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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Regression(r347379): __tsan_{read,write}8 are ~10% slower"
href="https://bugs.llvm.org/show_bug.cgi?id=39748">39748</a>
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<th>Summary</th>
<td>Regression(r347379): __tsan_{read,write}8 are ~10% slower
</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
</td>
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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
</td>
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<th>Component</th>
<td>Global Analyses
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>peter@pcc.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<pre>It seems that r347379 has had the effect of making the __tsan_read8 and
__tsan_write8 functions about 10% slower. These functions are performance
critical since they are called on every 64-bit load and store in a
tsan-instrumented function. This was caught by the
sanitizer-x86_64-linux-autoconf bot:
<a href="http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-autoconf/builds/31402/steps/tsan%20analyze/logs/stdio">http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-autoconf/builds/31402/steps/tsan%20analyze/logs/stdio</a>
I can observe the regression on my local machine like this:
$ projects/compiler-rt/lib/tsan/tests/rtl/TsanRtlTest-x86_64-Test
--gtest_also_run_disabled_tests --gtest_filter=DISABLED_BENCH.Mop8*
Note: Google Test filter = DISABLED_BENCH.Mop8*
[==========] Running 3 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 3 tests from DISABLED_BENCH
[ RUN ] DISABLED_BENCH.Mop8
[ OK ] DISABLED_BENCH.Mop8 (74 ms)
[ RUN ] DISABLED_BENCH.Mop8Read
[ OK ] DISABLED_BENCH.Mop8Read (820 ms)
[ RUN ] DISABLED_BENCH.Mop8Write
[ OK ] DISABLED_BENCH.Mop8Write (817 ms)
[----------] 3 tests from DISABLED_BENCH (1711 ms total)
[----------] Global test environment tear-down
[==========] 3 tests from 1 test case ran. (1711 ms total)
[ PASSED ] 3 tests.
$ projects/compiler-rt/lib/tsan/tests/rtl/TsanRtlTest-x86_64-Test1
--gtest_also_run_disabled_tests --gtest_filter=DISABLED_BENCH.Mop8*
Note: Google Test filter = DISABLED_BENCH.Mop8*
[==========] Running 3 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 3 tests from DISABLED_BENCH
[ RUN ] DISABLED_BENCH.Mop8
[ OK ] DISABLED_BENCH.Mop8 (91 ms)
[ RUN ] DISABLED_BENCH.Mop8Read
[ OK ] DISABLED_BENCH.Mop8Read (905 ms)
[ RUN ] DISABLED_BENCH.Mop8Write
[ OK ] DISABLED_BENCH.Mop8Write (889 ms)
[----------] 3 tests from DISABLED_BENCH (1885 ms total)
[----------] Global test environment tear-down
[==========] 3 tests from 1 test case ran. (1885 ms total)
[ PASSED ] 3 tests.
and the timings are reasonably consistent between runs.</pre>
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