[wide-int] Make integer_onep return false for signed 1-bit bitfields

[Richard Sandiford]

As discussed on gcc@, integer_onep is supposed to return false for
a nonzero 1-bit value if the type is signed.

Tested on x86_64-linux-gnu and powerpc64-linux-gnu.  OK to install?

Thanks,
Richard


Index: gcc/tree.c
===================================================================
--- gcc/tree.c  2013-10-29 19:19:27.623468618 +0000
+++ gcc/tree.c  2013-11-02 17:25:06.499657501 +0000
@@ -2092,7 +2092,7 @@ integer_onep (const_tree expr)
   switch (TREE_CODE (expr))
     {
     case INTEGER_CST:
-      return wi::eq_p (expr, 1);
+      return wi::eq_p (wi::to_widest (expr), 1);
     case COMPLEX_CST:
       return (integer_onep (TREE_REALPART (expr))
              && integer_zerop (TREE_IMAGPART (expr)));