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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InlineCost] Failure to Map a PHI to a Constant"
href="https://bugs.llvm.org/show_bug.cgi?id=34223">34223</a>
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<th>Summary</th>
<td>[InlineCost] Failure to Map a PHI to a Constant
</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>Interprocedural Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>haicheng@codeaurora.org
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>If a callee has IR like this
entry:
switch i32 %arg, label %end.switch [
i32 1, label %sw.bb1
i32 2, label %sw.bb2
......
i32 N, label %sw.bbN
]
sw.bb1: ; preds = %entry
...
sw.bb2: ; preds = %entry
...
...
sw.bbN: ; preds = %entry
...
switch.end: ; preds = %sw.1,
%sw.2,...,%sw.N
%ph = phi i32 [ 1, %sw.bb1 ], [ 2, %sw.bb2 ], ..., [N, %sw.bbN]
The switch condition is a function argument which is a constant from all the
callsites. Then, the phi in switch.end can be mapped to a constant since its
incoming block is known. In my specific test case, the rest of the callee is
relied on %ph and can be proved to be free if %ph can be mapped to a constant.
Currently, InlineCost does not consider the possibility of phi-constant
mapping.</pre>
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</p>
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