xref: /freebsd/contrib/llvm-project/llvm/lib/CodeGen/LiveRegUnits.cpp (revision 2f513db72b034fd5ef7f080b11be5c711c15186a)
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 (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
47     if (O->isReg()) {
48       if (!O->isDef() || O->isDebug())
49         continue;
50       unsigned Reg = O->getReg();
51       if (!TargetRegisterInfo::isPhysicalRegister(Reg))
52         continue;
53       removeReg(Reg);
54     } else if (O->isRegMask())
55       removeRegsNotPreserved(O->getRegMask());
56   }
57 
58   // Add uses to the set.
59   for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
60     if (!O->isReg() || !O->readsReg() || O->isDebug())
61       continue;
62     unsigned Reg = O->getReg();
63     if (!TargetRegisterInfo::isPhysicalRegister(Reg))
64       continue;
65     addReg(Reg);
66   }
67 }
68 
69 void LiveRegUnits::accumulate(const MachineInstr &MI) {
70   // Add defs, uses and regmask clobbers to the set.
71   for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
72     if (O->isReg()) {
73       unsigned Reg = O->getReg();
74       if (!TargetRegisterInfo::isPhysicalRegister(Reg))
75         continue;
76       if (!O->isDef() && !O->readsReg())
77         continue;
78       addReg(Reg);
79     } else if (O->isRegMask())
80       addRegsInMask(O->getRegMask());
81   }
82 }
83 
84 /// Add live-in registers of basic block \p MBB to \p LiveUnits.
85 static void addBlockLiveIns(LiveRegUnits &LiveUnits,
86                             const MachineBasicBlock &MBB) {
87   for (const auto &LI : MBB.liveins())
88     LiveUnits.addRegMasked(LI.PhysReg, LI.LaneMask);
89 }
90 
91 /// Adds all callee saved registers to \p LiveUnits.
92 static void addCalleeSavedRegs(LiveRegUnits &LiveUnits,
93                                const MachineFunction &MF) {
94   const MachineRegisterInfo &MRI = MF.getRegInfo();
95   for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; ++CSR)
96     LiveUnits.addReg(*CSR);
97 }
98 
99 void LiveRegUnits::addPristines(const MachineFunction &MF) {
100   const MachineFrameInfo &MFI = MF.getFrameInfo();
101   if (!MFI.isCalleeSavedInfoValid())
102     return;
103   /// This function will usually be called on an empty object, handle this
104   /// as a special case.
105   if (empty()) {
106     /// Add all callee saved regs, then remove the ones that are saved and
107     /// restored.
108     addCalleeSavedRegs(*this, MF);
109     /// Remove the ones that are not saved/restored; they are pristine.
110     for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
111       removeReg(Info.getReg());
112     return;
113   }
114   /// If a callee-saved register that is not pristine is already present
115   /// in the set, we should make sure that it stays in it. Precompute the
116   /// set of pristine registers in a separate object.
117   /// Add all callee saved regs, then remove the ones that are saved+restored.
118   LiveRegUnits Pristine(*TRI);
119   addCalleeSavedRegs(Pristine, MF);
120   /// Remove the ones that are not saved/restored; they are pristine.
121   for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
122     Pristine.removeReg(Info.getReg());
123   addUnits(Pristine.getBitVector());
124 }
125 
126 void LiveRegUnits::addLiveOuts(const MachineBasicBlock &MBB) {
127   const MachineFunction &MF = *MBB.getParent();
128 
129   addPristines(MF);
130 
131   // To get the live-outs we simply merge the live-ins of all successors.
132   for (const MachineBasicBlock *Succ : MBB.successors())
133     addBlockLiveIns(*this, *Succ);
134 
135   // For the return block: Add all callee saved registers.
136   if (MBB.isReturnBlock()) {
137     const MachineFrameInfo &MFI = MF.getFrameInfo();
138     if (MFI.isCalleeSavedInfoValid())
139       addCalleeSavedRegs(*this, MF);
140   }
141 }
142 
143 void LiveRegUnits::addLiveIns(const MachineBasicBlock &MBB) {
144   const MachineFunction &MF = *MBB.getParent();
145   addPristines(MF);
146   addBlockLiveIns(*this, MBB);
147 }
148