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

   1 //===-- ParallelSnippetGenerator.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 /// A SnippetGenerator implementation to create parallel instruction snippets.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_TOOLS_LLVM_EXEGESIS_PARALLELSNIPPETGENERATOR_H
  15 #define LLVM_TOOLS_LLVM_EXEGESIS_PARALLELSNIPPETGENERATOR_H
  16
  17 #include "SnippetGenerator.h"
  18
  19 namespace llvm {
  20 namespace exegesis {
  21
  22 class ParallelSnippetGenerator : public SnippetGenerator {
  23 public:
  24   using SnippetGenerator::SnippetGenerator;
  25   ~ParallelSnippetGenerator() override;
  26
  27   Expected<std::vector<CodeTemplate>>
  28   generateCodeTemplates(InstructionTemplate Variant,
  29                         const BitVector &ForbiddenRegisters) const override;
  30
  31   static constexpr const size_t kMinNumDifferentAddresses = 6;
  32
  33 private:
  34   // Instantiates memory operands within a snippet.
  35   // To make computations as parallel as possible, we generate independant
  36   // memory locations for instructions that load and store. If there are less
  37   // than kMinNumDifferentAddresses in the original snippet, we duplicate
  38   // instructions until there are this number of instructions.
  39   // For example, assuming kMinNumDifferentAddresses=5 and
  40   // getMaxMemoryAccessSize()=64, if the original snippet is:
  41   //   mov eax, [memory]
  42   // we might generate:
  43   //   mov eax, [rdi]
  44   //   mov eax, [rdi + 64]
  45   //   mov eax, [rdi + 128]
  46   //   mov eax, [rdi + 192]
  47   //   mov eax, [rdi + 256]
  48   // If the original snippet is:
  49   //   mov eax, [memory]
  50   //   add eax, [memory]
  51   // we might generate:
  52   //   mov eax, [rdi]
  53   //   add eax, [rdi + 64]
  54   //   mov eax, [rdi + 128]
  55   //   add eax, [rdi + 192]
  56   //   mov eax, [rdi + 256]
  57   void instantiateMemoryOperands(
  58       unsigned ScratchSpaceReg,
  59       std::vector<InstructionTemplate> &SnippetTemplate) const;
  60 };
  61
  62 } // namespace exegesis
  63 } // namespace llvm
  64
  65 #endif // LLVM_TOOLS_LLVM_EXEGESIS_PARALLELSNIPPETGENERATOR_H