On Fri, Jul 18, 2025, at 9:45 AM, Hans-Peter Nilsson wrote: > From: Hans-Peter Nilsson <h...@bitrange.com> > > This has an effect only for MMIX and BPF. All other targets are > either 32-bits-or-less BITS_PER_WORD (and will now get 64 just > by a more obvious expression), or they don't use the default > MAX_FIXED_MODE_SIZE. > > I can't build a complete toolchain for BPF (fails building > libgcc, PR121149), but from what I can see with that build, > having MAX_FIXED_MODE_SIZE 64 is unintended: TImode isn't > disabled for BPF. So, I'm not offering a patch to keep > MAX_FIXED_MODE_SIZE 64 for BPF; with this patch, it moves to 2 * > BITS_PER_WORD == 128 as all other 64-bitters. > > (BTW, disabling TImode and building an unmodified libgcc for a > target with MIN_UNITS_PER_WORD > 4 is not currently possible.) > > Tested cris-elf (using the "new" default) and MMIX (fixing > gcc.dg/pr105094.c and incidentally PR 120935, where there's a > more proper patch proposed) and native x86_64 (though it doesn't > use the default at all). > > Ok for master? > > -- >8 -- > The old GET_MODE_SIZE (DImode) (i.e. 64) made sense before > 64-bitters. Now the default is just a trap: when using the > default 64, things like TImode (128 bits) still mostly works, > but general corner cases related to computing large-size objects > numbers, like (1 << 64)/8 break, as exposed by > gcc.dg/pr105094.c. > > So, keep the floor at 64 for 32-bitters and smaller targets, but > for larger targets, make it 2 * BITS_PER_WORD. Also, express it > more directly with focus on BITS_PER_WORD, not the size of a mode. > > * defaults.h (MAX_FIXED_MODE_SIZE): Default to 2 * BITS_PER_WORD > for larger-than-32-bitters.
I think you need to update the description of MAX_FIXED_MODE_SIZE in gcc/doc/tm.texi.in with the new default. pietro > --- > gcc/defaults.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/gcc/defaults.h b/gcc/defaults.h > index 16f6dc24e3b8..f807ef667e6d 100644 > --- a/gcc/defaults.h > +++ b/gcc/defaults.h > @@ -1158,7 +1158,7 @@ see the files COPYING3 and COPYING.RUNTIME > respectively. If not, see > #endif > > #ifndef MAX_FIXED_MODE_SIZE > -#define MAX_FIXED_MODE_SIZE GET_MODE_BITSIZE (DImode) > +#define MAX_FIXED_MODE_SIZE MAX (BITS_PER_WORD * 2, 64) > #endif > > /* Nonzero if structures and unions should be returned in memory. > -- > 2.39.2
