[PATCH] Fix devirtualization ICE (PR tree-optimization/59622, take 3)

Jakub Jelinek jakub@redhat.com
Wed Jan 8 22:45:00 GMT 2014


On Wed, Jan 08, 2014 at 12:19:02PM +0100, Richard Biener wrote:
> On Wed, 8 Jan 2014, Jakub Jelinek wrote:
> 
> > On Wed, Jan 08, 2014 at 12:15:40PM +0100, Richard Biener wrote:
> > > > I start to think this is a too complex transform for stmt folding ...
> > > 
> > > Alternatively do update_call_from_tree (gsi, get_or_create_ssa_default_def 
> > > (cfun, create_tmp_var (TREE_TYPE (lhs)))).
> > 
> > The lhs might not be is_gimple_reg_type though.  What to do in that case?
> 
> In that case you can remove the stmt.

Ok, so like this?  Unfortunately, I haven't been able to construct a
testcase where this would be folded later than during gimplification where
lhs is obviously not a SSA_NAME and we can safely replace the call.

Bootstrapped/regtested on x86_64-linux and i686-linux.

2014-01-08  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/59622
	* gimple-fold.c (gimple_fold_call): Fix a typo in message.  Handle
	__cxa_pure_virtual similarly to __builtin_unreachable, but replace
	the OBJ_TYPE_REF call with the noreturn and add if needed a setter
	of the lhs SSA_NAME.  Don't devirtualize for inplace at all.

	* g++.dg/opt/pr59622-2.C: New test.
	* g++.dg/opt/pr59622-3.C: New test.
	* g++.dg/opt/pr59622-4.C: New test.

--- gcc/gimple-fold.c.jj	2014-01-08 10:23:24.536443566 +0100
+++ gcc/gimple-fold.c	2014-01-08 17:02:40.356635177 +0100
@@ -1167,7 +1167,7 @@ gimple_fold_call (gimple_stmt_iterator *
                                                  (OBJ_TYPE_REF_EXPR (callee)))))
 	    {
 	      fprintf (dump_file,
-		       "Type inheritnace inconsistent devirtualization of ");
+		       "Type inheritance inconsistent devirtualization of ");
 	      print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
 	      fprintf (dump_file, " to ");
 	      print_generic_expr (dump_file, callee, TDF_SLIM);
@@ -1177,26 +1177,46 @@ gimple_fold_call (gimple_stmt_iterator *
 	  gimple_call_set_fn (stmt, OBJ_TYPE_REF_EXPR (callee));
 	  changed = true;
 	}
-      else if (flag_devirtualize && virtual_method_call_p (callee))
+      else if (flag_devirtualize && !inplace && virtual_method_call_p (callee))
 	{
 	  bool final;
 	  vec <cgraph_node *>targets
 	    = possible_polymorphic_call_targets (callee, &final);
 	  if (final && targets.length () <= 1)
 	    {
+	      tree fndecl;
 	      if (targets.length () == 1)
+		fndecl = targets[0]->decl;
+	      else
+		fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+
+	      /* If fndecl (like __builtin_unreachable or
+		 __cxa_pure_virtual) takes no arguments, doesn't have
+		 return value and is noreturn, if the call doesn't have
+		 lhs or lhs isn't SSA_NAME, replace the call with
+		 the noreturn call, otherwise insert it before the call
+		 and replace the call with setting of lhs to default def.  */
+	      if (TREE_THIS_VOLATILE (fndecl)
+		  && VOID_TYPE_P (TREE_TYPE (TREE_TYPE (fndecl)))
+		  && TYPE_ARG_TYPES (TREE_TYPE (fndecl)) == void_list_node)
 		{
-		  gimple_call_set_fndecl (stmt, targets[0]->decl);
-		  changed = true;
-		}
-	      else if (!inplace)
-		{
-		  tree fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+		  tree lhs = gimple_call_lhs (stmt);
 		  gimple new_stmt = gimple_build_call (fndecl, 0);
 		  gimple_set_location (new_stmt, gimple_location (stmt));
-		  gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
+		  if (lhs && TREE_CODE (lhs) == SSA_NAME)
+		    {
+		      tree var = create_tmp_var (TREE_TYPE (lhs), NULL);
+		      tree def = get_or_create_ssa_default_def (cfun, var);
+		      gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
+		      update_call_from_tree (gsi, def);
+		    }
+		  else
+		    gsi_replace (gsi, new_stmt, true);
 		  return true;
 		}
+
+	      gimple_call_set_fndecl (stmt, fndecl);
+	      changed = true;
 	    }
 	}
     }
--- gcc/testsuite/g++.dg/opt/pr59622-2.C.jj	2014-01-08 16:42:49.588747876 +0100
+++ gcc/testsuite/g++.dg/opt/pr59622-2.C	2014-01-08 16:42:49.588747876 +0100
@@ -0,0 +1,21 @@
+// PR tree-optimization/59622
+// { dg-do compile }
+// { dg-options "-O2" }
+
+namespace
+{
+  struct A
+  {
+    A () {}
+    virtual A *bar (int) = 0;
+    A *baz (int x) { return bar (x); }
+  };
+}
+
+A *a;
+
+void
+foo ()
+{
+  a->baz (0);
+}
--- gcc/testsuite/g++.dg/opt/pr59622-3.C.jj	2014-01-08 17:00:20.944359961 +0100
+++ gcc/testsuite/g++.dg/opt/pr59622-3.C	2014-01-08 17:00:44.558244745 +0100
@@ -0,0 +1,21 @@
+// PR tree-optimization/59622
+// { dg-do compile }
+// { dg-options "-O2" }
+
+struct C { int a; int b; };
+
+namespace
+{
+  struct A
+  {
+    virtual C foo ();
+    C bar () { return foo (); }
+  };
+}
+
+C
+baz ()
+{
+  A a;
+  return a.bar ();
+}
--- gcc/testsuite/g++.dg/opt/pr59622-4.C.jj	2014-01-08 17:00:54.332188462 +0100
+++ gcc/testsuite/g++.dg/opt/pr59622-4.C	2014-01-08 17:01:41.113947431 +0100
@@ -0,0 +1,23 @@
+// PR tree-optimization/59622
+// { dg-do compile }
+// { dg-options "-O2" }
+
+struct C { int a; int b; };
+
+namespace
+{
+  struct A
+  {
+    A () {}
+    virtual C bar (int) = 0;
+    C baz (int x) { return bar (x); }
+  };
+}
+
+A *a;
+
+C
+foo ()
+{
+  return a->baz (0);
+}


	Jakub



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