re PR tree-optimization/46076 (constant propagation and compile-time math no…

re PR tree-optimization/46076 (constant propagation and compile-time math no longer happening versus 4.4 and 4.5)

2011-01-11  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/46076
	* tree-ssa.c (useless_type_conversion_p): Conversions from
	unprototyped to empty argument list function types are useless.

	* gcc.dg/tree-ssa/pr46076.c: New testcase.

From-SVN: r168665

gcc/ChangeLog

 2011-01-11  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/46076
+	* tree-ssa.c (useless_type_conversion_p): Conversions from
+	unprototyped to empty argument list function types are useless.
+
+2011-01-11  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/45235
 	* emit-rtl.c (set_mem_attributes_minus_bitpos): Do not mark
 	volatile MEMs as MEM_READONLY_P.

gcc/testsuite/ChangeLog

+2011-01-11  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/46076
+	* gcc.dg/tree-ssa/pr46076.c: New testcase.
+
 2011-01-11  Jeff Law <law@redhat.com>
 
 	* PR tree-optimization/47086

gcc/testsuite/gcc.dg/tree-ssa/pr46076.c

+/* { dg-do link } */
+/* { dg-options "-O2" } */
+
+extern void link_error (void);
+
+typedef unsigned char(*Calculable)(void);
+
+static unsigned char one() { return 1; }
+static unsigned char two() { return 2; }
+
+static int
+print(Calculable calculate)
+{
+  return calculate() + calculate() + 1;
+}
+
+int
+main()
+{
+  /* Make sure we perform indirect inlining of one and two and optimize
+     the result to a constant.  */
+  if (print(one) != 3)
+    link_error ();
+  if (print(two) != 5)
+    link_error ();
+  return 0;
+}

gcc/tree-ssa.c

@@ -1410,6 +1410,11 @@ useless_type_conversion_p (tree outer_type, tree inner_type)
       if (!prototype_p (outer_type))
 	return true;
 
+      /* A conversion between unprototyped and empty argument list is ok.  */
+      if (TYPE_ARG_TYPES (outer_type) == void_list_node
+	  && !prototype_p (inner_type))
+	return true;
+
       /* If the unqualified argument types are compatible the conversion
 	 is useless.  */
       if (TYPE_ARG_TYPES (outer_type) == TYPE_ARG_TYPES (inner_type))