Limit AA walking in IPA summary generation

2019-01-20  Martin Jambor  <mjambor@suse.cz>

	PR ipa/87615
	* ipa-prop.h (struct ipa_func_body_info): Replaced field aa_walked
	with aa_walk_budget.
	* cgraph.h (ipa_polymorphic_call_context::get_dynamic_type): Add
	aa_walk_budget_p parameter.
	* ipa-fnsummary.c (unmodified_parm_1): New parameter fbi.  Limit AA
	walk.  Updated all callers.
	(unmodified_parm): New parameter fbi, pass it to unmodified_parm_1.
	(eliminated_by_inlining_prob): New parameter fbi, pass it on to
	unmodified_parm.
	(will_be_nonconstant_expr_predicate): New parameter fbi, removed
	parameter info.  Extract info from fbi.  Pass fbi to recursive calls
	and to unmodified_parm.
	(phi_result_unknown_predicate): New parameter fbi, removed parameter
	info, updated call to will_be_nonconstant_expr_predicate.
	(param_change_prob): New parameter fbi, limit AA walking.
	(analyze_function_body): Initialize aa_walk_budget in fbi.  Update
	calls to various above functions.
	* ipa-polymorphic-call.c (get_dynamic_type): Add aa_walk_budget_p
	parameter.  Use it to limit AA walking.
	* ipa-prop.c (detect_type_change_from_memory_writes): New parameter
	fbi, limit AA walk.
	(detect_type_change): New parameter fbi, pass it on to
	detect_type_change_from_memory_writes.
	(detect_type_change_ssa): Likewise.
	(aa_overwalked): Removed.
	(parm_preserved_before_stmt_p): Assume fbi is never NULL, stream line
	accordingly, adjust to the neew AA limiting scheme.
	(parm_ref_data_preserved_p): Likewise.
	(ipa_compute_jump_functions_for_edge): Adjust call to
	get_dynamic_type.
	(ipa_analyze_call_uses): Likewise.
	(ipa_analyze_virtual_call_uses): Pass fbi to detect_type_change_ssa.
	(ipa_analyze_node): Initialize aa_walk_budget.
	(ipcp_transform_function): Likewise.
	* tree-ssa-sccvn.c (eliminate_dom_walker::eliminate_stmt): Update call
	to get_dynamic_type.

From-SVN: r268107

1 files changed, 24 insertions, 4 deletions

diff --git a/gcc/ipa-polymorphic-call.c b/gcc/ipa-polymorphic-call.c
index b93bf55..75d8ebc 100644
--- a/gcc/ipa-polymorphic-call.c
+++ b/gcc/ipa-polymorphic-call.c
@@ -1554,13 +1554,18 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data)
 
    We do not include this analysis in the context analysis itself, because
    it needs memory SSA to be fully built and the walk may be expensive.
-   So it is not suitable for use withing fold_stmt and similar uses.  */
+   So it is not suitable for use withing fold_stmt and similar uses.
+
+   AA_WALK_BUDGET_P, if not NULL, is how statements we should allow
+   walk_aliased_vdefs to examine.  The value should be decremented by the
+   number of stetements we examined or set to zero if exhausted.  */
 
 bool
 ipa_polymorphic_call_context::get_dynamic_type (tree instance,
 						tree otr_object,
 						tree otr_type,
-						gimple *call)
+						gimple *call,
+						unsigned *aa_walk_budget_p)
 {
   struct type_change_info tci;
   ao_ref ao;
@@ -1723,8 +1728,13 @@ ipa_polymorphic_call_context::get_dynamic_type (tree instance,
   tci.speculative = 0;
   tci.seen_unanalyzed_store = false;
 
-  walk_aliased_vdefs (&ao, gimple_vuse (stmt), check_stmt_for_type_change,
-		      &tci, NULL, &function_entry_reached);
+  unsigned aa_walk_budget = 0;
+  if (aa_walk_budget_p)
+    aa_walk_budget = *aa_walk_budget_p + 1;
+
+  int walked
+   = walk_aliased_vdefs (&ao, gimple_vuse (stmt), check_stmt_for_type_change,
+			 &tci, NULL, &function_entry_reached, aa_walk_budget);
 
   /* If we did not find any type changing statements, we may still drop
      maybe_in_construction flag if the context already have outer type. 
@@ -1772,6 +1782,16 @@ ipa_polymorphic_call_context::get_dynamic_type (tree instance,
      only if there was dyanmic type store that may affect given variable
      (seen_unanalyzed_store)  */
 
+  if (walked < 0)
+    {
+      if (dump_file)
+	fprintf (dump_file, "  AA walk budget exhausted.\n");
+      *aa_walk_budget_p = 0;
+      return false;
+    }
+  else if (aa_walk_budget_p)
+    *aa_walk_budget_p -= walked;
+
   if (!tci.type_maybe_changed
       || (outer_type
 	  && !dynamic