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From: David Chisnall <theraven@FreeBSD.org>
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To: Ed Schouten <ed@80386.nl>
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Subject: Re: svn commit: r230201 - head/lib/libc/gen
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On 19 Jan 2012, at 18:09, Ed Schouten wrote:

> In the very nearby future (after I switch SPARC64 and MIPS to
> libcompiler_rt), it should be possible to safely use C11's =
<stdatomic.h>
> on all supported architectures. The C11 interface allows any operation
> to be combined with any type of barrier.
>=20
> Maybe we should simply migrate this code to use <stdatomic.h> then?

Currently, that will give worse code if we use gcc 4.2.1, but (I hope!) =
better code if we use clang.  With GCC, we are implementing =
atomic_thread_fence() as __sync_synchronize(), which is a full barrier, =
and ignoring its argument.  It would probably be worth postponing any =
such migration until:

1) Clang is the default compiler, and
2) The bugs in LLVM that cause the back end to fatal error on any =
nontrivial code using atomics are fixed.

David=