[backport gcc-4.8/trunk r185586 <mikpe@it.uu.se>]

gcc/

2012-04-19   Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c/52283/37985
	* stmt.c (warn_if_unused_value): Skip NOP_EXPR.
	* convert.c (convert_to_integer): Don't set TREE_NO_WARNING.

gcc/testsuite/

2012-04-19  Christian Bruel  <christian.bruel@st.com>

	* gcc.dg/pr52283.c: New test.

2012-04-19   Manuel López-Ibáñez  <manu@gcc.gnu.org>

	* gcc.dg/pr37985.c: New test.

--- gcc-4.7.2/gcc/convert.c.~1~	2012-04-27 12:51:58.000000000 +0200
+++ gcc-4.7.2/gcc/convert.c	2012-12-09 18:40:38.000000000 +0100
@@ -583,7 +583,6 @@ convert_to_integer (tree type, tree expr
       else if (outprec >= inprec)
 	{
 	  enum tree_code code;
-	  tree tem;
 
 	  /* If the precision of the EXPR's type is K bits and the
 	     destination mode has more bits, and the sign is changing,
@@ -601,13 +600,7 @@ convert_to_integer (tree type, tree expr
 	  else
 	    code = NOP_EXPR;
 
-	  tem = fold_unary (code, type, expr);
-	  if (tem)
-	    return tem;
-
-	  tem = build1 (code, type, expr);
-	  TREE_NO_WARNING (tem) = 1;
-	  return tem;
+	  return fold_build1 (code, type, expr);
 	}
 
       /* If TYPE is an enumeral type or a type with a precision less
--- gcc-4.7.2/gcc/stmt.c.~1~	2012-01-05 21:18:15.000000000 +0100
+++ gcc-4.7.2/gcc/stmt.c	2012-12-09 18:43:50.000000000 +0100
@@ -1515,6 +1515,7 @@ warn_if_unused_value (const_tree exp, lo
 
     case SAVE_EXPR:
     case NON_LVALUE_EXPR:
+    case NOP_EXPR:
       exp = TREE_OPERAND (exp, 0);
       goto restart;
 
--- gcc-4.7.2/gcc/testsuite/gcc.dg/pr37985.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.7.2/gcc/testsuite/gcc.dg/pr37985.c	2012-12-09 18:40:38.000000000 +0100
@@ -0,0 +1,8 @@
+/* PR c37985 */
+/* { dg-do compile } */
+/* { dg-options " -Wall -Wextra " } */
+unsigned char foo(unsigned char a)
+{
+  a >> 2; /* { dg-warning "no effect" } */
+  return a;
+}
--- gcc-4.7.2/gcc/testsuite/gcc.dg/pr52283.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.7.2/gcc/testsuite/gcc.dg/pr52283.c	2012-12-09 18:40:38.000000000 +0100
@@ -0,0 +1,16 @@
+/* Test for case labels not integer constant expressions but folding
+   to integer constants (used in Linux kernel).  */
+/* { dg-do compile } */
+
+extern unsigned int u;
+
+void
+b (int c)
+{
+  switch (c)
+    {
+    case (int) (2  | ((4 < 8) ? 8 : u)):
+      ;
+    }
+}
+