On Mon, Jan 31, 2022 at 7:01 PM Richard Sandiford via Gcc-patches <
gcc-patches@gcc.gnu.org> wrote:
> Sorry for the slow response, was out last week.
>
> Christophe Lyon via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> > diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
> > index feeee16d320..5f559f8fd93 100644
> > --- a/gcc/emit-rtl.c
> > +++ b/gcc/emit-rtl.c
> > @@ -6239,9 +6239,14 @@ init_emit_once (void)
> >
> > /* For BImode, 1 and -1 are unsigned and signed interpretations
> > of the same value. */
> > - const_tiny_rtx[0][(int) BImode] = const0_rtx;
> > - const_tiny_rtx[1][(int) BImode] = const_true_rtx;
> > - const_tiny_rtx[3][(int) BImode] = const_true_rtx;
> > + for (mode = MIN_MODE_BOOL;
> > + mode <= MAX_MODE_BOOL;
> > + mode = (machine_mode)((int)(mode) + 1))
> > + {
> > + const_tiny_rtx[0][(int) mode] = const0_rtx;
> > + const_tiny_rtx[1][(int) mode] = const_true_rtx;
> > + const_tiny_rtx[3][(int) mode] = const_true_rtx;
> > + }
> >
> > for (mode = MIN_MODE_PARTIAL_INT;
> > mode <= MAX_MODE_PARTIAL_INT;
>
> Does this do the right thing for:
>
> gen_int_mode (-1, B2Imode)
>
> (which is used e.g. in native_decode_vector_rtx)? It looks like it
> would give 0b01 rather than 0b11.
>
> Maybe for non-BImode we should use const1_rtx and constm1_rtx, like with
> MODE_INT.
>
debug_rtx ( gen_int_mode (-1, B2Imode) says:
(const_int -1 [0xffffffffffffffff])
so that looks right?
> > @@ -1298,9 +1315,21 @@ enum machine_mode\n{");
> > /* Don't use BImode for MIN_MODE_INT, since otherwise the middle
> > end will try to use it for bitfields in structures and the
> > like, which we do not want. Only the target md file should
> > - generate BImode widgets. */
> > - if (first && first->precision == 1 && c == MODE_INT)
> > - first = first->next;
> > + generate BImode widgets. Since some targets such as ARM/MVE
> > + define boolean modes with multiple bits, handle those too. */
> > + if (first && first->boolean)
> > + {
> > + struct mode_data *last_bool = first;
> > + printf (" MIN_MODE_BOOL = E_%smode,\n", first->name);
> > +
> > + while (first && first->boolean)
> > + {
> > + last_bool = first;
> > + first = first->next;
> > + }
> > +
> > + printf (" MAX_MODE_BOOL = E_%smode,\n\n", last_bool->name);
> > + }
> >
> > if (first && last)
> > printf (" MIN_%s = E_%smode,\n MAX_%s = E_%smode,\n\n",
>
> For the record: this means that MIN_MODE_BOOL and MAX_MODE_BOOL are
> in principle only conditionally available, whereas:
>
> /* For BImode, 1 and -1 are unsigned and signed interpretations
> of the same value. */
> - const_tiny_rtx[0][(int) BImode] = const0_rtx;
> - const_tiny_rtx[1][(int) BImode] = const_true_rtx;
> - const_tiny_rtx[3][(int) BImode] = const_true_rtx;
> + for (mode = MIN_MODE_BOOL;
> + mode <= MAX_MODE_BOOL;
> + mode = (machine_mode)((int)(mode) + 1))
> + {
> + const_tiny_rtx[0][(int) mode] = const0_rtx;
> + const_tiny_rtx[1][(int) mode] = const_true_rtx;
> + const_tiny_rtx[3][(int) mode] = const_true_rtx;
> + }
>
> assumes that they are unconditionally available. In some ways it
> might be clearer if we assert that first->boolean is true and
> emit the MIN/MAX stuff unconditionally.
>
> However, that would make the generator less robust against malformed
> input, and it would probably be inconsistent with the current generator
> code, so I agree that the patch's version is better on balance.
>
ack
>
> > @@ -1679,15 +1708,25 @@ emit_class_narrowest_mode (void)
> > print_decl ("unsigned char", "class_narrowest_mode",
> "MAX_MODE_CLASS");
> >
> > for (c = 0; c < MAX_MODE_CLASS; c++)
> > - /* Bleah, all this to get the comment right for MIN_MODE_INT. */
> > - tagged_printf ("MIN_%s", mode_class_names[c],
> > - modes[c]
> > - ? ((c != MODE_INT || modes[c]->precision != 1)
> > - ? modes[c]->name
> > - : (modes[c]->next
> > - ? modes[c]->next->name
> > - : void_mode->name))
> > - : void_mode->name);
> > + {
> > + /* Bleah, all this to get the comment right for MIN_MODE_INT. */
> > + const char *comment_name = void_mode->name;
> > +
> > + if (modes[c])
> > + if (c != MODE_INT || !modes[c]->boolean)
> > + comment_name = modes[c]->name;
> > + else
> > + {
> > + struct mode_data *m = modes[c];
> > + while (m->boolean)
> > + m = m->next;
> > + if (m)
> > + comment_name = m->name;
> > + else
> > + comment_name = void_mode->name;
> > + }
>
> Have you tried bootstrapping the patch on a host of your choice?
> I would expect a warning/Werror about an ambiguous else here.
>
No I hadn't and indeed the build fails
>
> I guess this reduces to:
>
> struct mode_data *m = modes[c];
> while (m && m->boolean)
> m = m->next;
> const char *comment_name = (m ? m : void_mode)->name;
>
> but I don't know if that's more readable.
>
but to my understanding the problem is that the ambiguous else
is the first one, and the code should read:
if (modes[c])
+ {
if (c != MODE_INT || !modes[c]->boolean)
comment_name = modes[c]->name;
else
{
struct mode_data *m = modes[c];
while (m->boolean)
m = m->next;
if (m)
comment_name = m->name;
else
comment_name = void_mode->name;
}
+ }
LGTM otherwise.
>
Thanks.
Andre, what about you? Did you try my suggestion to use
ENTRY (Pred1x16_t, V16BI, predicate, 16, pred1, 21)
ENTRY (Pred2x8_t, V8BI, predicate, 8, pred1, 21)
ENTRY (Pred4x4_t, V4BI, predicate, 4, pred1, 21)
Does that work for you?
Christophe
> Thanks,
> Richard
>
