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Re: GCC in-line assembly and the removal of -mcx16

On Tue, 30 May 2017, Andrew Haley wrote:
> But why is it not then in libgcc?  It's not hard to write it in a
> way that will run on all AArch64 systems.

Ah, sorry, I was oblivious to availability of 128-bit LL/SC in AArch64 base ISA.
GCC could use those to successfully expand 128-bit CAS, as it already does for
64-bit and narrower, but at the moment there's no support for ldaxp/stlxp in
GCC (neither for casp, but that's also not a part of the base ISA).

I believe implementing ldaxp/stlxp in the backend and using them to expand
128-bit CAS (and other 128-bit atomics, except for atomic load) would be the
preferable route, not adding explicit assembly implementations to libgcc.

Alexander
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