Bug#956418: src:glibc: Please provide optimized builds for ARMv8.1

[Noah Meyerhans <noahm@debian.org>]

On Sat, Apr 11, 2020 at 08:44:29AM +0200, Florian Weimer wrote:
> > Gcc provides two ways to enable support for these instructions at build
> > time.  The simplest, and least disruptive, is to enable -moutline-atomics
> > globally in the arm64 glibc build.
> 
> Shouldn't GCC do this by default, at least for -mtune=generic?

Maybe.  Would you rather pursue that avenue first?

At least if I'm reading the code right (which I may very well not be
doing, being generally unfamiliar with gcc internals), -mtune=generic
enables the equivalent of ARMv8 support:

https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/common/config/aarch64/aarch64-common.c;h=0bddcc8c3e9282a957c5479b4df7f68058093bab;hb=HEAD#l176

https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/aarch64/aarch64-cores.def;h=ea9b98b4b0ad2a578755561bba5b6d5c56115994;hb=HEAD

https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/aarch64/aarch64.h;h=8f08bad3562c4cbe8acdf5891e84f89d23ea6784;hb=HEAD#l226

noah