Re: [PATCH 1/2] PR target/107299: Fix build issue when long double is IEEE 128-bit

[Segher Boessenkool <segher@kernel.crashing.org>]

Hi!

On Fri, Feb 03, 2023 at 12:49:12AM -0500, Michael Meissner wrote:
> This patch updates the IEEE 128-bit types used in libgcc.
> 
> At the moment, we cannot build GCC when the target uses IEEE 128-bit long
> doubles, such as building the compiler for a native Fedora 36 system.  The
> build dies when it is trying to build the _mulkc3.c and _divkc3 modules.
> 
> This patch changes libgcc to use long double for the IEEE 128-bit base type if
> long double is IEEE 128-bit, and it uses _Float128 otherwise.  The built-in
> functions are adjusted to be the correct version based on the IEEE 128-bit base
> type used.

Please make it much clearer (in the code as well as in the commit
message) that this is a workaround for problems elsewhere.  It
complicates already complicated things that should not be all that
complex in the first place :-(

It is not clear to me that this is good to have at all -- it causes new
non-trivial problems after all -- but you say it allows people to at
least bootstrap, in more cases than before.

So with comments like I said above: okay for trunk.  And not okay for
any backports.

Thanks,


Segher