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<div class="moz-cite-prefix">On 03/09/2017 12:21 PM, Steven Perron
wrote:<br>
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<div dir="ltr">I could make something like Daniel's suggestion
work. The main question I still have is how we tell the
difference between the "old-style" DAG and the "new-style"
DAG? I don't know if there is some standard way of doing
this. Do we just base it on the version of llvm-ir?</div>
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We don't generally use IR version like that. Either make the format
incompatible so that you can tell them apart, or we'll add a
separate tag type (!tbaa2 or whatever).<br>
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<div dir="ltr"> </div>
<div dir="ltr">Would there be a need to maintain different code
for both type of DAG? If we change clang to generate the
new-style DAG, things will be fine for C/C++. However, will
this force other components that generate llvm-ir to change?</div>
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<div dir="ltr">In general, what kind of backwards compatibility
do we need to keep?</div>
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There are other frontends that generate TBAA, and there might not be
a clear reason to make them change. The existing format is well
defined, it just does not match C/C++ semantics well enough for our
needs. On the other hand, if the new format subsumes the old one, we
might just expect people to migrate. Let's make that decision
separately. Assume for now that we'll have both at the same time and
we'll change what Clang does.<br>
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-Hal<br>
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<div dir="ltr">Later,</div>
<div dir="ltr">Steven Perron</div>
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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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