re PR c/56566 (bogus "is narrower than values of its type" warning)

	PR c/56566
	* tree.c (tree_int_cst_min_precision): For integer_zerop (value)
	return 1 even for !unsignedp.

	* c-c++-common/pr56566.c: New test.

From-SVN: r196767

1 files changed, 5 insertions, 7 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index 98ad5d8..31f8037 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -6648,8 +6648,6 @@ tree_int_cst_sgn (const_tree t)
 unsigned int
 tree_int_cst_min_precision (tree value, bool unsignedp)
 {
-  int log;
-
   /* If the value is negative, compute its negative minus 1.  The latter
      adjustment is because the absolute value of the largest negative value
      is one larger than the largest positive value.  This is equivalent to
@@ -6659,14 +6657,14 @@ tree_int_cst_min_precision (tree value, bool unsignedp)
     value = fold_build1 (BIT_NOT_EXPR, TREE_TYPE (value), value);
 
   /* Return the number of bits needed, taking into account the fact
-     that we need one more bit for a signed than unsigned type.  */
+     that we need one more bit for a signed than unsigned type.
+     If value is 0 or -1, the minimum precision is 1 no matter
+     whether unsignedp is true or false.  */
 
   if (integer_zerop (value))
-    log = 0;
+    return 1;
   else
-    log = tree_floor_log2 (value);
-
-  return log + 1 + !unsignedp;
+    return tree_floor_log2 (value) + 1 + !unsignedp;
 }
 
 /* Compare two constructor-element-type constants.  Return 1 if the lists