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