lib/CodeGen/TailDuplication.cpp

   1 //===- TailDuplication.cpp - Duplicate blocks into predecessors' tails ----===//
   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 This pass duplicates basic blocks ending in unconditional branches
  10 /// into the tails of their predecessors, using the TailDuplicator utility
  11 /// class.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
  16 #include "llvm/CodeGen/MachineFunction.h"
  17 #include "llvm/CodeGen/MachineFunctionPass.h"
  18 #include "llvm/CodeGen/MachineRegisterInfo.h"
  19 #include "llvm/CodeGen/Passes.h"
  20 #include "llvm/CodeGen/TailDuplicator.h"
  21 #include "llvm/Pass.h"
  22
  23 using namespace llvm;
  24
  25 #define DEBUG_TYPE "tailduplication"
  26
  27 namespace {
  28
  29 class TailDuplicateBase : public MachineFunctionPass {
  30   TailDuplicator Duplicator;
  31   bool PreRegAlloc;
  32 public:
  33   TailDuplicateBase(char &PassID, bool PreRegAlloc)
  34     : MachineFunctionPass(PassID), PreRegAlloc(PreRegAlloc) {}
  35
  36   bool runOnMachineFunction(MachineFunction &MF) override;
  37
  38   void getAnalysisUsage(AnalysisUsage &AU) const override {
  39     AU.addRequired<MachineBranchProbabilityInfo>();
  40     MachineFunctionPass::getAnalysisUsage(AU);
  41   }
  42 };
  43
  44 class TailDuplicate : public TailDuplicateBase {
  45 public:
  46   static char ID;
  47   TailDuplicate() : TailDuplicateBase(ID, false) {
  48     initializeTailDuplicatePass(*PassRegistry::getPassRegistry());
  49   }
  50 };
  51
  52 class EarlyTailDuplicate : public TailDuplicateBase {
  53 public:
  54   static char ID;
  55   EarlyTailDuplicate() : TailDuplicateBase(ID, true) {
  56     initializeEarlyTailDuplicatePass(*PassRegistry::getPassRegistry());
  57   }
  58 };
  59
  60 } // end anonymous namespace
  61
  62 char TailDuplicate::ID;
  63 char EarlyTailDuplicate::ID;
  64
  65 char &llvm::TailDuplicateID = TailDuplicate::ID;
  66 char &llvm::EarlyTailDuplicateID = EarlyTailDuplicate::ID;
  67
  68 INITIALIZE_PASS(TailDuplicate, DEBUG_TYPE, "Tail Duplication", false, false)
  69 INITIALIZE_PASS(EarlyTailDuplicate, "early-tailduplication",
  70                 "Early Tail Duplication", false, false)
  71
  72 bool TailDuplicateBase::runOnMachineFunction(MachineFunction &MF) {
  73   if (skipFunction(MF.getFunction()))
  74     return false;
  75
  76   auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
  77   Duplicator.initMF(MF, PreRegAlloc, MBPI, /*LayoutMode=*/false);
  78
  79   bool MadeChange = false;
  80   while (Duplicator.tailDuplicateBlocks())
  81     MadeChange = true;
  82
  83   return MadeChange;
  84 }