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