re PR c/48418 (Bit shift operator >>=)

	PR c/48418
	* c-common.c (c_fully_fold_internal): Warn for LSHIFT_EXPR and
	RSHIFT_EXPR, if orig_op1 isn't INTEGER_CST, op1 is INTEGER_CST
	and is either negative or bigger or equal to type precision
	of the first operand.

	* typeck.c (cp_build_binary_op): For LSHIFT_EXPR and RSHIFT_EXPR,
	call maybe_constant_value for the negative or too big shift
	count warnings.

	* c-c++-common/pr48418.c: New test.

From-SVN: r195051

gcc/c-family/ChangeLog

+2013-01-09  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/48418
+	* c-common.c (c_fully_fold_internal): Warn for LSHIFT_EXPR and
+	RSHIFT_EXPR, if orig_op1 isn't INTEGER_CST, op1 is INTEGER_CST
+	and is either negative or bigger or equal to type precision
+	of the first operand.
+
 2012-12-03  Marek Polacek  <polacek@redhat.com>
 
 	PR c/55570

gcc/c-family/c-common.c

 /* Subroutines shared by all languages that are variants of C.
    Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
-   Free Software Foundation, Inc.
+   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012,
+   2013 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -1269,6 +1269,25 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
 	  && !TREE_OVERFLOW_P (op0)
 	  && !TREE_OVERFLOW_P (op1))
 	overflow_warning (EXPR_LOCATION (expr), ret);
+      if ((code == LSHIFT_EXPR || code == RSHIFT_EXPR)
+	  && TREE_CODE (orig_op1) != INTEGER_CST
+	  && TREE_CODE (op1) == INTEGER_CST
+	  && (TREE_CODE (TREE_TYPE (orig_op0)) == INTEGER_TYPE
+	      || TREE_CODE (TREE_TYPE (orig_op0)) == FIXED_POINT_TYPE)
+	  && TREE_CODE (TREE_TYPE (orig_op1)) == INTEGER_TYPE
+	  && c_inhibit_evaluation_warnings == 0)
+	{
+	  if (tree_int_cst_sgn (op1) < 0)
+	    warning_at (loc, 0, (code == LSHIFT_EXPR
+				 ? G_("left shift count is negative")
+				 : G_("right shift count is negative")));
+	  else if (compare_tree_int (op1,
+				     TYPE_PRECISION (TREE_TYPE (orig_op0)))
+		   >= 0)
+	    warning_at (loc, 0, (code == LSHIFT_EXPR
+				 ? G_("left shift count >= width of type")
+				 : G_("right shift count >= width of type")));
+	}
       goto out;
 
     case INDIRECT_REF:

gcc/cp/ChangeLog

+2013-01-09  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/48418
+	* typeck.c (cp_build_binary_op): For LSHIFT_EXPR and RSHIFT_EXPR,
+	call maybe_constant_value for the negative or too big shift
+	count warnings.
+
 2013-01-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/55801

gcc/cp/typeck.c

 /* Build expressions with type checking for C++ compiler.
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
-   2011, 2012
+   2011, 2012, 2013
    Free Software Foundation, Inc.
    Hacked by Michael Tiemann (tiemann@cygnus.com)
 
@@ -4095,10 +4095,13 @@ cp_build_binary_op (location_t location,
 	}
       else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
 	{
+	  tree const_op1 = maybe_constant_value (op1);
+	  if (TREE_CODE (const_op1) != INTEGER_CST)
+	    const_op1 = op1;
 	  result_type = type0;
-	  if (TREE_CODE (op1) == INTEGER_CST)
+	  if (TREE_CODE (const_op1) == INTEGER_CST)
 	    {
-	      if (tree_int_cst_lt (op1, integer_zero_node))
+	      if (tree_int_cst_lt (const_op1, integer_zero_node))
 		{
 		  if ((complain & tf_warning)
 		      && c_inhibit_evaluation_warnings == 0)
@@ -4106,7 +4109,7 @@ cp_build_binary_op (location_t location,
 		}
 	      else
 		{
-		  if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0
+		  if (compare_tree_int (const_op1, TYPE_PRECISION (type0)) >= 0
 		      && (complain & tf_warning)
 		      && c_inhibit_evaluation_warnings == 0)
 		    warning (0, "right shift count >= width of type");
@@ -4138,16 +4141,20 @@ cp_build_binary_op (location_t location,
 	}
       else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
 	{
+	  tree const_op1 = maybe_constant_value (op1);
+	  if (TREE_CODE (const_op1) != INTEGER_CST)
+	    const_op1 = op1;
 	  result_type = type0;
-	  if (TREE_CODE (op1) == INTEGER_CST)
+	  if (TREE_CODE (const_op1) == INTEGER_CST)
 	    {
-	      if (tree_int_cst_lt (op1, integer_zero_node))
+	      if (tree_int_cst_lt (const_op1, integer_zero_node))
 		{
 		  if ((complain & tf_warning)
 		      && c_inhibit_evaluation_warnings == 0)
 		    warning (0, "left shift count is negative");
 		}
-	      else if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0)
+	      else if (compare_tree_int (const_op1,
+					 TYPE_PRECISION (type0)) >= 0)
 		{
 		  if ((complain & tf_warning)
 		      && c_inhibit_evaluation_warnings == 0)

gcc/testsuite/ChangeLog

+2013-01-09  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/48418
+	* c-c++-common/pr48418.c: New test.
+
 2013-01-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/55801

gcc/testsuite/c-c++-common/pr48418.c

+/* PR c/48418 */
+/* { dg-do compile } */
+/* { dg-options "-Wall -O2" } */
+
+int
+foo (int x)
+{
+  const int a = sizeof (int) * __CHAR_BIT__;
+  const int b = -7;
+  int c = 0;
+  c += x << a;				   /* { dg-warning "left shift count >= width of type" } */
+  c += x << b;				   /* { dg-warning "left shift count is negative" } */
+  c += x << (sizeof (int) * __CHAR_BIT__); /* { dg-warning "left shift count >= width of type" } */
+  c += x << -7;				   /* { dg-warning "left shift count is negative" } */
+  c += x >> a;				   /* { dg-warning "right shift count >= width of type" } */
+  c += x >> b;				   /* { dg-warning "right shift count is negative" } */
+  c += x >> (sizeof (int) * __CHAR_BIT__); /* { dg-warning "right shift count >= width of type" } */
+  c += x >> -7;				   /* { dg-warning "right shift count is negative" } */
+  return c;
+}