llvm/tools/llvm-exegesis/lib/SnippetGenerator.h

   1 //===-- SnippetGenerator.h --------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// Defines the abstract SnippetGenerator class for generating code that allows
  11 /// measuring a certain property of instructions (e.g. latency).
  12 ///
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
  16 #define LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
  17
  18 #include "Assembler.h"
  19 #include "BenchmarkCode.h"
  20 #include "CodeTemplate.h"
  21 #include "LlvmState.h"
  22 #include "MCInstrDescView.h"
  23 #include "RegisterAliasing.h"
  24 #include "llvm/ADT/CombinationGenerator.h"
  25 #include "llvm/MC/MCInst.h"
  26 #include "llvm/Support/Error.h"
  27 #include <cstdlib>
  28 #include <memory>
  29 #include <vector>
  30
  31 namespace llvm {
  32 namespace exegesis {
  33
  34 std::vector<CodeTemplate> getSingleton(CodeTemplate &&CT);
  35
  36 // Generates code templates that has a self-dependency.
  37 Expected<std::vector<CodeTemplate>>
  38 generateSelfAliasingCodeTemplates(InstructionTemplate Variant);
  39
  40 // Generates code templates without assignment constraints.
  41 Expected<std::vector<CodeTemplate>>
  42 generateUnconstrainedCodeTemplates(const InstructionTemplate &Variant,
  43                                    StringRef Msg);
  44
  45 // A class representing failures that happened during Benchmark, they are used
  46 // to report informations to the user.
  47 class SnippetGeneratorFailure : public StringError {
  48 public:
  49   SnippetGeneratorFailure(const Twine &S);
  50 };
  51
  52 // Common code for all benchmark modes.
  53 class SnippetGenerator {
  54 public:
  55   struct Options {
  56     unsigned MaxConfigsPerOpcode = 1;
  57   };
  58
  59   explicit SnippetGenerator(const LLVMState &State, const Options &Opts);
  60
  61   virtual ~SnippetGenerator();
  62
  63   // Calls generateCodeTemplate and expands it into one or more BenchmarkCode.
  64   Error generateConfigurations(const InstructionTemplate &Variant,
  65                                std::vector<BenchmarkCode> &Benchmarks,
  66                                const BitVector &ExtraForbiddenRegs) const;
  67
  68   // Given a snippet, computes which registers the setup code needs to define.
  69   std::vector<RegisterValue> computeRegisterInitialValues(
  70       const std::vector<InstructionTemplate> &Snippet) const;
  71
  72 protected:
  73   const LLVMState &State;
  74   const Options Opts;
  75
  76 private:
  77   // API to be implemented by subclasses.
  78   virtual Expected<std::vector<CodeTemplate>>
  79   generateCodeTemplates(InstructionTemplate Variant,
  80                         const BitVector &ForbiddenRegisters) const = 0;
  81 };
  82
  83 // A global Random Number Generator to randomize configurations.
  84 // FIXME: Move random number generation into an object and make it seedable for
  85 // unit tests.
  86 std::mt19937 &randomGenerator();
  87
  88 // Picks a random unsigned integer from 0 to Max (inclusive).
  89 size_t randomIndex(size_t Max);
  90
  91 // Picks a random bit among the bits set in Vector and returns its index.
  92 // Precondition: Vector must have at least one bit set.
  93 size_t randomBit(const BitVector &Vector);
  94
  95 // Picks a random configuration, then selects a random def and a random use from
  96 // it and finally set the selected values in the provided InstructionInstances.
  97 void setRandomAliasing(const AliasingConfigurations &AliasingConfigurations,
  98                        InstructionTemplate &DefIB, InstructionTemplate &UseIB);
  99
 100 // Assigns a Random Value to all Variables in IT that are still Invalid.
 101 // Do not use any of the registers in `ForbiddenRegs`.
 102 Error randomizeUnsetVariables(const LLVMState &State,
 103                               const BitVector &ForbiddenRegs,
 104                               InstructionTemplate &IT);
 105
 106 } // namespace exegesis
 107 } // namespace llvm
 108
 109 #endif // LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H