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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - if a loop body contains both a VLA and a call to alloca, we still generate stacksave/stackrestore"
href="http://llvm.org/bugs/show_bug.cgi?id=16099">16099</a>
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<th>Summary</th>
<td>if a loop body contains both a VLA and a call to alloca, we still generate stacksave/stackrestore
</td>
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<th>Product</th>
<td>clang
</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
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
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<th>Reporter</th>
<td>richard-llvm@metafoo.co.uk
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>LLVM miscompiles this code:
_Bool g(int*);
int *h(void*);
int f(int n) {
int *p;
for (int i = 1; i < n; ++i) {
int arr[i];
if (g(arr)) p = h(alloca(i));
}
return *p;
}
We wrap the loop body in @llvm.stacksave() / @llvm.stackrestore() calls, which
nuke both the VLA *and* the alloca. We should warn on this, and presumably also
omit the stacksave/stackrestore in this case. Or hey, maybe compile the VLA to
malloc/free? :)</pre>
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</p>
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