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//===-- Target.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
/// Classes that handle the creation of target-specific objects. This is
/// similar to Target/TargetRegistry.
#include "BenchmarkResult.h"
#include "BenchmarkRunner.h"
#include "Error.h"
#include "LlvmState.h"
#include "PerfHelper.h"
#include "SnippetGenerator.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Error.h"
#include "llvm/TargetParser/Triple.h"
namespace llvm {
namespace exegesis {
extern cl::OptionCategory Options;
extern cl::OptionCategory BenchmarkOptions;
extern cl::OptionCategory AnalysisOptions;
struct PfmCountersInfo {
// An optional name of a performance counter that can be used to measure
// cycles.
const char *CycleCounter;
// An optional name of a performance counter that can be used to measure
// uops.
const char *UopsCounter;
// An IssueCounter specifies how to measure uops issued to specific proc
// resources.
struct IssueCounter {
const char *Counter;
// The name of the ProcResource that this counter measures.
const char *ProcResName;
// An optional list of IssueCounters.
const IssueCounter *IssueCounters;
unsigned NumIssueCounters;
static const PfmCountersInfo Default;
static const PfmCountersInfo Dummy;
struct CpuAndPfmCounters {
const char *CpuName;
const PfmCountersInfo *PCI;
bool operator<(StringRef S) const { return StringRef(CpuName) < S; }
class ExegesisTarget {
explicit ExegesisTarget(ArrayRef<CpuAndPfmCounters> CpuPfmCounters)
: CpuPfmCounters(CpuPfmCounters) {}
// Targets can use this to create target-specific perf counters.
virtual Expected<std::unique_ptr<pfm::Counter>>
createCounter(StringRef CounterName, const LLVMState &State) const;
// Targets can use this to add target-specific passes in assembleToStream();
virtual void addTargetSpecificPasses(PassManagerBase &PM) const {}
// Generates code to move a constant into a the given register.
// Precondition: Value must fit into Reg.
virtual std::vector<MCInst> setRegTo(const MCSubtargetInfo &STI, unsigned Reg,
const APInt &Value) const = 0;
// Returns the register pointing to scratch memory, or 0 if this target
// does not support memory operands. The benchmark function uses the
// default calling convention.
virtual unsigned getScratchMemoryRegister(const Triple &) const { return 0; }
// Fills memory operands with references to the address at [Reg] + Offset.
virtual void fillMemoryOperands(InstructionTemplate &IT, unsigned Reg,
unsigned Offset) const {
"fillMemoryOperands() requires getScratchMemoryRegister() > 0");
// Returns a counter usable as a loop counter.
virtual unsigned getLoopCounterRegister(const Triple &) const { return 0; }
// Adds the code to decrement the loop counter and
virtual void decrementLoopCounterAndJump(MachineBasicBlock &MBB,
MachineBasicBlock &TargetMBB,
const MCInstrInfo &MII) const {
llvm_unreachable("decrementLoopCounterAndBranch() requires "
"getLoopCounterRegister() > 0");
// Returns a list of unavailable registers.
// Targets can use this to prevent some registers to be automatically selected
// for use in snippets.
virtual ArrayRef<unsigned> getUnavailableRegisters() const { return {}; }
// Returns the maximum number of bytes a load/store instruction can access at
// once. This is typically the size of the largest register available on the
// processor. Note that this only used as a hint to generate independant
// load/stores to/from memory, so the exact returned value does not really
// matter as long as it's large enough.
virtual unsigned getMaxMemoryAccessSize() const { return 0; }
// Assigns a random operand of the right type to variable Var.
// The target is responsible for handling any operand starting from
virtual Error randomizeTargetMCOperand(const Instruction &Instr,
const Variable &Var,
MCOperand &AssignedValue,
const BitVector &ForbiddenRegs) const {
return make_error<Failure>(
"targets with target-specific operands should implement this");
// Returns true if this instruction is supported as a back-to-back
// instructions.
// FIXME: Eventually we should discover this dynamically.
virtual bool allowAsBackToBack(const Instruction &Instr) const {
return true;
// For some instructions, it is interesting to measure how it's performance
// characteristics differ depending on it's operands.
// This allows us to produce all the interesting variants.
virtual std::vector<InstructionTemplate>
generateInstructionVariants(const Instruction &Instr,
unsigned MaxConfigsPerOpcode) const {
// By default, we're happy with whatever randomizer will give us.
return {&Instr};
// Checks hardware and software support for current benchmark mode.
// Returns an error if the target host does not have support to run the
// benchmark.
virtual Error checkFeatureSupport() const { return Error::success(); }
// Creates a snippet generator for the given mode.
createSnippetGenerator(Benchmark::ModeE Mode,
const LLVMState &State,
const SnippetGenerator::Options &Opts) const;
// Creates a benchmark runner for the given mode.
Expected<std::unique_ptr<BenchmarkRunner>> createBenchmarkRunner(
Benchmark::ModeE Mode, const LLVMState &State,
BenchmarkPhaseSelectorE BenchmarkPhaseSelector,
Benchmark::ResultAggregationModeE ResultAggMode =
Benchmark::Min) const;
// Returns the ExegesisTarget for the given triple or nullptr if the target
// does not exist.
static const ExegesisTarget *lookup(Triple TT);
// Returns the default (unspecialized) ExegesisTarget.
static const ExegesisTarget &getDefault();
// Registers a target. Not thread safe.
static void registerTarget(ExegesisTarget *T);
virtual ~ExegesisTarget();
// Returns the Pfm counters for the given CPU (or the default if no pfm
// counters are defined for this CPU).
const PfmCountersInfo &getPfmCounters(StringRef CpuName) const;
// Returns dummy Pfm counters which can be used to execute generated snippet
// without access to performance counters.
const PfmCountersInfo &getDummyPfmCounters() const;
// Saves the CPU state that needs to be preserved when running a benchmark,
// and returns and RAII object that restores the state on destruction.
// By default no state is preserved.
struct SavedState {
virtual ~SavedState();
virtual std::unique_ptr<SavedState> withSavedState() const {
return std::make_unique<SavedState>();
virtual bool matchesArch(Triple::ArchType Arch) const = 0;
// Targets can implement their own snippet generators/benchmarks runners by
// implementing these.
std::unique_ptr<SnippetGenerator> virtual createSerialSnippetGenerator(
const LLVMState &State, const SnippetGenerator::Options &Opts) const;
std::unique_ptr<SnippetGenerator> virtual createParallelSnippetGenerator(
const LLVMState &State, const SnippetGenerator::Options &Opts) const;
std::unique_ptr<BenchmarkRunner> virtual createLatencyBenchmarkRunner(
const LLVMState &State, Benchmark::ModeE Mode,
BenchmarkPhaseSelectorE BenchmarkPhaseSelector,
Benchmark::ResultAggregationModeE ResultAggMode) const;
std::unique_ptr<BenchmarkRunner> virtual createUopsBenchmarkRunner(
const LLVMState &State, BenchmarkPhaseSelectorE BenchmarkPhaseSelector,
Benchmark::ResultAggregationModeE ResultAggMode) const;
const ExegesisTarget *Next = nullptr;
const ArrayRef<CpuAndPfmCounters> CpuPfmCounters;
} // namespace exegesis
} // namespace llvm