Re: [PATCH] MIPS: use arch_32/64 instead of default_mips_arch

[YunQiang Su <syq@debian.org>]

Xi Ruoyao via Gcc-patches <gcc-patches@gcc.gnu.org> 于2023年2月3日周五 22:35写道：
>
> On Fri, 2023-02-03 at 14:08 +0000, Richard Sandiford via Gcc-patches
> wrote:
> > > Do you mean that the "wrong" format is quite interesting?
> > > Yes, While this format is never used at all.
> >
> > My point was that there is nothing wrong in principle with creating
> > an o32 executable that has a 64-bit rather than a 32-bit ISA (since
> > the
> > 64-bit ISAs are pure extensions of 32-bit ISAs).  Doing that is even
> > useful in some cases.  For example, MIPS4+O32 is a useful combination,
> > even though MIPS4 is a 64-bit ISA.  Same for Octeon3+O32, etc.
> >
> > So is the linker behaviour really correct?  Doesn't it mean that
> > Octeon3 O32 binaries are link-incompatible with MIPS32 o32 binaries?
>
> On gcc230:
>
> xry111@gcc230:~$ cat a.c
> int a() { return 42; }
> xry111@gcc230:~$ cat b.c
> extern int a(void);
> int main() { return a() ^ 42; }
> xry111@gcc230:~$ cc a.c -mabi=32 -march=mips32r2 -c
> xry111@gcc230:~$ cc b.c -mabi=32 -march=mips64r2 -c
> xry111@gcc230:~$ cc a.o b.o
> xry111@gcc230:~$ ./a.out && echo ok
> ok
> xry111@gcc230:~$
> xry111@gcc230:~$ ld -version
> GNU ld (GNU Binutils for Debian) 2.31.1
> Copyright (C) 2018 Free Software Foundation, Inc.
> This program is free software; you may redistribute it under the terms of
> the GNU General Public License version 3 or (at your option) a later version.
> This program has absolutely no warranty.
>
> So I'd consider the issue a GNU ld regression if it suddenly stops to
> behave like this.

Sorry, I made a mistake: r2 works well while r6 does not.
root@bookworm-mips64r6el:~# gcc -mabi=32 -mips64r6 -O3 -c yy.c
root@bookworm-mips64r6el:~# gcc -mabi=32 -mips32r6 -O3 -c xx.c
root@bookworm-mips64r6el:~# gcc -shared -o xx.so yy.o xx.o
/usr/bin/ld: yy.o: ABI is incompatible with that of the selected emulation
/usr/bin/ld: failed to merge target specific data of file yy.o
/usr/bin/ld: xx.o: ABI is incompatible with that of the selected emulation
/usr/bin/ld: failed to merge target specific data of file xx.o
collect2: error: ld returned 1 exit status

So, it seems that I need to find what happens in gnu ld for r6.

> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University