On Wed, Nov 19, 2014 at 10:38:57AM -0800, Mike Stump wrote:
> On Nov 19, 2014, at 4:24 AM, Richard Biener <[email protected]> wrote:
> > On Wed, 19 Nov 2014, Jakub Jelinek wrote:
> >> For TARGET_SUPPORTS_WIDE_INT == 0 should be hopefully ok. Not sure
> >> about TARGET_SUPPORTS_WIDE_INT != 0, can it express any generic_wide_int,
> >> or
> >> is it still bound to wide_int (i.e. MAX_BITSIZE_MODE_ANY_INT rounded up)
> >> precision? Mike?
> >
> > It can represent any - well, the RTX at least. Code then using
> > "simple" wide_int may wreck then though.
>
> So, my worry is this… once you start in on adding support here or there
> for int modes wider than the largest supported int mode, you create a
> never ending maintenance nightmare with complex rules that one will never
> be able to keep straight. There needs to be a single line or two, that
> explains the rules that we all agree to, then it will always be clear what
> the rule is. The largest supported int mode is: x, has a nice, simple,
> easy to explain aspect to it.
Well, at least for TARGET_SUPPORTS_WIDE_INT == 0 my patch would always
create CONST_INTs or CONST_DOUBLEs, which all fit into
MAX_BITSIZE_MODE_ANY_INT bits, CONST_INTs are modeless, so in what wider
mode you use them doesn't matter. For TARGET_SUPPORTS_WIDE_INT != 0
we could certainly cap it similarly, if wi::min_precision (r, SIGNED) >
MAX_BITSIZE_MODE_ANY_INT we could return NULL_RTX.
Though, following patch is just fine for me too, I don't think it will
make a significant difference:
--- gcc/simplify-rtx.c 2014-11-19 15:39:24.073113107 +0100
+++ gcc/simplify-rtx.c 2014-11-19 22:55:44.201464253 +0100
@@ -5504,6 +5504,8 @@ simplify_immed_subreg (machine_mode oute
HOST_WIDE_INT tmp[MAX_BITSIZE_MODE_ANY_INT /
HOST_BITS_PER_WIDE_INT];
wide_int r;
+ if (GET_MODE_PRECISION (outer_submode) > MAX_BITSIZE_MODE_ANY_INT)
+ return NULL_RTX;
for (u = 0; u < units; u++)
{
unsigned HOST_WIDE_INT buf = 0;
@@ -5515,10 +5517,13 @@ simplify_immed_subreg (machine_mode oute
tmp[u] = buf;
base += HOST_BITS_PER_WIDE_INT;
}
- gcc_assert (GET_MODE_PRECISION (outer_submode)
- <= MAX_BITSIZE_MODE_ANY_INT);
r = wide_int::from_array (tmp, units,
GET_MODE_PRECISION (outer_submode));
+#if TARGET_SUPPORTS_WIDE_INT == 0
+ /* Make sure r will fit into CONST_INT or CONST_DOUBLE. */
+ if (wi::min_precision (r, SIGNED) > HOST_BITS_PER_DOUBLE_INT)
+ return NULL_RTX;
+#endif
elems[elem] = immed_wide_int_const (r, outer_submode);
}
break;
Jakub
