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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Dead argument elimination does not respect TCK_MustTail attribute"
href="https://llvm.org/bugs/show_bug.cgi?id=27294">27294</a>
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<th>Summary</th>
<td>Dead argument elimination does not respect TCK_MustTail attribute
</td>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>peter@trailofbits.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following function will have its argument eliminated, which ends up
producing malformed code.
; ModuleID = '/tmp/bug.bc'
declare fastcc void @bar(i64)
; Function Attrs: noinline
define private fastcc void @foo(i64) unnamed_addr #0 {
entry:
musttail call fastcc void @bar(i64 999)
ret void
}
define fastcc void @baz(i64) unnamed_addr {
entry:
musttail call fastcc void @foo(i64 %0)
ret void
}
attributes #0 = { noinline }
When optimized with -O1/-O2/-O3 , this produces invalid bitcode because @foo
doesn't use its argument, but this argument must remain in order for the
tail-call to @bar to remain valid.
The following error is reported:
cannot guarantee tail call due to mismatched parameter counts
musttail call fastcc void @bar(i64 999)
LLVM ERROR: Broken function found, compilation aborted!</pre>
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