integer_onep vs. signed 1-bit bitfields

[Jakub Jelinek]

On Sat, Nov 02, 2013 at 05:38:53PM +0000, Richard Sandiford wrote:
> OK, thanks.  I should have realised this earlier, but we have:
> 
> /* Return 1 if EXPR is the integer constant one or the corresponding
>    complex constant.  */
> 
> int
> integer_onep (const_tree expr)
> ...
> /* Return 1 if EXPR is the integer constant minus one.  */
> 
> int
> integer_minus_onep (const_tree expr)
> 
> which makes them sound like a pair.  But integer_minus_onep returns
> true for any all-ones INTEGER_CST (regardless of sign):
> 
>   if (TREE_CODE (expr) == COMPLEX_CST)
>     return (integer_all_onesp (TREE_REALPART (expr))
> 	    && integer_zerop (TREE_IMAGPART (expr)));
>   else
>     return integer_all_onesp (expr);
> 
> So a nonzero 1-bit unsigned bitfield is both integer_onep and
> integer_minus_onep, but a 1-bit signed bitfield is only
> integer_minus_onep.  Should integer_minus_onep be changed so
> that it always returns false for unsigned types?

Yeah, I was wondering about that too.  I think integer_minus_onep
is a fairly new thing, I guess if you want to change it, somebody has to go
through all users and see what they want.
Returning false for unsigned types is natural thing to do though.

	Jakub