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 
24 using namespace llvm;
25 
26 void 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 
35 void 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 
44 void 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 
64 void 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.
78 static 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.
85 static 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 
92 void 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 
119 void 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 
136 void LiveRegUnits::addLiveIns(const MachineBasicBlock &MBB) {
137   const MachineFunction &MF = *MBB.getParent();
138   addPristines(MF);
139   addBlockLiveIns(*this, MBB);
140 }
141