2015-09-18 17:02:38 +02:00
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/* Benchmark utility functions.
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2019-01-01 01:11:28 +01:00
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Copyright (C) 2015-2019 Free Software Foundation, Inc.
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2015-09-18 17:02:38 +02:00
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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static volatile unsigned int dontoptimize = 0;
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void
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bench_start (void)
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{
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/* This loop should cause CPU to switch to maximal freqency.
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This makes subsequent measurement more accurate. We need a side effect
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to prevent the loop being deleted by compiler.
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This should be enough to cause CPU to speed up and it is simpler than
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running loop for constant time. This is used when user does not have root
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access to set a constant freqency. */
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for (int k = 0; k < START_ITER; k++)
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dontoptimize += 23 * dontoptimize + 2;
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}
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