
-           * INLINE_TIME_SCALE * prob / REG_BR_PROB_BASE);
+  size_diff = ((eni_size_weights.indirect_call_cost -
eni_size_weights.call_cost)
+               * INLINE_SIZE_SCALE);
+  *size -= size_diff;
+  time_diff = ((eni_time_weights.indirect_call_cost -
eni_time_weights.call_cost)
+              * INLINE_TIME_SCALE * prob / REG_BR_PROB_BASE);
+  *time -= time_diff;

   callee = cgraph_get_node (target);
   if (!callee || !callee->analyzed)
@@ -2229,21 +2231,18 @@ estimate_edge_devirt_benefit (struct cgr
   estimate_edge_size_and_time (ie, &edge_size, &edge_time, prob);

   /* Count benefit only from functions that definitely will be inlined
-     if additional context from NODE's caller were available.  */
-  if (edge_size >= isummary->size * INLINE_SIZE_SCALE)
+     if additional context from NODE's caller were available. 
+
+     We just account overall size change by inlining.  TODO:
+     we really need to add sort of benefit metrics for these kind of
+     cases. */
+  if (edge_size - size_diff >= isummary->size * INLINE_SIZE_SCALE)
     {
       /* Subtract size and time that we added for edge IE.  */
-      *size -= edge_size;
-      *time -= edge_time;
+      *size -= edge_size - size_diff;

-      /* Subtract benefit from inlining devirtualized call.  */
-      *size -= edge_size - isummary->size * INLINE_SIZE_SCALE;
-      *time -= edge_time - (isummary->time * INLINE_TIME_SCALE * prob
-                           / REG_BR_PROB_BASE);
-
-      /* TODO: estimate benefit from optimizing CALLEE's body provided
-        additional context from IE call site.
-        For insipiration see ipa-cp.c: devirtualization_time_bonus().  */
+      /* Account inlined call.  */
+      *size += isummary->size * INLINE_SIZE_SCALE;
     }
 }