llvm/lib/CodeGen/FinalizeISel.cpp

   1 //===-- llvm/CodeGen/FinalizeISel.cpp ---------------------------*- 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 /// This pass expands Pseudo-instructions produced by ISel, fixes register
  10 /// reservations and may do machine frame information adjustments.
  11 /// The pseudo instructions are used to allow the expansion to contain control
  12 /// flow, such as a conditional move implemented with a conditional branch and a
  13 /// phi, or an atomic operation implemented with a loop.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "llvm/CodeGen/FinalizeISel.h"
  18 #include "llvm/CodeGen/MachineFrameInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineFunctionPass.h"
  21 #include "llvm/CodeGen/TargetInstrInfo.h"
  22 #include "llvm/CodeGen/TargetLowering.h"
  23 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  24 #include "llvm/InitializePasses.h"
  25 using namespace llvm;
  26
  27 #define DEBUG_TYPE "finalize-isel"
  28
  29 namespace {
  30   class FinalizeISel : public MachineFunctionPass {
  31   public:
  32     static char ID; // Pass identification, replacement for typeid
  33     FinalizeISel() : MachineFunctionPass(ID) {}
  34
  35   private:
  36     bool runOnMachineFunction(MachineFunction &MF) override;
  37
  38     void getAnalysisUsage(AnalysisUsage &AU) const override {
  39       MachineFunctionPass::getAnalysisUsage(AU);
  40     }
  41   };
  42 } // end anonymous namespace
  43
  44 static std::pair<bool, bool> runImpl(MachineFunction &MF) {
  45   bool Changed = false;
  46   bool PreserveCFG = true;
  47   const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
  48   const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
  49
  50   // Iterate through each instruction in the function, looking for pseudos.
  51   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
  52     MachineBasicBlock *MBB = &*I;
  53     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
  54          MBBI != MBBE; ) {
  55       MachineInstr &MI = *MBBI++;
  56
  57       // Set AdjustsStack to true if the instruction selector emits a stack
  58       // frame setup instruction or a stack aligning inlineasm.
  59       if (TII->isFrameInstr(MI) || MI.isStackAligningInlineAsm())
  60         MF.getFrameInfo().setAdjustsStack(true);
  61
  62       // If MI is a pseudo, expand it.
  63       if (MI.usesCustomInsertionHook()) {
  64         Changed = true;
  65         MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
  66         // The expansion may involve new basic blocks.
  67         if (NewMBB != MBB) {
  68           PreserveCFG = false;
  69           MBB = NewMBB;
  70           I = NewMBB->getIterator();
  71           MBBI = NewMBB->begin();
  72           MBBE = NewMBB->end();
  73         }
  74       }
  75     }
  76   }
  77
  78   TLI->finalizeLowering(MF);
  79
  80   return {Changed, PreserveCFG};
  81 }
  82
  83 char FinalizeISel::ID = 0;
  84 char &llvm::FinalizeISelID = FinalizeISel::ID;
  85 INITIALIZE_PASS(FinalizeISel, DEBUG_TYPE,
  86                 "Finalize ISel and expand pseudo-instructions", false, false)
  87
  88 bool FinalizeISel::runOnMachineFunction(MachineFunction &MF) {
  89   return runImpl(MF).first;
  90 }
  91
  92 PreservedAnalyses FinalizeISelPass::run(MachineFunction &MF,
  93                                         MachineFunctionAnalysisManager &) {
  94   auto [Changed, PreserveCFG] = runImpl(MF);
  95   if (!Changed)
  96     return PreservedAnalyses::all();
  97   auto PA = getMachineFunctionPassPreservedAnalyses();
  98   if (PreserveCFG)
  99     PA.preserveSet<CFGAnalyses>();
 100   return PA;
 101 }