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Groups > linux.kernel > #1403640
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics |
| Date | 2016-05-19 13:00 +0200 |
| Message-ID | <rAtQm-73x-15@gated-at.bofh.it> (permalink) |
| References | <rAdBU-584-21@gated-at.bofh.it> <rAbqp-3On-7@gated-at.bofh.it> <rAbqq-3On-21@gated-at.bofh.it> <rAsUh-6sS-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, May 19, 2016 at 10:52:19AM +0100, David Howells wrote: > Peter Zijlstra <peterz@infradead.org> wrote: > > > Does this generate 'sane' code for LL/SC archs? That is, a single LL/SC > > loop and not a loop around an LL/SC cmpxchg. > I think the code it generates should look something like: > > test_atomic_add_unless: > .L7: > ldaxr w1, [x0] # __atomic_load_n() > cmp w1, 35 # } if (cur == unless) > beq .L4 # } break > add w2, w1, 86 # new = cur + addend > stlxr w4, w2, [x0] > cbnz w4, .L7 > .L4: > mov w1, w0 > ret > > but that requires the compiler to split up the LDAXR and STLXR instructions > and render arbitrary code between. Exactly. > I suspect that might be quite a stretch. > > I've opened: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71191 > > to cover this. Thanks; until such time as this stretch has been made I don't see this intrinsic stuff being much use on any of the LL/SC archs.
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[RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics David Howells <dhowells@redhat.com> - 2016-05-18 17:20 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-18 19:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics David Woodhouse <dwmw2@infradead.org> - 2016-05-19 09:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-19 09:50 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics David Howells <dhowells@redhat.com> - 2016-05-19 12:00 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-19 13:00 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-19 13:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-19 13:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-19 16:30 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-19 16:50 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-19 17:10 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Michael Ellerman <mpe@ellerman.id.au> - 2016-05-20 11:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-05-23 20:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-18 19:40 +0200
Re: [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics Peter Zijlstra <peterz@infradead.org> - 2016-05-18 19:40 +0200
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