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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to LICM-hoist load - AA imprecision?"
href="https://bugs.llvm.org/show_bug.cgi?id=50933">50933</a>
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<th>Summary</th>
<td>Failure to LICM-hoist load - AA imprecision?
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Global Analyses
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>lebedev.ri@gmail.com
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</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>I'm not quite confident there is actually to do on AA's side,
but this struck me as very surprising, so i better ask.
int foo();
int bar();
struct S {
bool cond;
int* data;
void member(int width) const;
};
void S::member(int width) const {
for(int i = 0; i != width; ++i)
data[i] = cond ? foo() : bar();
}
We currently fail to unswitch this loop: <a href="https://godbolt.org/z/f1zavYPs3">https://godbolt.org/z/f1zavYPs3</a>
I was really expecting we would.
It looks like we are failing to proove that `int* S::data` can not alias
with `&(bool S::cond)`: <a href="https://godbolt.org/z/3vbY3e8jz">https://godbolt.org/z/3vbY3e8jz</a>
And thus MSSA thinks it may be invalidated: <a href="https://godbolt.org/z/Yz4draeee">https://godbolt.org/z/Yz4draeee</a>
TBAA says that it's fine: <a href="https://godbolt.org/z/G4M6jEqcx">https://godbolt.org/z/G4M6jEqcx</a>
The obvious example of how we could arrive at that bad situation would be:
<a href="https://godbolt.org/z/bsrca77d1">https://godbolt.org/z/bsrca77d1</a> <- is that UB?
So in short, is my expectation incorrect here, and this can't be done for C++?
If not, where should i dig?</pre>
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