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:
AVRAsmPrinter(TargetMachine & TM,std::unique_ptr<MCStreamer> Streamer)44   AVRAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
45       : AsmPrinter(TM, std::move(Streamer)), MRI(*TM.getMCRegisterInfo()) {}
46 
getPassName() const47   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 
printOperand(const MachineInstr * MI,unsigned OpNo,raw_ostream & O)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 
PrintAsmOperand(const MachineInstr * MI,unsigned OpNum,const char * ExtraCode,raw_ostream & O)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 
PrintAsmMemoryOperand(const MachineInstr * MI,unsigned OpNum,const char * ExtraCode,raw_ostream & O)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 
emitInstruction(const MachineInstr * MI)182 void AVRAsmPrinter::emitInstruction(const MachineInstr *MI) {
183   // FIXME: Enable feature predicate checks once all the test pass.
184   // AVR_MC::verifyInstructionPredicates(MI->getOpcode(),
185   //                                     getSubtargetInfo().getFeatureBits());
186 
187   AVRMCInstLower MCInstLowering(OutContext, *this);
188 
189   MCInst I;
190   MCInstLowering.lowerInstruction(*MI, I);
191   EmitToStreamer(*OutStreamer, I);
192 }
193 
lowerConstant(const Constant * CV)194 const MCExpr *AVRAsmPrinter::lowerConstant(const Constant *CV) {
195   MCContext &Ctx = OutContext;
196 
197   if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
198     bool IsProgMem = GV->getAddressSpace() == AVR::ProgramMemory;
199     if (IsProgMem) {
200       const MCExpr *Expr = MCSymbolRefExpr::create(getSymbol(GV), Ctx);
201       return AVRMCExpr::create(AVRMCExpr::VK_AVR_PM, Expr, false, Ctx);
202     }
203   }
204 
205   return AsmPrinter::lowerConstant(CV);
206 }
207 
emitXXStructor(const DataLayout & DL,const Constant * CV)208 void AVRAsmPrinter::emitXXStructor(const DataLayout &DL, const Constant *CV) {
209   if (!EmittedStructorSymbolAttrs) {
210     OutStreamer->emitRawComment(
211         " Emitting these undefined symbol references causes us to link the"
212         " libgcc code that runs our constructors/destructors");
213     OutStreamer->emitRawComment(" This matches GCC's behavior");
214 
215     MCSymbol *CtorsSym = OutContext.getOrCreateSymbol("__do_global_ctors");
216     OutStreamer->emitSymbolAttribute(CtorsSym, MCSA_Global);
217 
218     MCSymbol *DtorsSym = OutContext.getOrCreateSymbol("__do_global_dtors");
219     OutStreamer->emitSymbolAttribute(DtorsSym, MCSA_Global);
220 
221     EmittedStructorSymbolAttrs = true;
222   }
223 
224   AsmPrinter::emitXXStructor(DL, CV);
225 }
226 
doFinalization(Module & M)227 bool AVRAsmPrinter::doFinalization(Module &M) {
228   MCSymbol *DoCopyData = OutContext.getOrCreateSymbol("__do_copy_data");
229   MCSymbol *DoClearBss = OutContext.getOrCreateSymbol("__do_clear_bss");
230 
231   // FIXME: We can disable __do_copy_data if there are no static RAM variables.
232 
233   OutStreamer->emitRawComment(
234       " Declaring this symbol tells the CRT that it should");
235   OutStreamer->emitRawComment(
236       "copy all variables from program memory to RAM on startup");
237   OutStreamer->emitSymbolAttribute(DoCopyData, MCSA_Global);
238 
239   OutStreamer->emitRawComment(
240       " Declaring this symbol tells the CRT that it should");
241   OutStreamer->emitRawComment("clear the zeroed data section on startup");
242   OutStreamer->emitSymbolAttribute(DoClearBss, MCSA_Global);
243 
244   return AsmPrinter::doFinalization(M);
245 }
246 
emitStartOfAsmFile(Module & M)247 void AVRAsmPrinter::emitStartOfAsmFile(Module &M) {
248   const AVRTargetMachine &TM = (const AVRTargetMachine &)MMI->getTarget();
249   const AVRSubtarget *SubTM = (const AVRSubtarget *)TM.getSubtargetImpl();
250   if (!SubTM)
251     return;
252 
253   // Emit __tmp_reg__.
254   OutStreamer->emitAssignment(
255       MMI->getContext().getOrCreateSymbol(StringRef("__tmp_reg__")),
256       MCConstantExpr::create(SubTM->getRegTmpIndex(), MMI->getContext()));
257   // Emit __zero_reg__.
258   OutStreamer->emitAssignment(
259       MMI->getContext().getOrCreateSymbol(StringRef("__zero_reg__")),
260       MCConstantExpr::create(SubTM->getRegZeroIndex(), MMI->getContext()));
261   // Emit __SREG__.
262   OutStreamer->emitAssignment(
263       MMI->getContext().getOrCreateSymbol(StringRef("__SREG__")),
264       MCConstantExpr::create(SubTM->getIORegSREG(), MMI->getContext()));
265   // Emit __SP_H__ if available.
266   if (!SubTM->hasSmallStack())
267     OutStreamer->emitAssignment(
268         MMI->getContext().getOrCreateSymbol(StringRef("__SP_H__")),
269         MCConstantExpr::create(SubTM->getIORegSPH(), MMI->getContext()));
270   // Emit __SP_L__.
271   OutStreamer->emitAssignment(
272       MMI->getContext().getOrCreateSymbol(StringRef("__SP_L__")),
273       MCConstantExpr::create(SubTM->getIORegSPL(), MMI->getContext()));
274   // Emit __EIND__ if available.
275   if (SubTM->hasEIJMPCALL())
276     OutStreamer->emitAssignment(
277         MMI->getContext().getOrCreateSymbol(StringRef("__EIND__")),
278         MCConstantExpr::create(SubTM->getIORegEIND(), MMI->getContext()));
279   // Emit __RAMPZ__ if available.
280   if (SubTM->hasELPM())
281     OutStreamer->emitAssignment(
282         MMI->getContext().getOrCreateSymbol(StringRef("__RAMPZ__")),
283         MCConstantExpr::create(SubTM->getIORegRAMPZ(), MMI->getContext()));
284 }
285 
286 } // end of namespace llvm
287 
LLVMInitializeAVRAsmPrinter()288 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRAsmPrinter() {
289   llvm::RegisterAsmPrinter<llvm::AVRAsmPrinter> X(llvm::getTheAVRTarget());
290 }
291