1//===- LiveRegUnits.cpp - Register Unit Set -------------------------------===//
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 file imlements the LiveRegUnits set.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/CodeGen/LiveRegUnits.h"
14
15#include "llvm/CodeGen/MachineBasicBlock.h"
16#include "llvm/CodeGen/MachineFrameInfo.h"
17#include "llvm/CodeGen/MachineFunction.h"
18#include "llvm/CodeGen/MachineInstrBundle.h"
19#include "llvm/CodeGen/MachineOperand.h"
20#include "llvm/CodeGen/MachineRegisterInfo.h"
21#include "llvm/CodeGen/TargetRegisterInfo.h"
22#include "llvm/MC/MCRegisterInfo.h"
23
24using namespace llvm;
25
26void LiveRegUnits::removeRegsNotPreserved(const uint32_t *RegMask) {
27  for (unsigned U = 0, E = TRI->getNumRegUnits(); U != E; ++U) {
28    for (MCRegUnitRootIterator RootReg(U, TRI); RootReg.isValid(); ++RootReg) {
29      if (MachineOperand::clobbersPhysReg(RegMask, *RootReg))
30        Units.reset(U);
31    }
32  }
33}
34
35void LiveRegUnits::addRegsInMask(const uint32_t *RegMask) {
36  for (unsigned U = 0, E = TRI->getNumRegUnits(); U != E; ++U) {
37    for (MCRegUnitRootIterator RootReg(U, TRI); RootReg.isValid(); ++RootReg) {
38      if (MachineOperand::clobbersPhysReg(RegMask, *RootReg))
39        Units.set(U);
40    }
41  }
42}
43
44void LiveRegUnits::stepBackward(const MachineInstr &MI) {
45  // Remove defined registers and regmask kills from the set.
46  for (const MachineOperand &MOP : phys_regs_and_masks(MI)) {
47    if (MOP.isRegMask()) {
48      removeRegsNotPreserved(MOP.getRegMask());
49      continue;
50    }
51
52    if (MOP.isDef())
53      removeReg(MOP.getReg());
54  }
55
56  // Add uses to the set.
57  for (const MachineOperand &MOP : phys_regs_and_masks(MI)) {
58    if (!MOP.isReg() || !MOP.readsReg())
59      continue;
60    addReg(MOP.getReg());
61  }
62}
63
64void LiveRegUnits::accumulate(const MachineInstr &MI) {
65  // Add defs, uses and regmask clobbers to the set.
66  for (const MachineOperand &MOP : phys_regs_and_masks(MI)) {
67    if (MOP.isRegMask()) {
68      addRegsInMask(MOP.getRegMask());
69      continue;
70    }
71    if (!MOP.isDef() && !MOP.readsReg())
72      continue;
73    addReg(MOP.getReg());
74  }
75}
76
77/// Add live-in registers of basic block \p MBB to \p LiveUnits.
78static void addBlockLiveIns(LiveRegUnits &LiveUnits,
79                            const MachineBasicBlock &MBB) {
80  for (const auto &LI : MBB.liveins())
81    LiveUnits.addRegMasked(LI.PhysReg, LI.LaneMask);
82}
83
84/// Adds all callee saved registers to \p LiveUnits.
85static void addCalleeSavedRegs(LiveRegUnits &LiveUnits,
86                               const MachineFunction &MF) {
87  const MachineRegisterInfo &MRI = MF.getRegInfo();
88  for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; ++CSR)
89    LiveUnits.addReg(*CSR);
90}
91
92void LiveRegUnits::addPristines(const MachineFunction &MF) {
93  const MachineFrameInfo &MFI = MF.getFrameInfo();
94  if (!MFI.isCalleeSavedInfoValid())
95    return;
96  /// This function will usually be called on an empty object, handle this
97  /// as a special case.
98  if (empty()) {
99    /// Add all callee saved regs, then remove the ones that are saved and
100    /// restored.
101    addCalleeSavedRegs(*this, MF);
102    /// Remove the ones that are not saved/restored; they are pristine.
103    for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
104      removeReg(Info.getReg());
105    return;
106  }
107  /// If a callee-saved register that is not pristine is already present
108  /// in the set, we should make sure that it stays in it. Precompute the
109  /// set of pristine registers in a separate object.
110  /// Add all callee saved regs, then remove the ones that are saved+restored.
111  LiveRegUnits Pristine(*TRI);
112  addCalleeSavedRegs(Pristine, MF);
113  /// Remove the ones that are not saved/restored; they are pristine.
114  for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
115    Pristine.removeReg(Info.getReg());
116  addUnits(Pristine.getBitVector());
117}
118
119void LiveRegUnits::addLiveOuts(const MachineBasicBlock &MBB) {
120  const MachineFunction &MF = *MBB.getParent();
121
122  addPristines(MF);
123
124  // To get the live-outs we simply merge the live-ins of all successors.
125  for (const MachineBasicBlock *Succ : MBB.successors())
126    addBlockLiveIns(*this, *Succ);
127
128  // For the return block: Add all callee saved registers.
129  if (MBB.isReturnBlock()) {
130    const MachineFrameInfo &MFI = MF.getFrameInfo();
131    if (MFI.isCalleeSavedInfoValid())
132      addCalleeSavedRegs(*this, MF);
133  }
134}
135
136void LiveRegUnits::addLiveIns(const MachineBasicBlock &MBB) {
137  const MachineFunction &MF = *MBB.getParent();
138  addPristines(MF);
139  addBlockLiveIns(*this, MBB);
140}
141