1 //=-- BPFMCInstLower.cpp - Convert BPF MachineInstr to an MCInst ------------=//
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 code to lower BPF MachineInstrs to their corresponding
11 // MCInst records.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "BPFMCInstLower.h"
16 #include "llvm/CodeGen/AsmPrinter.h"
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/MC/MCAsmInfo.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCInst.h"
23 #include "llvm/Support/raw_ostream.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/ADT/SmallString.h"
26 using namespace llvm;
27 
28 MCSymbol *
GetGlobalAddressSymbol(const MachineOperand & MO) const29 BPFMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
30   return Printer.getSymbol(MO.getGlobal());
31 }
32 
LowerSymbolOperand(const MachineOperand & MO,MCSymbol * Sym) const33 MCOperand BPFMCInstLower::LowerSymbolOperand(const MachineOperand &MO,
34                                              MCSymbol *Sym) const {
35 
36   const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);
37 
38   if (!MO.isJTI() && MO.getOffset())
39     llvm_unreachable("unknown symbol op");
40 
41   return MCOperand::createExpr(Expr);
42 }
43 
Lower(const MachineInstr * MI,MCInst & OutMI) const44 void BPFMCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
45   OutMI.setOpcode(MI->getOpcode());
46 
47   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
48     const MachineOperand &MO = MI->getOperand(i);
49 
50     MCOperand MCOp;
51     switch (MO.getType()) {
52     default:
53       MI->dump();
54       llvm_unreachable("unknown operand type");
55     case MachineOperand::MO_Register:
56       // Ignore all implicit register operands.
57       if (MO.isImplicit())
58         continue;
59       MCOp = MCOperand::createReg(MO.getReg());
60       break;
61     case MachineOperand::MO_Immediate:
62       MCOp = MCOperand::createImm(MO.getImm());
63       break;
64     case MachineOperand::MO_MachineBasicBlock:
65       MCOp = MCOperand::createExpr(
66           MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx));
67       break;
68     case MachineOperand::MO_RegisterMask:
69       continue;
70     case MachineOperand::MO_GlobalAddress:
71       MCOp = LowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
72       break;
73     }
74 
75     OutMI.addOperand(MCOp);
76   }
77 }
78