PR middle-end/58564

	* fold-const.c (fold_ternary_loc): For A < 0 : <sign bit of A> : 0
	optimization, punt if sign_bit_p looked through any zero extension.

	* gcc.c-torture/execute/pr58564.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@203042 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 17 insertions, 2 deletions

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 72a43e04a44..f68fd8b15d5 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -14196,14 +14196,29 @@ fold_ternary_loc (location_t loc, enum tree_code code, tree type,
 	  && integer_zerop (op2)
 	  && (tem = sign_bit_p (TREE_OPERAND (arg0, 0), arg1)))
 	{
+	  /* sign_bit_p looks through both zero and sign extensions,
+	     but for this optimization only sign extensions are
+	     usable.  */
+	  tree tem2 = TREE_OPERAND (arg0, 0);
+	  while (tem != tem2)
+	    {
+	      if (TREE_CODE (tem2) != NOP_EXPR
+		  || TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (tem2, 0))))
+		{
+		  tem = NULL_TREE;
+		  break;
+		}
+	      tem2 = TREE_OPERAND (tem2, 0);
+	    }
 	  /* sign_bit_p only checks ARG1 bits within A's precision.
 	     If <sign bit of A> has wider type than A, bits outside
 	     of A's precision in <sign bit of A> need to be checked.
 	     If they are all 0, this optimization needs to be done
 	     in unsigned A's type, if they are all 1 in signed A's type,
 	     otherwise this can't be done.  */
-	  if (TYPE_PRECISION (TREE_TYPE (tem))
-	      < TYPE_PRECISION (TREE_TYPE (arg1))
+	  if (tem
+	      && TYPE_PRECISION (TREE_TYPE (tem))
+		 < TYPE_PRECISION (TREE_TYPE (arg1))
 	      && TYPE_PRECISION (TREE_TYPE (tem))
 		 < TYPE_PRECISION (type))
 	    {