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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - New SROA 2x slower on C++ code"
href="http://llvm.org/bugs/show_bug.cgi?id=15471">15471</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>New SROA 2x slower on C++ code
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<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>Core LLVM classes
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nrotem@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>When I compile a large c++ program and compare the old SROA and the new SROA I
notice that the compile time of the new SROA is about 2.2x - 2.5x slower. In
the example below I compiled all of LLVM's InstCombine, ScalarTransfornations
and Utils into a single unoptimzied BC file and ran opt -Os on it. If needed I
can upload the file. I got similar numbers for other large c++ programs. I did
not try C or ObjC.
with use-new-sroa=true.
===-------------------------------------------------------------------------===
... Pass execution timing report ...
===-------------------------------------------------------------------------===
Total Execution Time: 13.9078 seconds (13.8970 wall clock)
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name
---
1.6912 ( 12.7%) 0.0376 ( 6.0%) 1.7287 ( 12.4%) 1.7278 ( 12.4%) Function
Integration/Inlining
1.4309 ( 10.8%) 0.0309 ( 4.9%) 1.4618 ( 10.5%) 1.4610 ( 10.5%) Global
Value Numbering
0.8525 ( 6.4%) 0.0198 ( 3.2%) 0.8723 ( 6.3%) 0.8715 ( 6.3%) Combine
redundant instructions
0.7948 ( 6.0%) 0.0219 ( 3.5%) 0.8167 ( 5.9%) 0.8165 ( 5.9%) Value
Propagation
0.6751 ( 5.1%) 0.0214 ( 3.4%) 0.6965 ( 5.0%) 0.6964 ( 5.0%) Value
Propagation
0.6273 ( 4.7%) 0.0170 ( 2.7%) 0.6444 ( 4.6%) 0.6437 ( 4.6%) Combine
redundant instructions
0.5520 ( 4.2%) 0.0158 ( 2.5%) 0.5678 ( 4.1%) 0.5670 ( 4.1%) Combine
redundant instructions
0.4694 ( 3.5%) 0.0123 ( 2.0%) 0.4817 ( 3.5%) 0.4813 ( 3.5%) Combine
redundant instructions
0.4502 ( 3.4%) 0.0188 ( 3.0%) 0.4690 ( 3.4%) 0.4683 ( 3.4%) SROA
<------------
with use-new-sroa=false.
===-------------------------------------------------------------------------===
... Pass execution timing report ...
===-------------------------------------------------------------------------===
Total Execution Time: 13.4713 seconds (13.4602 wall clock)
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name
---
1.6794 ( 13.0%) 0.0287 ( 5.4%) 1.7081 ( 12.7%) 1.7071 ( 12.7%) Function
Integration/Inlining
1.4281 ( 11.0%) 0.0219 ( 4.1%) 1.4500 ( 10.8%) 1.4495 ( 10.8%) Global
Value Numbering
0.8626 ( 6.7%) 0.0149 ( 2.8%) 0.8775 ( 6.5%) 0.8768 ( 6.5%) Combine
redundant instructions
0.7831 ( 6.1%) 0.0141 ( 2.6%) 0.7972 ( 5.9%) 0.7969 ( 5.9%) Value
Propagation
0.6521 ( 5.0%) 0.0141 ( 2.6%) 0.6663 ( 4.9%) 0.6665 ( 5.0%) Value
Propagation
0.6281 ( 4.9%) 0.0135 ( 2.5%) 0.6416 ( 4.8%) 0.6406 ( 4.8%) Combine
redundant instructions
0.5527 ( 4.3%) 0.0127 ( 2.4%) 0.5654 ( 4.2%) 0.5647 ( 4.2%) Combine
redundant instructions
0.4810 ( 3.7%) 0.0126 ( 2.4%) 0.4937 ( 3.7%) 0.4930 ( 3.7%) Combine
redundant instructions
0.4483 ( 3.5%) 0.0114 ( 2.1%) 0.4597 ( 3.4%) 0.4590 ( 3.4%) Combine
redundant instructions
0.3849 ( 3.0%) 0.0056 ( 1.0%) 0.3904 ( 2.9%) 0.3902 ( 2.9%) Loop
Invariant Code Motion
0.3821 ( 3.0%) 0.0059 ( 1.1%) 0.3881 ( 2.9%) 0.3875 ( 2.9%)
Induction Variable Simplification
0.2635 ( 2.0%) 0.0098 ( 1.8%) 0.2733 ( 2.0%) 0.2730 ( 2.0%) Early
CSE
0.2420 ( 1.9%) 0.0093 ( 1.7%) 0.2513 ( 1.9%) 0.2511 ( 1.9%) Dead
Store Elimination
0.2338 ( 1.8%) 0.0093 ( 1.7%) 0.2431 ( 1.8%) 0.2430 ( 1.8%) Jump
Threading
0.2309 ( 1.8%) 0.0104 ( 1.9%) 0.2412 ( 1.8%) 0.2412 ( 1.8%) Bitcode
Writer
0.1951 ( 1.5%) 0.0120 ( 2.2%) 0.2071 ( 1.5%) 0.2068 ( 1.5%) Scalar
Replacement of Aggregates (DT) <------</pre>
</div>
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