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c5917e5476
Same as r311392 with some fixes for library dependencies. Thanks to Chapuni for helping work those out! Original commit message: This introduces the FuzzMutate library, which provides structured fuzzing for LLVM IR, as described in my EuroLLVM 2017 talk. Most of the basic mutators to inject and delete IR are provided, with support for most basic operations. llvm-svn: 311402
98 lines
3.0 KiB
C++
98 lines
3.0 KiB
C++
//===--- Random.h - Utilities for random sampling -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Utilities for random sampling.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_FUZZMUTATE_RANDOM_H
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#define LLVM_FUZZMUTATE_RANDOM_H
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#include <random>
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#include "llvm/Support/raw_ostream.h"
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namespace llvm {
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/// Return a uniformly distributed random value between \c Min and \c Max
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template <typename T, typename GenT> T uniform(GenT &Gen, T Min, T Max) {
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return std::uniform_int_distribution<T>(Min, Max)(Gen);
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}
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/// Return a uniformly distributed random value of type \c T
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template <typename T, typename GenT> T uniform(GenT &Gen) {
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return uniform<T>(Gen, std::numeric_limits<T>::min(),
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std::numeric_limits<T>::max());
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}
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/// Randomly selects an item by sampling into a set with an unknown number of
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/// elements, which may each be weighted to be more likely choices.
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template <typename T, typename GenT> class ReservoirSampler {
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GenT &RandGen;
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typename std::remove_const<T>::type Selection = {};
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uint64_t TotalWeight = 0;
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public:
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ReservoirSampler(GenT &RandGen) : RandGen(RandGen) {}
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uint64_t totalWeight() const { return TotalWeight; }
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bool isEmpty() const { return TotalWeight == 0; }
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const T &getSelection() const {
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assert(!isEmpty() && "Nothing selected");
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return Selection;
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}
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explicit operator bool() const { return !isEmpty();}
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const T &operator*() const { return getSelection(); }
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/// Sample each item in \c Items with unit weight
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template <typename RangeT> ReservoirSampler &sample(RangeT &&Items) {
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for (auto &I : Items)
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sample(I, 1);
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return *this;
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}
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/// Sample a single item with the given weight.
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ReservoirSampler &sample(const T &Item, uint64_t Weight) {
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if (!Weight)
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// If the weight is zero, do nothing.
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return *this;
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TotalWeight += Weight;
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// Consider switching from the current element to this one.
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if (uniform<uint64_t>(RandGen, 1, TotalWeight) <= Weight)
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Selection = Item;
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return *this;
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}
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};
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template <typename GenT, typename RangeT,
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typename ElT = typename std::remove_reference<
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decltype(*std::begin(std::declval<RangeT>()))>::type>
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ReservoirSampler<ElT, GenT> makeSampler(GenT &RandGen, RangeT &&Items) {
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ReservoirSampler<ElT, GenT> RS(RandGen);
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RS.sample(Items);
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return RS;
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}
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template <typename GenT, typename T>
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ReservoirSampler<T, GenT> makeSampler(GenT &RandGen, const T &Item,
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uint64_t Weight) {
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ReservoirSampler<T, GenT> RS(RandGen);
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RS.sample(Item, Weight);
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return RS;
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}
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template <typename T, typename GenT>
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ReservoirSampler<T, GenT> makeSampler(GenT &RandGen) {
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return ReservoirSampler<T, GenT>(RandGen);
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}
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} // End llvm namespace
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#endif // LLVM_FUZZMUTATE_RANDOM_H
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