re PR tree-optimization/82060 (ICE in refs_may_alias_p_1 with devirtualization enabled)

2017-09-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/82060
	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	Move devirtualization after stmt folding and before EH/AB/noreturn
	cleanup to get the stmt refs canonicalized.  Use a bool instead
	of gimple_modified_p since that doesn't work for NOPs.  Schedule
	NOPs generated by folding for removal.

	* g++.dg/torture/pr82060.C: New testcase.

From-SVN: r251650

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 238317e..85eab15 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2017-09-04  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/82060
+       * tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
+       Move devirtualization after stmt folding and before EH/AB/noreturn
+       cleanup to get the stmt refs canonicalized.  Use a bool instead
+       of gimple_modified_p since that doesn't work for NOPs.  Schedule
+       NOPs generated by folding for removal.
+
 2017-09-04  Richard Sandiford  <richard.sandiford@linaro.org>
            Alan Hayward  <alan.hayward@arm.com>
            David Sherwood  <david.sherwood@arm.com>

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 20b24b6..83f05b7 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-04  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/82060
+       * g++.dg/torture/pr82060.C: New testcase.
+
 2017-09-04  Alexander Monakov  <amonakov@ispras.ru>
 
        PR rtl-optimization/57448

diff --git a/gcc/testsuite/g++.dg/torture/pr82060.C b/gcc/testsuite/g++.dg/torture/pr82060.C
new file mode 100644 (file)
index 0000000..3cea930
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr82060.C
@@ -0,0 +1,32 @@
+// { dg-do compile }
+
+struct A
+{
+  char a[1]; // must be char array
+};
+
+struct B
+{
+  A& a() { return ma; } // must be accessed through a getter
+  A ma;
+};
+
+struct C
+{
+  B& b() { return mb; } // must be accessed through a getter
+  B mb;
+};
+
+struct D
+{
+  virtual A getA() = 0; // must be virtual
+};
+
+void
+foo(D& d) // The D object must not be created locally
+          // (so that getA implementation is not known at compile time?)
+{
+  C c;
+  for (;;) // must be in a loop
+    c.b().a() = d.getA();
+}

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 7243cf8..185c192 100644 (file)
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -4592,6 +4592,7 @@ eliminate_dom_walker::before_dom_children (basic_block b)
       /* If we didn't replace the whole stmt (or propagate the result
          into all uses), replace all uses on this stmt with their
         leaders.  */
+      bool modified = false;
       use_operand_p use_p;
       ssa_op_iter iter;
       FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
@@ -4613,7 +4614,7 @@ eliminate_dom_walker::before_dom_children (basic_block b)
                  || !bitmap_bit_p (inserted_exprs, SSA_NAME_VERSION (sprime))))
            {
              propagate_value (use_p, sprime);
-             gimple_set_modified (stmt, true);
+             modified = true;
              if (TREE_CODE (sprime) == SSA_NAME
                  && !is_gimple_debug (stmt))
                gimple_set_plf (SSA_NAME_DEF_STMT (sprime),
@@ -4621,8 +4622,56 @@ eliminate_dom_walker::before_dom_children (basic_block b)
            }
        }
 
+      /* Fold the stmt if modified, this canonicalizes MEM_REFs we propagated
+         into which is a requirement for the IPA devirt machinery.  */
+      gimple *old_stmt = stmt;
+      if (modified)
+       {
+         /* If a formerly non-invariant ADDR_EXPR is turned into an
+            invariant one it was on a separate stmt.  */
+         if (gimple_assign_single_p (stmt)
+             && TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR)
+           recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
+         gimple_stmt_iterator prev = gsi;
+         gsi_prev (&prev);
+         if (fold_stmt (&gsi))
+           {
+             /* fold_stmt may have created new stmts inbetween
+                the previous stmt and the folded stmt.  Mark
+                all defs created there as varying to not confuse
+                the SCCVN machinery as we're using that even during
+                elimination.  */
+             if (gsi_end_p (prev))
+               prev = gsi_start_bb (b);
+             else
+               gsi_next (&prev);
+             if (gsi_stmt (prev) != gsi_stmt (gsi))
+               do
+                 {
+                   tree def;
+                   ssa_op_iter dit;
+                   FOR_EACH_SSA_TREE_OPERAND (def, gsi_stmt (prev),
+                                              dit, SSA_OP_ALL_DEFS)
+                     /* As existing DEFs may move between stmts
+                        we have to guard VN_INFO_GET.  */
+                     if (! has_VN_INFO (def))
+                       VN_INFO_GET (def)->valnum = def;
+                   if (gsi_stmt (prev) == gsi_stmt (gsi))
+                     break;
+                   gsi_next (&prev);
+                 }
+               while (1);
+           }
+         stmt = gsi_stmt (gsi);
+         /* In case we folded the stmt away schedule the NOP for removal.  */
+         if (gimple_nop_p (stmt))
+           el_to_remove.safe_push (stmt);
+       }
+
       /* Visit indirect calls and turn them into direct calls if
-        possible using the devirtualization machinery.  */
+        possible using the devirtualization machinery.  Do this before
+        checking for required EH/abnormal/noreturn cleanup as devird
+        may expose more of those.  */
       if (gcall *call_stmt = dyn_cast <gcall *> (stmt))
        {
          tree fn = gimple_call_fn (call_stmt);
@@ -4631,24 +4680,21 @@ eliminate_dom_walker::before_dom_children (basic_block b)
              && virtual_method_call_p (fn))
            {
              tree otr_type = obj_type_ref_class (fn);
+             unsigned HOST_WIDE_INT otr_tok
+               = tree_to_uhwi (OBJ_TYPE_REF_TOKEN (fn));
              tree instance;
-             ipa_polymorphic_call_context context (current_function_decl, fn, stmt, &instance);
+             ipa_polymorphic_call_context context (current_function_decl,
+                                                   fn, stmt, &instance);
+             context.get_dynamic_type (instance, OBJ_TYPE_REF_OBJECT (fn),
+                                       otr_type, stmt);
              bool final;
-
-             context.get_dynamic_type (instance, OBJ_TYPE_REF_OBJECT (fn), otr_type, stmt);
-
-             vec <cgraph_node *>targets
+             vec <cgraph_node *> targets
                = possible_polymorphic_call_targets (obj_type_ref_class (fn),
-                                                    tree_to_uhwi
-                                                      (OBJ_TYPE_REF_TOKEN (fn)),
-                                                    context,
-                                                    &final);
+                                                    otr_tok, context, &final);
              if (dump_file)
                dump_possible_polymorphic_call_targets (dump_file, 
                                                        obj_type_ref_class (fn),
-                                                       tree_to_uhwi
-                                                         (OBJ_TYPE_REF_TOKEN (fn)),
-                                                       context);
+                                                       otr_tok, context);
              if (final && targets.length () <= 1 && dbg_cnt (devirt))
                {
                  tree fn;
@@ -4658,7 +4704,7 @@ eliminate_dom_walker::before_dom_children (basic_block b)
                    fn = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
                  if (dump_enabled_p ())
                    {
-                     location_t loc = gimple_location_safe (stmt);
+                     location_t loc = gimple_location (stmt);
                      dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, loc,
                                       "converting indirect call to "
                                       "function %s\n",
@@ -4675,50 +4721,13 @@ eliminate_dom_walker::before_dom_children (basic_block b)
                          == void_type_node))
                    gimple_call_set_fntype (call_stmt, TREE_TYPE (fn));
                  maybe_remove_unused_call_args (cfun, call_stmt);
-                 gimple_set_modified (stmt, true);
+                 modified = true;
                }
            }
        }
 
-      if (gimple_modified_p (stmt))
+      if (modified)
        {
-         /* If a formerly non-invariant ADDR_EXPR is turned into an
-            invariant one it was on a separate stmt.  */
-         if (gimple_assign_single_p (stmt)
-             && TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR)
-           recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
-         gimple *old_stmt = stmt;
-         gimple_stmt_iterator prev = gsi;
-         gsi_prev (&prev);
-         if (fold_stmt (&gsi))
-           {
-             /* fold_stmt may have created new stmts inbetween
-                the previous stmt and the folded stmt.  Mark
-                all defs created there as varying to not confuse
-                the SCCVN machinery as we're using that even during
-                elimination.  */
-             if (gsi_end_p (prev))
-               prev = gsi_start_bb (b);
-             else
-               gsi_next (&prev);
-             if (gsi_stmt (prev) != gsi_stmt (gsi))
-               do
-                 {
-                   tree def;
-                   ssa_op_iter dit;
-                   FOR_EACH_SSA_TREE_OPERAND (def, gsi_stmt (prev),
-                                              dit, SSA_OP_ALL_DEFS)
-                     /* As existing DEFs may move between stmts
-                        we have to guard VN_INFO_GET.  */
-                     if (! has_VN_INFO (def))
-                       VN_INFO_GET (def)->valnum = def;
-                   if (gsi_stmt (prev) == gsi_stmt (gsi))
-                     break;
-                   gsi_next (&prev);
-                 }
-               while (1);
-           }
-         stmt = gsi_stmt (gsi);
          /* When changing a call into a noreturn call, cfg cleanup
             is needed to fix up the noreturn call.  */
          if (!was_noreturn