1//===-- BPFRegisterInfo.cpp - BPF Register Information ----------*- C++ -*-===//
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// This file contains the BPF implementation of the TargetRegisterInfo class.
10//
11//===----------------------------------------------------------------------===//
12
13#include "BPFRegisterInfo.h"
14#include "BPF.h"
15#include "BPFSubtarget.h"
16#include "llvm/CodeGen/MachineFrameInfo.h"
17#include "llvm/CodeGen/MachineFunction.h"
18#include "llvm/CodeGen/MachineInstrBuilder.h"
19#include "llvm/CodeGen/RegisterScavenging.h"
20#include "llvm/CodeGen/TargetFrameLowering.h"
21#include "llvm/CodeGen/TargetInstrInfo.h"
22#include "llvm/IR/DiagnosticInfo.h"
23#include "llvm/Support/CommandLine.h"
24#include "llvm/Support/ErrorHandling.h"
25
26#define GET_REGINFO_TARGET_DESC
27#include "BPFGenRegisterInfo.inc"
28using namespace llvm;
29
30static cl::opt<int>
31 BPFStackSizeOption("bpf-stack-size",
32 cl::desc("Specify the BPF stack size limit"),
33 cl::init(512));
34
35BPFRegisterInfo::BPFRegisterInfo()
36 : BPFGenRegisterInfo(BPF::R0) {}
37
38const MCPhysReg *
39BPFRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
40 return CSR_SaveList;
41}
42
43BitVector BPFRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
44 BitVector Reserved(getNumRegs());
45 markSuperRegs(Reserved, BPF::W10); // [W|R]10 is read only frame pointer
46 markSuperRegs(Reserved, BPF::W11); // [W|R]11 is pseudo stack pointer
47 return Reserved;
48}
49
50static void WarnSize(int Offset, MachineFunction &MF, DebugLoc& DL)
51{
52 if (Offset <= -BPFStackSizeOption) {
53 const Function &F = MF.getFunction();
54 DiagnosticInfoUnsupported DiagStackSize(
55 F,
56 "Looks like the BPF stack limit is exceeded. "
57 "Please move large on stack variables into BPF per-cpu array map. For "
58 "non-kernel uses, the stack can be increased using -mllvm "
59 "-bpf-stack-size.\n",
60 DL);
61 F.getContext().diagnose(DI: DiagStackSize);
62 }
63}
64
65bool BPFRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
66 int SPAdj, unsigned FIOperandNum,
67 RegScavenger *RS) const {
68 assert(SPAdj == 0 && "Unexpected");
69
70 unsigned i = 0;
71 MachineInstr &MI = *II;
72 MachineBasicBlock &MBB = *MI.getParent();
73 MachineFunction &MF = *MBB.getParent();
74 DebugLoc DL = MI.getDebugLoc();
75
76 if (!DL)
77 /* try harder to get some debug loc */
78 for (auto &I : MBB)
79 if (I.getDebugLoc()) {
80 DL = I.getDebugLoc();
81 break;
82 }
83
84 while (!MI.getOperand(i).isFI()) {
85 ++i;
86 assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
87 }
88
89 Register FrameReg = getFrameRegister(MF);
90 int FrameIndex = MI.getOperand(i).getIndex();
91 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
92
93 if (MI.getOpcode() == BPF::MOV_rr) {
94 int Offset = MF.getFrameInfo().getObjectOffset(ObjectIdx: FrameIndex);
95
96 WarnSize(Offset, MF, DL);
97 MI.getOperand(i).ChangeToRegister(Reg: FrameReg, isDef: false);
98 Register reg = MI.getOperand(i: i - 1).getReg();
99 BuildMI(MBB, ++II, DL, TII.get(BPF::ADD_ri), reg)
100 .addReg(reg)
101 .addImm(Offset);
102 return false;
103 }
104
105 int Offset = MF.getFrameInfo().getObjectOffset(ObjectIdx: FrameIndex) +
106 MI.getOperand(i: i + 1).getImm();
107
108 if (!isInt<32>(x: Offset))
109 llvm_unreachable("bug in frame offset");
110
111 WarnSize(Offset, MF, DL);
112
113 if (MI.getOpcode() == BPF::FI_ri) {
114 // architecture does not really support FI_ri, replace it with
115 // MOV_rr <target_reg>, frame_reg
116 // ADD_ri <target_reg>, imm
117 Register reg = MI.getOperand(i: i - 1).getReg();
118
119 BuildMI(MBB, ++II, DL, TII.get(BPF::MOV_rr), reg)
120 .addReg(FrameReg);
121 BuildMI(MBB, II, DL, TII.get(BPF::ADD_ri), reg)
122 .addReg(reg)
123 .addImm(Offset);
124
125 // Remove FI_ri instruction
126 MI.eraseFromParent();
127 } else {
128 MI.getOperand(i).ChangeToRegister(Reg: FrameReg, isDef: false);
129 MI.getOperand(i: i + 1).ChangeToImmediate(ImmVal: Offset);
130 }
131 return false;
132}
133
134Register BPFRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
135 return BPF::R10;
136}
137

source code of llvm/lib/Target/BPF/BPFRegisterInfo.cpp