1 //===-- AVRAsmPrinter.cpp - AVR LLVM assembly writer ----------------------===//
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 a printer that converts from our internal representation
10 // of machine-dependent LLVM code to GAS-format AVR assembly language.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "AVR.h"
15 #include "AVRMCInstLower.h"
16 #include "AVRSubtarget.h"
17 #include "AVRTargetMachine.h"
18 #include "MCTargetDesc/AVRInstPrinter.h"
19 #include "MCTargetDesc/AVRMCExpr.h"
20 #include "TargetInfo/AVRTargetInfo.h"
21 
22 #include "llvm/CodeGen/AsmPrinter.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineModuleInfo.h"
26 #include "llvm/CodeGen/TargetRegisterInfo.h"
27 #include "llvm/CodeGen/TargetSubtargetInfo.h"
28 #include "llvm/IR/Mangler.h"
29 #include "llvm/MC/MCContext.h"
30 #include "llvm/MC/MCInst.h"
31 #include "llvm/MC/MCStreamer.h"
32 #include "llvm/MC/MCSymbol.h"
33 #include "llvm/MC/TargetRegistry.h"
34 #include "llvm/Support/ErrorHandling.h"
35 #include "llvm/Support/raw_ostream.h"
36 
37 #define DEBUG_TYPE "avr-asm-printer"
38 
39 namespace llvm {
40 
41 /// An AVR assembly code printer.
42 class AVRAsmPrinter : public AsmPrinter {
43 public:
44   AVRAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
45       : AsmPrinter(TM, std::move(Streamer)), MRI(*TM.getMCRegisterInfo()) {}
46 
47   StringRef getPassName() const override { return "AVR Assembly Printer"; }
48 
49   void printOperand(const MachineInstr *MI, unsigned OpNo, raw_ostream &O);
50 
51   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
52                        const char *ExtraCode, raw_ostream &O) override;
53 
54   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
55                              const char *ExtraCode, raw_ostream &O) override;
56 
57   void emitInstruction(const MachineInstr *MI) override;
58 
59   const MCExpr *lowerConstant(const Constant *CV) override;
60 
61   void emitXXStructor(const DataLayout &DL, const Constant *CV) override;
62 
63   bool doFinalization(Module &M) override;
64 
65   void emitStartOfAsmFile(Module &M) override;
66 
67 private:
68   const MCRegisterInfo &MRI;
69   bool EmittedStructorSymbolAttrs = false;
70 };
71 
72 void AVRAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
73                                  raw_ostream &O) {
74   const MachineOperand &MO = MI->getOperand(OpNo);
75 
76   switch (MO.getType()) {
77   case MachineOperand::MO_Register:
78     O << AVRInstPrinter::getPrettyRegisterName(MO.getReg(), MRI);
79     break;
80   case MachineOperand::MO_Immediate:
81     O << MO.getImm();
82     break;
83   case MachineOperand::MO_GlobalAddress:
84     O << getSymbol(MO.getGlobal());
85     break;
86   case MachineOperand::MO_ExternalSymbol:
87     O << *GetExternalSymbolSymbol(MO.getSymbolName());
88     break;
89   case MachineOperand::MO_MachineBasicBlock:
90     O << *MO.getMBB()->getSymbol();
91     break;
92   default:
93     llvm_unreachable("Not implemented yet!");
94   }
95 }
96 
97 bool AVRAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
98                                     const char *ExtraCode, raw_ostream &O) {
99   // Default asm printer can only deal with some extra codes,
100   // so try it first.
101   bool Error = AsmPrinter::PrintAsmOperand(MI, OpNum, ExtraCode, O);
102 
103   if (Error && ExtraCode && ExtraCode[0]) {
104     if (ExtraCode[1] != 0)
105       return true; // Unknown modifier.
106 
107     if (ExtraCode[0] >= 'A' && ExtraCode[0] <= 'Z') {
108       const MachineOperand &RegOp = MI->getOperand(OpNum);
109 
110       assert(RegOp.isReg() && "Operand must be a register when you're"
111                               "using 'A'..'Z' operand extracodes.");
112       Register Reg = RegOp.getReg();
113 
114       unsigned ByteNumber = ExtraCode[0] - 'A';
115 
116       unsigned OpFlags = MI->getOperand(OpNum - 1).getImm();
117       unsigned NumOpRegs = InlineAsm::getNumOperandRegisters(OpFlags);
118       (void)NumOpRegs;
119 
120       const AVRSubtarget &STI = MF->getSubtarget<AVRSubtarget>();
121       const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
122 
123       const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(Reg);
124       unsigned BytesPerReg = TRI.getRegSizeInBits(*RC) / 8;
125       assert(BytesPerReg <= 2 && "Only 8 and 16 bit regs are supported.");
126 
127       unsigned RegIdx = ByteNumber / BytesPerReg;
128       assert(RegIdx < NumOpRegs && "Multibyte index out of range.");
129 
130       Reg = MI->getOperand(OpNum + RegIdx).getReg();
131 
132       if (BytesPerReg == 2) {
133         Reg = TRI.getSubReg(Reg, ByteNumber % BytesPerReg ? AVR::sub_hi
134                                                           : AVR::sub_lo);
135       }
136 
137       O << AVRInstPrinter::getPrettyRegisterName(Reg, MRI);
138       return false;
139     }
140   }
141 
142   if (Error)
143     printOperand(MI, OpNum, O);
144 
145   return false;
146 }
147 
148 bool AVRAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
149                                           unsigned OpNum, const char *ExtraCode,
150                                           raw_ostream &O) {
151   if (ExtraCode && ExtraCode[0])
152     return true; // Unknown modifier
153 
154   const MachineOperand &MO = MI->getOperand(OpNum);
155   (void)MO;
156   assert(MO.isReg() && "Unexpected inline asm memory operand");
157 
158   // TODO: We should be able to look up the alternative name for
159   // the register if it's given.
160   // TableGen doesn't expose a way of getting retrieving names
161   // for registers.
162   if (MI->getOperand(OpNum).getReg() == AVR::R31R30) {
163     O << "Z";
164   } else {
165     assert(MI->getOperand(OpNum).getReg() == AVR::R29R28 &&
166            "Wrong register class for memory operand.");
167     O << "Y";
168   }
169 
170   // If NumOpRegs == 2, then we assume it is product of a FrameIndex expansion
171   // and the second operand is an Imm.
172   unsigned OpFlags = MI->getOperand(OpNum - 1).getImm();
173   unsigned NumOpRegs = InlineAsm::getNumOperandRegisters(OpFlags);
174 
175   if (NumOpRegs == 2) {
176     O << '+' << MI->getOperand(OpNum + 1).getImm();
177   }
178 
179   return false;
180 }
181 
182 void AVRAsmPrinter::emitInstruction(const MachineInstr *MI) {
183   AVRMCInstLower MCInstLowering(OutContext, *this);
184 
185   MCInst I;
186   MCInstLowering.lowerInstruction(*MI, I);
187   EmitToStreamer(*OutStreamer, I);
188 }
189 
190 const MCExpr *AVRAsmPrinter::lowerConstant(const Constant *CV) {
191   MCContext &Ctx = OutContext;
192 
193   if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
194     bool IsProgMem = GV->getAddressSpace() == AVR::ProgramMemory;
195     if (IsProgMem) {
196       const MCExpr *Expr = MCSymbolRefExpr::create(getSymbol(GV), Ctx);
197       return AVRMCExpr::create(AVRMCExpr::VK_AVR_PM, Expr, false, Ctx);
198     }
199   }
200 
201   return AsmPrinter::lowerConstant(CV);
202 }
203 
204 void AVRAsmPrinter::emitXXStructor(const DataLayout &DL, const Constant *CV) {
205   if (!EmittedStructorSymbolAttrs) {
206     OutStreamer->emitRawComment(
207         " Emitting these undefined symbol references causes us to link the"
208         " libgcc code that runs our constructors/destructors");
209     OutStreamer->emitRawComment(" This matches GCC's behavior");
210 
211     MCSymbol *CtorsSym = OutContext.getOrCreateSymbol("__do_global_ctors");
212     OutStreamer->emitSymbolAttribute(CtorsSym, MCSA_Global);
213 
214     MCSymbol *DtorsSym = OutContext.getOrCreateSymbol("__do_global_dtors");
215     OutStreamer->emitSymbolAttribute(DtorsSym, MCSA_Global);
216 
217     EmittedStructorSymbolAttrs = true;
218   }
219 
220   AsmPrinter::emitXXStructor(DL, CV);
221 }
222 
223 bool AVRAsmPrinter::doFinalization(Module &M) {
224   MCSymbol *DoCopyData = OutContext.getOrCreateSymbol("__do_copy_data");
225   MCSymbol *DoClearBss = OutContext.getOrCreateSymbol("__do_clear_bss");
226 
227   // FIXME: We can disable __do_copy_data if there are no static RAM variables.
228 
229   OutStreamer->emitRawComment(
230       " Declaring this symbol tells the CRT that it should");
231   OutStreamer->emitRawComment(
232       "copy all variables from program memory to RAM on startup");
233   OutStreamer->emitSymbolAttribute(DoCopyData, MCSA_Global);
234 
235   OutStreamer->emitRawComment(
236       " Declaring this symbol tells the CRT that it should");
237   OutStreamer->emitRawComment("clear the zeroed data section on startup");
238   OutStreamer->emitSymbolAttribute(DoClearBss, MCSA_Global);
239 
240   return AsmPrinter::doFinalization(M);
241 }
242 
243 void AVRAsmPrinter::emitStartOfAsmFile(Module &M) {
244   const AVRTargetMachine &TM = (const AVRTargetMachine &)MMI->getTarget();
245   const AVRSubtarget *SubTM = (const AVRSubtarget *)TM.getSubtargetImpl();
246   if (!SubTM)
247     return;
248 
249   // Emit __tmp_reg__.
250   OutStreamer->emitAssignment(
251       MMI->getContext().getOrCreateSymbol(StringRef("__tmp_reg__")),
252       MCConstantExpr::create(SubTM->getRegTmpIndex(), MMI->getContext()));
253   // Emit __zero_reg__.
254   OutStreamer->emitAssignment(
255       MMI->getContext().getOrCreateSymbol(StringRef("__zero_reg__")),
256       MCConstantExpr::create(SubTM->getRegZeroIndex(), MMI->getContext()));
257   // Emit __SREG__.
258   OutStreamer->emitAssignment(
259       MMI->getContext().getOrCreateSymbol(StringRef("__SREG__")),
260       MCConstantExpr::create(SubTM->getIORegSREG(), MMI->getContext()));
261   // Emit __SP_H__ if available.
262   if (!SubTM->hasSmallStack())
263     OutStreamer->emitAssignment(
264         MMI->getContext().getOrCreateSymbol(StringRef("__SP_H__")),
265         MCConstantExpr::create(SubTM->getIORegSPH(), MMI->getContext()));
266   // Emit __SP_L__.
267   OutStreamer->emitAssignment(
268       MMI->getContext().getOrCreateSymbol(StringRef("__SP_L__")),
269       MCConstantExpr::create(SubTM->getIORegSPL(), MMI->getContext()));
270   // Emit __EIND__ if available.
271   if (SubTM->hasEIJMPCALL())
272     OutStreamer->emitAssignment(
273         MMI->getContext().getOrCreateSymbol(StringRef("__EIND__")),
274         MCConstantExpr::create(SubTM->getIORegEIND(), MMI->getContext()));
275   // Emit __RAMPZ__ if available.
276   if (SubTM->hasELPM())
277     OutStreamer->emitAssignment(
278         MMI->getContext().getOrCreateSymbol(StringRef("__RAMPZ__")),
279         MCConstantExpr::create(SubTM->getIORegRAMPZ(), MMI->getContext()));
280 }
281 
282 } // end of namespace llvm
283 
284 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRAsmPrinter() {
285   llvm::RegisterAsmPrinter<llvm::AVRAsmPrinter> X(llvm::getTheAVRTarget());
286 }
287