FinalizeISel.cpp revision 360784 
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/MachineFunction.h"
18#include "llvm/CodeGen/MachineFunctionPass.h"
19#include "llvm/CodeGen/Passes.h"
20#include "llvm/CodeGen/TargetLowering.h"
21#include "llvm/CodeGen/TargetSubtargetInfo.h"
22#include "llvm/InitializePasses.h"
23#include "llvm/Support/Debug.h"
24using namespace llvm;
25
26#define DEBUG_TYPE "finalize-isel"
27
28namespace {
29  class FinalizeISel : public MachineFunctionPass {
30  public:
31    static char ID; // Pass identification, replacement for typeid
32    FinalizeISel() : MachineFunctionPass(ID) {}
33
34  private:
35    bool runOnMachineFunction(MachineFunction &MF) override;
36
37    void getAnalysisUsage(AnalysisUsage &AU) const override {
38      MachineFunctionPass::getAnalysisUsage(AU);
39    }
40  };
41} // end anonymous namespace
42
43char FinalizeISel::ID = 0;
44char &llvm::FinalizeISelID = FinalizeISel::ID;
45INITIALIZE_PASS(FinalizeISel, DEBUG_TYPE,
46                "Finalize ISel and expand pseudo-instructions", false, false)
47
48bool FinalizeISel::runOnMachineFunction(MachineFunction &MF) {
49  bool Changed = false;
50  const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
51
52  // Iterate through each instruction in the function, looking for pseudos.
53  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
54    MachineBasicBlock *MBB = &*I;
55    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
56         MBBI != MBBE; ) {
57      MachineInstr &MI = *MBBI++;
58
59      // If MI is a pseudo, expand it.
60      if (MI.usesCustomInsertionHook()) {
61        Changed = true;
62        MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
63        // The expansion may involve new basic blocks.
64        if (NewMBB != MBB) {
65          MBB = NewMBB;
66          I = NewMBB->getIterator();
67          MBBI = NewMBB->begin();
68          MBBE = NewMBB->end();
69        }
70      }
71    }
72  }
73
74  TLI->finalizeLowering(MF);
75
76  return Changed;
77}
78