More NON_LVALUE_EXPR and NOP stripping cleanup

["Joseph S. Myers" <joseph at codesourcery dot com>]

This patch does further cleanup preliminary to removing the C front
end's dependence on NON_LVALUE_EXPR.

Stripping NON_LVALUE_EXPR is removed from
handle_vector_size_attribute; it can't occur for integer constants
there and the comment suggesting it might was nonsense (and there is
already a testcase with an expression like that in the comment in a
vector_size attribute).  Several places which manually stripped
NON_LVALUE_EXPR and sometimes other nops are changed to use
STRIP_TYPE_NOPS.  Inaccurate comments about enumerators with value 0
as null pointer constants are removed; such enumerators are null
pointer constants and are correctly handled as such.

Bootstrapped with no regressions on x86_64-unknown-linux-gnu.  Applied
to mainline.

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
    jsm@polyomino.org.uk (personal mail)
    joseph@codesourcery.com (CodeSourcery mail)
    jsm28@gcc.gnu.org (Bugzilla assignments and CCs)

2005-03-20  Joseph S. Myers  <joseph@codesourcery.com>

	* c-common.c (check_case_value): Adjust comment about stripping
	NOPs.
	(handle_vector_size_attribute): Don't strip NON_LVALUE_EXPR.
	* c-typeck.c (default_conversion, convert_arguments,
	build_modify_expr, convert_for_assignment, store_init_value,
	digest_init): Use STRIP_TYPE_NOPS instead of stripping nops
	manually.  Remove inaccurate comments.

diff -rupN GCC.orig/gcc/c-common.c GCC/gcc/c-common.c
--- GCC.orig/gcc/c-common.c	2005-03-20 15:21:09.000000000 +0000
+++ GCC/gcc/c-common.c	2005-03-20 20:51:44.000000000 +0000
@@ -1411,7 +1411,8 @@ check_case_value (tree value)
   if (value == NULL_TREE)
     return value;
 
-  /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
+  /* ??? Can we ever get nops here for a valid case value?  We
+     shouldn't for C.  */
   STRIP_TYPE_NOPS (value);
   /* In C++, the following is allowed:
 
@@ -4934,11 +4935,7 @@ handle_vector_size_attribute (tree *node
 
   *no_add_attrs = true;
 
-  /* Stripping NON_LVALUE_EXPR allows declarations such as
-     typedef short v4si __attribute__((vector_size (4 * sizeof(short)))).  */
   size = TREE_VALUE (args);
-  if (TREE_CODE (size) == NON_LVALUE_EXPR)
-    size = TREE_OPERAND (size, 0);
 
   if (!host_integerp (size, 1))
     {
diff -rupN GCC.orig/gcc/c-typeck.c GCC/gcc/c-typeck.c
--- GCC.orig/gcc/c-typeck.c	2005-03-20 15:21:10.000000000 +0000
+++ GCC/gcc/c-typeck.c	2005-03-20 21:05:53.000000000 +0000
@@ -1378,16 +1378,9 @@ default_conversion (tree exp)
       type = TREE_TYPE (exp);
     }
 
-  /* Strip NON_LVALUE_EXPRs and no-op conversions, since we aren't using as
-     an lvalue.
-
-     Do not use STRIP_NOPS here!  It will remove conversions from pointer
-     to integer and cause infinite recursion.  */
+  /* Strip no-op conversions.  */
   orig_exp = exp;
-  while (TREE_CODE (exp) == NON_LVALUE_EXPR
-	 || (TREE_CODE (exp) == NOP_EXPR
-	     && TREE_TYPE (TREE_OPERAND (exp, 0)) == TREE_TYPE (exp)))
-    exp = TREE_OPERAND (exp, 0);
+  STRIP_TYPE_NOPS (exp);
 
   if (TREE_NO_WARNING (orig_exp))
     TREE_NO_WARNING (exp) = 1;
@@ -2133,11 +2126,7 @@ convert_arguments (tree typelist, tree v
 	  argnum -= 2;
 	}
 
-      /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
-      /* Do not use STRIP_NOPS here!  We do not want an enumerator with value 0
-	 to convert automatically to a pointer.  */
-      if (TREE_CODE (val) == NON_LVALUE_EXPR)
-	val = TREE_OPERAND (val, 0);
+      STRIP_TYPE_NOPS (val);
 
       val = default_function_array_conversion (val);
 
@@ -3349,11 +3338,7 @@ build_modify_expr (tree lhs, enum tree_c
   if (TREE_CODE (lhs) == ERROR_MARK || TREE_CODE (rhs) == ERROR_MARK)
     return error_mark_node;
 
-  /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
-  /* Do not use STRIP_NOPS here.  We do not want an enumerator
-     whose value is 0 to count as a null pointer constant.  */
-  if (TREE_CODE (rhs) == NON_LVALUE_EXPR)
-    rhs = TREE_OPERAND (rhs, 0);
+  STRIP_TYPE_NOPS (rhs);
 
   newrhs = rhs;
 
@@ -3487,11 +3472,7 @@ convert_for_assignment (tree type, tree 
       }						\
   } while (0)
 
-  /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
-  /* Do not use STRIP_NOPS here.  We do not want an enumerator
-     whose value is 0 to count as a null pointer constant.  */
-  if (TREE_CODE (rhs) == NON_LVALUE_EXPR)
-    rhs = TREE_OPERAND (rhs, 0);
+  STRIP_TYPE_NOPS (rhs);
 
   if (TREE_CODE (TREE_TYPE (rhs)) == ARRAY_TYPE
       || TREE_CODE (TREE_TYPE (rhs)) == FUNCTION_TYPE)
@@ -3933,8 +3914,7 @@ store_init_value (tree decl, tree init)
     {
       tree inside_init = init;
 
-      if (TREE_CODE (init) == NON_LVALUE_EXPR)
-	inside_init = TREE_OPERAND (init, 0);
+      STRIP_TYPE_NOPS (inside_init);
       inside_init = fold (inside_init);
 
       if (TREE_CODE (inside_init) == COMPOUND_LITERAL_EXPR)
@@ -4154,11 +4134,7 @@ digest_init (tree type, tree init, bool 
       || TREE_TYPE (init) == error_mark_node)
     return error_mark_node;
 
-  /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
-  /* Do not use STRIP_NOPS here.  We do not want an enumerator
-     whose value is 0 to count as a null pointer constant.  */
-  if (TREE_CODE (init) == NON_LVALUE_EXPR)
-    inside_init = TREE_OPERAND (init, 0);
+  STRIP_TYPE_NOPS (inside_init);
 
   inside_init = fold (inside_init);