[trunk][patch] fix a bug in fold_call_expr and one in record_temporary_equivalences_from_stmts_at_dest

["Rafael Espindola" <espindola at google dot com>]

There is a missing return in fold_call_expr. This bug disables some
uses of jump threading. In particular, it disables jump threading
based on values returned by __builtin_object_size. This hides another
bug: One cannot use __builtin_object_size in jump threading. The
definition of __builtin_object_size makes its return value depend on
the existence of arguments to a phi node.

The patch fixes both bugs.

OK with a bootstrap and regression tests?

 * builtins.c (fold_call_expr): Return realret.
 * tree-ssa-threadedge.c
(record_temporary_equivalences_from_stmts_at_dest): Ignore calls to
__builtin_object_size.

Cheers,
-- 
Rafael Avila de Espindola

Google Ireland Ltd.
Gordon House
Barrow Street
Dublin 4
Ireland

Registered in Dublin, Ireland
Registration Number: 368047

diff --git a/gcc/builtins.c b/gcc/builtins.c
index 321032d..2cb8fa0 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -10553,6 +10553,7 @@ fold_call_expr (tree exp, bool ignore)
 		  if (CAN_HAVE_LOCATION_P (realret)
 		      && !EXPR_HAS_LOCATION (realret))
 		    SET_EXPR_LOCATION (realret, EXPR_LOCATION (exp));
+		  return realret;
 		}
 	      return ret;
 	    }
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index d0d8fb2..71aa91b 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -226,6 +226,7 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
   for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
     {
       tree cached_lhs = NULL;
+      tree rhs;
 
       stmt = bsi_stmt (bsi);
 
@@ -252,6 +253,18 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
 	  || TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 0)) != SSA_NAME)
 	continue;
 
+      rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+
+      /* The result of __builtin_object_size depends on all the arguments
+	 of a phi node. Temporally using only one edge produces invalid
+	 results. */
+      if (TREE_CODE (rhs) == CALL_EXPR)
+	{
+	  tree fndecl = get_callee_fndecl (rhs);
+	  if (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE)
+	    continue;
+	}
+
       /* At this point we have a statement which assigns an RHS to an
 	 SSA_VAR on the LHS.  We want to try and simplify this statement
 	 to expose more context sensitive equivalences which in turn may
@@ -259,10 +272,10 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
 
 	 Handle simple copy operations as well as implied copies from
 	 ASSERT_EXPRs.  */
-      if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == SSA_NAME)
-	cached_lhs = GIMPLE_STMT_OPERAND (stmt, 1);
-      else if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ASSERT_EXPR)
-	cached_lhs = TREE_OPERAND (GIMPLE_STMT_OPERAND (stmt, 1), 0);
+      if (TREE_CODE (rhs) == SSA_NAME)
+	cached_lhs = rhs;
+      else if (TREE_CODE (rhs) == ASSERT_EXPR)
+	cached_lhs = TREE_OPERAND (rhs, 0);
       else
 	{
 	  /* A statement that is not a trivial copy or ASSERT_EXPR.