[llvm-dev] Meaning of loads/stores marked both atomic and volatile (original) (raw)
Reid Kleckner via llvm-dev llvm-dev at lists.llvm.org
Mon Nov 20 13:31:48 PST 2017
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On Mon, Nov 20, 2017 at 1:22 PM, Paweł Batko <pawel.batko at gmail.com> wrote:
Hi Reid,
On 20 November 2017 at 21:44, Reid Kleckner <rnk at google.com> wrote: > For example, llvm should be able to mem2reg > unescaped atomics because it knows they cannot be modified by other threads, Could you point to some resources that explain what an unescaped atomic is?
I mean a local variable that is _Atomic qualified whose address does not escape the function that allocates it. An unused _Atomic int, for example, can be removed. If it were volatile, the storage and any loads and stores would have to be preserved.
In other words, atomics come with a threading model, semantics, and rules that permit certain transformations. Volatile still acts as an escape hatch to throw that out the window. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171120/03094fd8/attachment.html>
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