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//===-- SnippetGenerator.h --------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// Defines the abstract SnippetGenerator class for generating code that allows
/// measuring a certain property of instructions (e.g. latency).
#include "Assembler.h"
#include "BenchmarkCode.h"
#include "CodeTemplate.h"
#include "LlvmState.h"
#include "MCInstrDescView.h"
#include "RegisterAliasing.h"
#include "llvm/ADT/CombinationGenerator.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/Error.h"
#include <cstdlib>
#include <memory>
#include <vector>
namespace llvm {
namespace exegesis {
std::vector<CodeTemplate> getSingleton(CodeTemplate &&CT);
// Generates code templates that has a self-dependency.
generateSelfAliasingCodeTemplates(InstructionTemplate Variant,
const BitVector &ForbiddenRegisters);
// Generates code templates without assignment constraints.
generateUnconstrainedCodeTemplates(const InstructionTemplate &Variant,
StringRef Msg);
// A class representing failures that happened during Benchmark, they are used
// to report informations to the user.
class SnippetGeneratorFailure : public StringError {
SnippetGeneratorFailure(const Twine &S);
// Common code for all benchmark modes.
class SnippetGenerator {
struct Options {
unsigned MaxConfigsPerOpcode = 1;
explicit SnippetGenerator(const LLVMState &State, const Options &Opts);
virtual ~SnippetGenerator();
// Calls generateCodeTemplate and expands it into one or more BenchmarkCode.
Error generateConfigurations(const InstructionTemplate &Variant,
std::vector<BenchmarkCode> &Benchmarks,
const BitVector &ExtraForbiddenRegs) const;
// Given a snippet, computes which registers the setup code needs to define.
std::vector<RegisterValue> computeRegisterInitialValues(
const std::vector<InstructionTemplate> &Snippet) const;
const LLVMState &State;
const Options Opts;
// API to be implemented by subclasses.
virtual Expected<std::vector<CodeTemplate>>
generateCodeTemplates(InstructionTemplate Variant,
const BitVector &ForbiddenRegisters) const = 0;
// A global Random Number Generator to randomize configurations.
// FIXME: Move random number generation into an object and make it seedable for
// unit tests.
std::mt19937 &randomGenerator();
// Picks a random unsigned integer from 0 to Max (inclusive).
size_t randomIndex(size_t Max);
// Picks a random bit among the bits set in Vector and returns its index.
// Precondition: Vector must have at least one bit set.
size_t randomBit(const BitVector &Vector);
// Picks a first bit that is common to these two vectors.
std::optional<int> getFirstCommonBit(const BitVector &A, const BitVector &B);
// Picks a random configuration, then selects a random def and a random use from
// it and finally set the selected values in the provided InstructionInstances.
void setRandomAliasing(const AliasingConfigurations &AliasingConfigurations,
InstructionTemplate &DefIB, InstructionTemplate &UseIB);
// Assigns a Random Value to all Variables in IT that are still Invalid.
// Do not use any of the registers in `ForbiddenRegs`.
Error randomizeUnsetVariables(const LLVMState &State,
const BitVector &ForbiddenRegs,
InstructionTemplate &IT);
} // namespace exegesis
} // namespace llvm