tools/llvm-exegesis/lib/SnippetGenerator.h

   1 //===-- SnippetGenerator.h --------------------------------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 ///
  10 /// \file
  11 /// Defines the abstract SnippetGenerator class for generating code that allows
  12 /// measuring a certain property of instructions (e.g. latency).
  13 ///
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
  17 #define LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
  18
  19 #include "Assembler.h"
  20 #include "BenchmarkCode.h"
  21 #include "CodeTemplate.h"
  22 #include "LlvmState.h"
  23 #include "MCInstrDescView.h"
  24 #include "RegisterAliasing.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 llvm::Expected<std::vector<CodeTemplate>>
  38 generateSelfAliasingCodeTemplates(const Instruction &Instr);
  39
  40 // Generates code templates without assignment constraints.
  41 llvm::Expected<std::vector<CodeTemplate>>
  42 generateUnconstrainedCodeTemplates(const Instruction &Instr,
  43                                    llvm::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 llvm::StringError {
  48 public:
  49   SnippetGeneratorFailure(const llvm::Twine &S);
  50 };
  51
  52 // Common code for all benchmark modes.
  53 class SnippetGenerator {
  54 public:
  55   explicit SnippetGenerator(const LLVMState &State);
  56
  57   virtual ~SnippetGenerator();
  58
  59   // Calls generateCodeTemplate and expands it into one or more BenchmarkCode.
  60   llvm::Expected<std::vector<BenchmarkCode>>
  61   generateConfigurations(const Instruction &Instr) const;
  62
  63   // Given a snippet, computes which registers the setup code needs to define.
  64   std::vector<RegisterValue> computeRegisterInitialValues(
  65       const std::vector<InstructionTemplate> &Snippet) const;
  66
  67 protected:
  68   const LLVMState &State;
  69
  70 private:
  71   // API to be implemented by subclasses.
  72   virtual llvm::Expected<std::vector<CodeTemplate>>
  73   generateCodeTemplates(const Instruction &Instr) const = 0;
  74 };
  75
  76 // A global Random Number Generator to randomize configurations.
  77 // FIXME: Move random number generation into an object and make it seedable for
  78 // unit tests.
  79 std::mt19937 &randomGenerator();
  80
  81 // Picks a random bit among the bits set in Vector and returns its index.
  82 // Precondition: Vector must have at least one bit set.
  83 size_t randomBit(const llvm::BitVector &Vector);
  84
  85 // Picks a random configuration, then selects a random def and a random use from
  86 // it and finally set the selected values in the provided InstructionInstances.
  87 void setRandomAliasing(const AliasingConfigurations &AliasingConfigurations,
  88                        InstructionTemplate &DefIB, InstructionTemplate &UseIB);
  89
  90 // Assigns a Random Value to all Variables in IT that are still Invalid.
  91 // Do not use any of the registers in `ForbiddenRegs`.
  92 void randomizeUnsetVariables(const llvm::BitVector &ForbiddenRegs,
  93                              InstructionTemplate &IT);
  94
  95 } // namespace exegesis
  96 } // namespace llvm
  97
  98 #endif // LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H