1 //===-- BPFRegisterInfo.cpp - BPF Register Information ----------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the BPF implementation of the TargetRegisterInfo class.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "BPFRegisterInfo.h"
15 #include "BPF.h"
16 #include "BPFSubtarget.h"
17 #include "llvm/CodeGen/MachineFrameInfo.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineInstrBuilder.h"
20 #include "llvm/CodeGen/RegisterScavenging.h"
21 #include "llvm/CodeGen/TargetFrameLowering.h"
22 #include "llvm/CodeGen/TargetInstrInfo.h"
23 #include "llvm/IR/DiagnosticInfo.h"
24 #include "llvm/Support/ErrorHandling.h"
25
26 #define GET_REGINFO_TARGET_DESC
27 #include "BPFGenRegisterInfo.inc"
28 using namespace llvm;
29
BPFRegisterInfo()30 BPFRegisterInfo::BPFRegisterInfo()
31 : BPFGenRegisterInfo(BPF::R0) {}
32
33 const MCPhysReg *
getCalleeSavedRegs(const MachineFunction * MF) const34 BPFRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
35 return CSR_SaveList;
36 }
37
getReservedRegs(const MachineFunction & MF) const38 BitVector BPFRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
39 BitVector Reserved(getNumRegs());
40 markSuperRegs(Reserved, BPF::W10); // [W|R]10 is read only frame pointer
41 markSuperRegs(Reserved, BPF::W11); // [W|R]11 is pseudo stack pointer
42 return Reserved;
43 }
44
WarnSize(int Offset,MachineFunction & MF,DebugLoc & DL)45 static void WarnSize(int Offset, MachineFunction &MF, DebugLoc& DL)
46 {
47 if (Offset <= -512) {
48 const Function &F = MF.getFunction();
49 DiagnosticInfoUnsupported DiagStackSize(F,
50 "Looks like the BPF stack limit of 512 bytes is exceeded. "
51 "Please move large on stack variables into BPF per-cpu array map.\n",
52 DL);
53 F.getContext().diagnose(DiagStackSize);
54 }
55 }
56
eliminateFrameIndex(MachineBasicBlock::iterator II,int SPAdj,unsigned FIOperandNum,RegScavenger * RS) const57 void BPFRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
58 int SPAdj, unsigned FIOperandNum,
59 RegScavenger *RS) const {
60 assert(SPAdj == 0 && "Unexpected");
61
62 unsigned i = 0;
63 MachineInstr &MI = *II;
64 MachineBasicBlock &MBB = *MI.getParent();
65 MachineFunction &MF = *MBB.getParent();
66 DebugLoc DL = MI.getDebugLoc();
67
68 if (!DL)
69 /* try harder to get some debug loc */
70 for (auto &I : MBB)
71 if (I.getDebugLoc()) {
72 DL = I.getDebugLoc();
73 break;
74 }
75
76 while (!MI.getOperand(i).isFI()) {
77 ++i;
78 assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
79 }
80
81 unsigned FrameReg = getFrameRegister(MF);
82 int FrameIndex = MI.getOperand(i).getIndex();
83 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
84
85 if (MI.getOpcode() == BPF::MOV_rr) {
86 int Offset = MF.getFrameInfo().getObjectOffset(FrameIndex);
87
88 WarnSize(Offset, MF, DL);
89 MI.getOperand(i).ChangeToRegister(FrameReg, false);
90 unsigned reg = MI.getOperand(i - 1).getReg();
91 BuildMI(MBB, ++II, DL, TII.get(BPF::ADD_ri), reg)
92 .addReg(reg)
93 .addImm(Offset);
94 return;
95 }
96
97 int Offset = MF.getFrameInfo().getObjectOffset(FrameIndex) +
98 MI.getOperand(i + 1).getImm();
99
100 if (!isInt<32>(Offset))
101 llvm_unreachable("bug in frame offset");
102
103 WarnSize(Offset, MF, DL);
104
105 if (MI.getOpcode() == BPF::FI_ri) {
106 // architecture does not really support FI_ri, replace it with
107 // MOV_rr <target_reg>, frame_reg
108 // ADD_ri <target_reg>, imm
109 unsigned reg = MI.getOperand(i - 1).getReg();
110
111 BuildMI(MBB, ++II, DL, TII.get(BPF::MOV_rr), reg)
112 .addReg(FrameReg);
113 BuildMI(MBB, II, DL, TII.get(BPF::ADD_ri), reg)
114 .addReg(reg)
115 .addImm(Offset);
116
117 // Remove FI_ri instruction
118 MI.eraseFromParent();
119 } else {
120 MI.getOperand(i).ChangeToRegister(FrameReg, false);
121 MI.getOperand(i + 1).ChangeToImmediate(Offset);
122 }
123 }
124
getFrameRegister(const MachineFunction & MF) const125 unsigned BPFRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
126 return BPF::R10;
127 }
128