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<div class="moz-cite-prefix">On 09/03/2017 08:35 PM, Daniel Berlin
via llvm-commits wrote:<br>
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I believe this follows from the
GetUnderlyingObject and<br>
isIdentifiedObject related logic in
BasicAAResult::aliasCheck.<br>
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And I'm not aware of any transforms in LLVM
today that contradict the<br>
pointer aliasing rules.<br>
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<div>I assume you meant "do the wrong thing here".
Which i still believe is definitely wrong, FWIW,
but i'm too lazy to go searching through bugzilla
some more today, so i'm going to let it go.</div>
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<div>I'll also point out, you didn't read or write anything
in your example.</div>
<div>Which is strange to me because the usual semantic is
"allowed to alias, but not allowed to be used to
load/store".</div>
<div>IE if you ask if the two pointers alias, the answer is
yes.</div>
<div>If you ask if a load can touch a given store, the
answer is no.</div>
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<div>Here you are saying the pointer aliasing rules apply
even to unwritten/unread pointers.</div>
<div>That to me, is ... very strange.</div>
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As far as I can tell, LLVM does not support pointer aliasing in the
abstract. All queried memory locations are presumed to belong to
some memory access. We may want to change this at some point.<br>
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-Hal<br>
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<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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