1 //=-- BPFMCInstLower.cpp - Convert BPF MachineInstr to an MCInst ------------=//
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 code to lower BPF MachineInstrs to their corresponding
10 // MCInst records.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "BPFMCInstLower.h"
15 #include "llvm/CodeGen/AsmPrinter.h"
16 #include "llvm/CodeGen/MachineBasicBlock.h"
17 #include "llvm/CodeGen/MachineInstr.h"
18 #include "llvm/MC/MCAsmInfo.h"
19 #include "llvm/MC/MCContext.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCInst.h"
22 #include "llvm/Support/ErrorHandling.h"
23 #include "llvm/Support/raw_ostream.h"
24 using namespace llvm;
25 
26 MCSymbol *
27 BPFMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
28   return Printer.getSymbol(MO.getGlobal());
29 }
30 
31 MCSymbol *
32 BPFMCInstLower::GetExternalSymbolSymbol(const MachineOperand &MO) const {
33   return Printer.GetExternalSymbolSymbol(MO.getSymbolName());
34 }
35 
36 MCOperand BPFMCInstLower::LowerSymbolOperand(const MachineOperand &MO,
37                                              MCSymbol *Sym) const {
38 
39   const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);
40 
41   if (!MO.isJTI() && MO.getOffset())
42     llvm_unreachable("unknown symbol op");
43 
44   return MCOperand::createExpr(Expr);
45 }
46 
47 void BPFMCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
48   OutMI.setOpcode(MI->getOpcode());
49 
50   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
51     const MachineOperand &MO = MI->getOperand(i);
52 
53     MCOperand MCOp;
54     switch (MO.getType()) {
55     default:
56       MI->print(errs());
57       llvm_unreachable("unknown operand type");
58     case MachineOperand::MO_Register:
59       // Ignore all implicit register operands.
60       if (MO.isImplicit())
61         continue;
62       MCOp = MCOperand::createReg(MO.getReg());
63       break;
64     case MachineOperand::MO_Immediate:
65       MCOp = MCOperand::createImm(MO.getImm());
66       break;
67     case MachineOperand::MO_MachineBasicBlock:
68       MCOp = MCOperand::createExpr(
69           MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx));
70       break;
71     case MachineOperand::MO_RegisterMask:
72       continue;
73     case MachineOperand::MO_ExternalSymbol:
74       MCOp = LowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
75       break;
76     case MachineOperand::MO_GlobalAddress:
77       MCOp = LowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
78       break;
79     }
80 
81     OutMI.addOperand(MCOp);
82   }
83 }
84