Hi Hans.
Thank you for the heads up. I think it is ok to use the new default in BPF. It is extremely unlikely it will ever impact existing current BPF programs, and when/if it comes to that, it will help to use the best default so we can at that point formalize the ABI. > From: Hans-Peter Nilsson <h...@bitrange.com> > > The change of default value for MAX_FIXED_MODE_SIZE was > approved contingent on not changing it for BPF, since it > could not be trivially ruled out to change the ABI for a > target. See thread at > "https://gcc.gnu.org/pipermail/gcc-patches/2025-July/690288.html";. > > Since this change to set it to the (current) default is > obvious, by default I'll commit it in about a week as such, > but giving target maintainers a chance to chime in now. > > To check, set it to 128 for BPF, which I believe will give a > better target experience. If you agree that'll be better > and you don't see any ABI effects, just tell, and I'll *not* > commit this patch. If post-commit, then revert it, though > preferably not using git revert but with an explanatory > comment. I deliberately chose not to add any comment next to > the define: if you prefer one, please tell what you want there. > > Tested together with the above quoted patch for bpf-unknown-none > and --enable-languages=c observing no change in libgcc code or > test-results (those I can get without a simulator). A separate > build without this patch shows the expected improvements in > test-results but still no change in libgcc code. > > There might be a delay if you have any questions. > -- >8 -- > When the default is changed, the BPF target would be > affected, so this is the "no functional change" safe change, > defining as exactly the current default. Naive observations > of compiled code in libgcc that uses int128 types shows that > the default may be a better choice. > > * config/bpf/bpf.h (MAX_FIXED_MODE_SIZE): Define. > --- > gcc/config/bpf/bpf.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h > index 8fb55b08f03f..babf99f94094 100644 > --- a/gcc/config/bpf/bpf.h > +++ b/gcc/config/bpf/bpf.h > @@ -83,6 +83,8 @@ > `allocate_stack' pattern. */ > #define STACK_SIZE_MODE Pmode > > +#define MAX_FIXED_MODE_SIZE GET_MODE_BITSIZE (DImode) > + > /**** Layout of Source Language Data Types. */ > > #define INT_TYPE_SIZE 32
