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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Test taking longer to compile due to inefficiencies in the SSA updater/LCSSA"
href="https://bugs.llvm.org/show_bug.cgi?id=32996">32996</a>
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<th>Summary</th>
<td>Test taking longer to compile due to inefficiencies in the SSA updater/LCSSA
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>douglas_yung@playstation.sony.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=18427" name="attach_18427" title="Testcase rtc.all.c">attachment 18427</a> <a href="attachment.cgi?id=18427&action=edit" title="Testcase rtc.all.c">[details]</a></span>
Testcase rtc.all.c
Attached is an internal test case which has taken longer to compile over time.
Compiling the attached file with -O2 optimization, I observed the following
compile times:
3.9.0: 265.2633 seconds
3.9.1: 249.5256 seconds
4.0.0: 301.4522 seconds
r302743: 337.4302 seconds
In the 3.9.0 compiler, these were the top 5 passes as reported by the time
report:
142.6473 ( 54.1%) 0.2808 ( 34.6%) 142.9281 ( 54.0%) 142.9435 ( 54.0%)
Unroll loops
52.0263 ( 19.7%) 0.0000 ( 0.0%) 52.0263 ( 19.7%) 52.0531 ( 19.7%)
Eliminate PHI nodes for register allocation
15.3661 ( 5.8%) 0.0624 ( 7.7%) 15.4285 ( 5.8%) 15.4032 ( 5.8%)
Induction Variable Users
9.4693 ( 3.6%) 0.0000 ( 0.0%) 9.4693 ( 3.6%) 9.4335 ( 3.6%)
Unroll loops
7.5660 ( 2.9%) 0.0000 ( 0.0%) 7.5660 ( 2.9%) 7.5846 ( 2.9%) Loop
Strength Reduction
In a compiler built from r302743, these were the top 5 passes as reported by
the time report:
134.3013 ( 40.6%) 3.0576 ( 59.4%) 137.3589 ( 40.9%) 137.3615 ( 40.9%)
Unroll loops
58.3444 ( 17.6%) 1.5600 ( 30.3%) 59.9044 ( 17.8%) 59.8715 ( 17.8%)
Unroll loops
31.2470 ( 9.4%) 0.0000 ( 0.0%) 31.2470 ( 9.3%) 31.2537 ( 9.3%)
Eliminate PHI nodes for register allocation
30.6542 ( 9.3%) 0.0156 ( 0.3%) 30.6698 ( 9.1%) 30.6671 ( 9.1%)
Induction Variable Users
19.3753 ( 5.9%) 0.0000 ( 0.0%) 19.3753 ( 5.8%) 19.3686 ( 5.8%)
Branch Probability Basic Block Placement
Since 3.9.0, the compile time has gotten a worse, and it seems to be related to
the SSA updater/LCSSA. It was observed that r275883 which was reverted in
r276064 and then reapplied in r276077 seemed to cause a big jump in the compile
time. This was reported fixed in r278250, however, the impact on the compile
time of this test seemed to be minimal. A further fix was made in r281949, but
that also had a minimal impact on the compile time.</pre>
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