Re: gcc const int expressions and negative constants

[Geoff Keating <geoffk at cygnus dot com>]

> Date: Fri, 18 Aug 2000 00:00:19 +0100
> From: Neil Booth <NeilB@earthling.net>

> (insn 21 20 22 (set (reg:CC 17 flags)
>         (compare:CC (reg/v:QI 42)
>             (const_int 255 [0xff]))) -1 (nil)
>     (nil))
> 
> That should read (const_int -1 [0xffffffff]) ?

Yes.  

> If that's true, I was in quite the wrong place in combine.c.  I'll
> have a look at the RTL generation.  I think there's at least 3 bugs in
> GNATs that have the same root cause as this one.

Probably.

It may be a known problem with trunc_int_for_mode.  See
<http://gcc.gnu.org/ml/gcc-patches/2000-08/msg00360.html> and
follow-ups and the original message.

-- 
- Geoffrey Keating <geoffk@cygnus.com>