Bug#996419: gcc-11: Fails to compile the linux kernel on ARM

[Sebastian Andrzej Siewior <sebastian@breakpoint.cc>]

On 2021-10-16 12:17:40 [+0200], Matthias Klose wrote:
> The change is intended; the configure changes are already in GCC 8, but the
> configure options that we used, are now being deprecated upstream.
> 
> Changes: https://gcc.gnu.org/gcc-8/changes.html

I guess you refer to
| The -march and -mcpu options now accept optional extensions…

which describes the syntax. But this is gcc-8 introducing new syntax not
gcc-11 dropping old syntax or so.

> > On gcc-10 it evaluated to "-march=armv7-a".
> > On gcc-11 it evaluates to "-march=armv5t -Wa,-march=armv7-a" leading to
> 
> -march=armv7-a+fp probably should be used. Same in assembler files where armv7-a
> is used as an architecture. I'm not a kernel developer however, so don't know if
> this is the intended approach.

I was asking because `gcc -v' changes from
  --with-arch=armv7-a --with-fpu=vfpv3-d16
to
  --with-arch=armv7-a+fp

and I wasn't sure if this is intended or a side effect. But it may be
mandatory due to the new syntax.

As for the option, I would guess "armv7-a+nofp" since the expectation is
not to clobber any FPU/SIMD registers like in auto-vectorization etc.
But I see Arnd is on Cc: and silently hope he looks into it ;)

Sebastian