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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - PGO for macro expansion code" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23690&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=JX2YyTyuMyVPp6j5yL4m0OA-NBYVPPtYIuS8fZd0b1c&s=Jw39afVYn1TeMnZwnkJUXgI1F8As60A3TfUuPks11gU&e=">23690</a>
</td>
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<th>Summary</th>
<td>PGO for macro expansion code
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>3.5
</td>
</tr>
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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>
</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>tabloid.adroit@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>#define GET_BIT(lll) \
// blah blah
#define G(label1,label2) \
{ \
// decent amount code \
...
while (1) { \
GET_BIT(label2); \
}; \
}
void f() {
if (..)
G('c', 'd');
while ( .. )
G('a','b');
}
(This simplified case is from SPEC2006 401.bzip2 decompress.c)
After perf sampling, a lot of samples that should have landed in G and
GET_BIT is attributed to the two lines that have G expansion.
Discriminator does not work either for this case. However the last
field of DW_TAG_lexical_block ("Unique ID to identify blocks from a
template function") is unique for all instances of scopes in G and
GET_BIT. It will be great to have PGO get better profile of hot and
cold paths inside macros with nontrivial scopes.</pre>
</div>
</p>
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