On Tue, Apr 29, 2025 at 12:56 PM Hongtao Liu <crazy...@gmail.com> wrote:
>
> On Sun, Apr 27, 2025 at 10:58 AM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > When passing 0xff as an unsigned char function argument with the C frontend
> > promotion, expand_normal used to get
> >
> > <integer_cst 0x7fffe6aa23a8 type <integer_type 0x7fffe98225e8 int> constant 
> > 255>
> >
> > and returned the rtx value using the sign-extended representation:
> >
> > (const_int 255 [0xff])
> >
> > But after
> >
> > commit a670ebde3995481225ec62b29686ec07a21e5c10
> > Author: H.J. Lu <hjl.to...@gmail.com>
> > Date:   Thu Nov 21 07:54:35 2024 +0800
> >
> >     Drop targetm.promote_prototypes from C, C++ and Ada frontends
> >
> > expand_normal now gets
> >
> > <integer_cst 0x7fffe9824018 type <integer_type 0x7fffe9822348 unsigned char 
> > > co
> > nstant 255>
> >
> > and returns
> >
> >      (const_int -1 [0xffffffffffffffff])
> It sounds like a general issue which should be fixed in expand_normal
> instead of fixing it in the backend?

It is related to trunc_int_for_mode.  I think this is a backend issue.

> >
> > which doesn't work with the predicates nor the instruction templates which
> > expect the unsigned expanded value.  Extract the unsigned char and short
> > integer constants to return
> >
> > (const_int 255 [0xff])
> >
> > so that the expanded value is always unsigned, without the C frontend
> > promotion.
> >
> > PR target/117547
> > * config/i386/i386-expand.cc (ix86_expand_unsigned_small_int_cst_argumen
> > t):
> > New function.
> > (ix86_expand_args_builtin): Call
> > ix86_expand_unsigned_small_int_cst_argument to expand the argument
> > before calling fixup_modeless_constant.
> > (ix86_expand_round_builtin): Likewise.
> > (ix86_expand_special_args_builtin): Likewise.
> > (ix86_expand_builtin): Likewise.
> >
> > --
> > H.J.
>
>
>
> --
> BR,
> Hongtao



-- 
H.J.

Reply via email to