83eed0a886
Changes include: * CPU check has been broken up into a number of small libraries * BoringSSL option has been removed * Better abseil integration
56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
// Copyright 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <random>
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#include <string>
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#ifndef THIRD_PARTY_CPU_CHECK_AVX_H_
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#define THIRD_PARTY_CPU_CHECK_AVX_H_
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// x86 AVX usage has complicated core power effects. This code tries
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// to provoke some power transitions that don't otherwise happen.
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// While it's at it, it lightly checks results, but that's not the central
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// goal. ToDo: maybe toughen the correctness checking.
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//
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// The power policies are governed by a number of opaque parameters; this code
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// is based on a lot of guesses.
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//
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// Not thread safe.
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class Avx {
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public:
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static bool can_do_avx();
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static bool can_do_avx512f();
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static bool can_do_fma();
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Avx() {}
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// Activate AVX depending on throw of the dice.
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// Returns syndrome if computational error detected, empty string otherwise.
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std::string MaybeGoHot();
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// Does a bit of computing if in a "hot" mode.
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// Returns syndrome if computational error detected, empty string otherwise.
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std::string BurnIfAvxHeavy();
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private:
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constexpr static int kIterations = 5000;
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std::string Avx256(int rounds);
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std::string Avx256FMA(int rounds);
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std::string Avx512(int rounds);
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int level_ = 0;
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std::knuth_b rng_;
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};
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#endif // THIRD_PARTY_CPU_CHECK_AVX_H_
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