Fix PR37418

[Richard Guenther]

This fixes PR37418, the fix was discussed at length about a month ago,
I just picked up the testcases from Josephs patch and used my tweak
to the type system.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2008-10-16  Richard Guenther  <rguenther@suse.de>

	PR middle-end/37418
	* tree-ssa.c (useless_type_conversion_p_1): Do not treat
	volatile qualified functions or methods as relevant.

testsuite:
2008-10-16  Joseph Myers  <joseph@codesourcery.com>

	PR middle-end/37418
	* gcc.c-torture/compile/pr37418-1.c,
	gcc.c-torture/compile/pr37418-2.c,
	gcc.c-torture/compile/pr37418-3.c,
	gcc.c-torture/compile/pr37418-4.c: New tests.

Index: gcc/testsuite/gcc.c-torture/compile/pr37418-1.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/pr37418-1.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/pr37418-1.c	(revision 0)
@@ -0,0 +1,6 @@
+typedef void ft(int);
+void f(int args)__attribute__((noreturn));
+void f2(ft *p __attribute__((noreturn)))
+{
+  p = f;
+}
Index: gcc/testsuite/gcc.c-torture/compile/pr37418-2.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/pr37418-2.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/pr37418-2.c	(revision 0)
@@ -0,0 +1,6 @@
+typedef void ft(int);
+volatile ft f;
+void f2(ft *p __attribute__((noreturn)))
+{
+  p = f;
+}
Index: gcc/testsuite/gcc.c-torture/compile/pr37418-3.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/pr37418-3.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/pr37418-3.c	(revision 0)
@@ -0,0 +1,6 @@
+typedef void ft(int);
+void f(int args)__attribute__((const));
+void f2(ft *p __attribute__((const)))
+{
+  p = f;
+}
Index: gcc/testsuite/gcc.c-torture/compile/pr37418-4.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/pr37418-4.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/pr37418-4.c	(revision 0)
@@ -0,0 +1,6 @@
+typedef void ft(int);
+const ft f;
+void f2(ft *p __attribute__((const)))
+{
+  p = f;
+}

Index: gcc/tree-ssa.c
===================================================================
*** gcc/tree-ssa.c	(revision 141150)
--- gcc/tree-ssa.c	(working copy)
*************** useless_type_conversion_p_1 (tree outer_
*** 1125,1133 ****
      {
        /* Don't lose casts between pointers to volatile and non-volatile
  	 qualified types.  Doing so would result in changing the semantics
! 	 of later accesses.  */
!       if ((TYPE_VOLATILE (TREE_TYPE (outer_type))
! 	   != TYPE_VOLATILE (TREE_TYPE (inner_type)))
  	  && TYPE_VOLATILE (TREE_TYPE (outer_type)))
  	return false;
  
--- 1125,1138 ----
      {
        /* Don't lose casts between pointers to volatile and non-volatile
  	 qualified types.  Doing so would result in changing the semantics
! 	 of later accesses.  For function types the volatile qualifier
! 	 is used to indicate noreturn functions.  */
!       if (TREE_CODE (TREE_TYPE (outer_type)) != FUNCTION_TYPE
! 	  && TREE_CODE (TREE_TYPE (outer_type)) != METHOD_TYPE
! 	  && TREE_CODE (TREE_TYPE (inner_type)) != FUNCTION_TYPE
! 	  && TREE_CODE (TREE_TYPE (inner_type)) != METHOD_TYPE
! 	  && (TYPE_VOLATILE (TREE_TYPE (outer_type))
! 	      != TYPE_VOLATILE (TREE_TYPE (inner_type)))
  	  && TYPE_VOLATILE (TREE_TYPE (outer_type)))
  	return false;