llvm/lib/Target/AVR/AVRAsmPrinter.cpp

   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/IR/Module.h"
  30 #include "llvm/MC/MCContext.h"
  31 #include "llvm/MC/MCInst.h"
  32 #include "llvm/MC/MCSectionELF.h"
  33 #include "llvm/MC/MCStreamer.h"
  34 #include "llvm/MC/MCSymbol.h"
  35 #include "llvm/MC/TargetRegistry.h"
  36 #include "llvm/Support/ErrorHandling.h"
  37 #include "llvm/Support/raw_ostream.h"
  38 #include "llvm/Target/TargetLoweringObjectFile.h"
  39
  40 #define DEBUG_TYPE "avr-asm-printer"
  41
  42 namespace llvm {
  43
  44 /// An AVR assembly code printer.
  45 class AVRAsmPrinter : public AsmPrinter {
  46 public:
  47   AVRAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
  48       : AsmPrinter(TM, std::move(Streamer)), MRI(*TM.getMCRegisterInfo()) {}
  49
  50   StringRef getPassName() const override { return "AVR Assembly Printer"; }
  51
  52   void printOperand(const MachineInstr *MI, unsigned OpNo, raw_ostream &O);
  53
  54   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
  55                        const char *ExtraCode, raw_ostream &O) override;
  56
  57   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
  58                              const char *ExtraCode, raw_ostream &O) override;
  59
  60   void emitInstruction(const MachineInstr *MI) override;
  61
  62   const MCExpr *lowerConstant(const Constant *CV) override;
  63
  64   void emitXXStructor(const DataLayout &DL, const Constant *CV) override;
  65
  66   bool doFinalization(Module &M) override;
  67
  68   void emitStartOfAsmFile(Module &M) override;
  69
  70 private:
  71   const MCRegisterInfo &MRI;
  72   bool EmittedStructorSymbolAttrs = false;
  73 };
  74
  75 void AVRAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
  76                                  raw_ostream &O) {
  77   const MachineOperand &MO = MI->getOperand(OpNo);
  78
  79   switch (MO.getType()) {
  80   case MachineOperand::MO_Register:
  81     O << AVRInstPrinter::getPrettyRegisterName(MO.getReg(), MRI);
  82     break;
  83   case MachineOperand::MO_Immediate:
  84     O << MO.getImm();
  85     break;
  86   case MachineOperand::MO_GlobalAddress:
  87     O << getSymbol(MO.getGlobal());
  88     break;
  89   case MachineOperand::MO_ExternalSymbol:
  90     O << *GetExternalSymbolSymbol(MO.getSymbolName());
  91     break;
  92   case MachineOperand::MO_MachineBasicBlock:
  93     O << *MO.getMBB()->getSymbol();
  94     break;
  95   default:
  96     llvm_unreachable("Not implemented yet!");
  97   }
  98 }
  99
 100 bool AVRAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
 101                                     const char *ExtraCode, raw_ostream &O) {
 102   // Default asm printer can only deal with some extra codes,
 103   // so try it first.
 104   if (!AsmPrinter::PrintAsmOperand(MI, OpNum, ExtraCode, O))
 105     return false;
 106
 107   const MachineOperand &MO = MI->getOperand(OpNum);
 108
 109   if (ExtraCode && ExtraCode[0]) {
 110     // Unknown extra code.
 111     if (ExtraCode[1] != 0 || ExtraCode[0] < 'A' || ExtraCode[0] > 'Z')
 112       return true;
 113
 114     // Operand must be a register when using 'A' ~ 'Z' extra code.
 115     if (!MO.isReg())
 116       return true;
 117
 118     Register Reg = MO.getReg();
 119
 120     unsigned ByteNumber = ExtraCode[0] - 'A';
 121     const InlineAsm::Flag OpFlags(MI->getOperand(OpNum - 1).getImm());
 122     const unsigned NumOpRegs = OpFlags.getNumOperandRegisters();
 123
 124     const AVRSubtarget &STI = MF->getSubtarget<AVRSubtarget>();
 125     const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
 126
 127     const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(Reg);
 128     unsigned BytesPerReg = TRI.getRegSizeInBits(*RC) / 8;
 129     assert(BytesPerReg <= 2 && "Only 8 and 16 bit regs are supported.");
 130
 131     unsigned RegIdx = ByteNumber / BytesPerReg;
 132     if (RegIdx >= NumOpRegs)
 133       return true;
 134     Reg = MI->getOperand(OpNum + RegIdx).getReg();
 135
 136     if (BytesPerReg == 2) {
 137       Reg = TRI.getSubReg(Reg, (ByteNumber % BytesPerReg) ? AVR::sub_hi
 138                                                           : AVR::sub_lo);
 139     }
 140
 141     O << AVRInstPrinter::getPrettyRegisterName(Reg, MRI);
 142     return false;
 143   }
 144
 145   if (MO.getType() == MachineOperand::MO_GlobalAddress)
 146     PrintSymbolOperand(MO, O); // Print global symbols.
 147   else
 148     printOperand(MI, OpNum, O); // Fallback to ordinary cases.
 149
 150   return false;
 151 }
 152
 153 bool AVRAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 154                                           unsigned OpNum, const char *ExtraCode,
 155                                           raw_ostream &O) {
 156   if (ExtraCode && ExtraCode[0])
 157     return true; // Unknown modifier
 158
 159   const MachineOperand &MO = MI->getOperand(OpNum);
 160   (void)MO;
 161   assert(MO.isReg() && "Unexpected inline asm memory operand");
 162
 163   // TODO: We should be able to look up the alternative name for
 164   // the register if it's given.
 165   // TableGen doesn't expose a way of getting retrieving names
 166   // for registers.
 167   if (MI->getOperand(OpNum).getReg() == AVR::R31R30) {
 168     O << "Z";
 169   } else if (MI->getOperand(OpNum).getReg() == AVR::R29R28) {
 170     O << "Y";
 171   } else if (MI->getOperand(OpNum).getReg() == AVR::R27R26) {
 172     O << "X";
 173   } else {
 174     assert(false && "Wrong register class for memory operand.");
 175   }
 176
 177   // If NumOpRegs == 2, then we assume it is product of a FrameIndex expansion
 178   // and the second operand is an Imm.
 179   const InlineAsm::Flag OpFlags(MI->getOperand(OpNum - 1).getImm());
 180   const unsigned NumOpRegs = OpFlags.getNumOperandRegisters();
 181
 182   if (NumOpRegs == 2) {
 183     assert(MI->getOperand(OpNum).getReg() != AVR::R27R26 &&
 184            "Base register X can not have offset/displacement.");
 185     O << '+' << MI->getOperand(OpNum + 1).getImm();
 186   }
 187
 188   return false;
 189 }
 190
 191 void AVRAsmPrinter::emitInstruction(const MachineInstr *MI) {
 192   AVR_MC::verifyInstructionPredicates(MI->getOpcode(),
 193                                       getSubtargetInfo().getFeatureBits());
 194
 195   AVRMCInstLower MCInstLowering(OutContext, *this);
 196
 197   MCInst I;
 198   MCInstLowering.lowerInstruction(*MI, I);
 199   EmitToStreamer(*OutStreamer, I);
 200 }
 201
 202 const MCExpr *AVRAsmPrinter::lowerConstant(const Constant *CV) {
 203   MCContext &Ctx = OutContext;
 204
 205   if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 206     bool IsProgMem = GV->getAddressSpace() == AVR::ProgramMemory;
 207     if (IsProgMem) {
 208       const MCExpr *Expr = MCSymbolRefExpr::create(getSymbol(GV), Ctx);
 209       return AVRMCExpr::create(AVRMCExpr::VK_AVR_PM, Expr, false, Ctx);
 210     }
 211   }
 212
 213   return AsmPrinter::lowerConstant(CV);
 214 }
 215
 216 void AVRAsmPrinter::emitXXStructor(const DataLayout &DL, const Constant *CV) {
 217   if (!EmittedStructorSymbolAttrs) {
 218     OutStreamer->emitRawComment(
 219         " Emitting these undefined symbol references causes us to link the"
 220         " libgcc code that runs our constructors/destructors");
 221     OutStreamer->emitRawComment(" This matches GCC's behavior");
 222
 223     MCSymbol *CtorsSym = OutContext.getOrCreateSymbol("__do_global_ctors");
 224     OutStreamer->emitSymbolAttribute(CtorsSym, MCSA_Global);
 225
 226     MCSymbol *DtorsSym = OutContext.getOrCreateSymbol("__do_global_dtors");
 227     OutStreamer->emitSymbolAttribute(DtorsSym, MCSA_Global);
 228
 229     EmittedStructorSymbolAttrs = true;
 230   }
 231
 232   AsmPrinter::emitXXStructor(DL, CV);
 233 }
 234
 235 bool AVRAsmPrinter::doFinalization(Module &M) {
 236   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
 237   const AVRTargetMachine &TM = (const AVRTargetMachine &)MMI->getTarget();
 238   const AVRSubtarget *SubTM = (const AVRSubtarget *)TM.getSubtargetImpl();
 239
 240   bool NeedsCopyData = false;
 241   bool NeedsClearBSS = false;
 242   for (const auto &GO : M.globals()) {
 243     if (!GO.hasInitializer() || GO.hasAvailableExternallyLinkage())
 244       // These globals aren't defined in the current object file.
 245       continue;
 246
 247     if (GO.hasCommonLinkage()) {
 248       // COMMON symbols are put in .bss.
 249       NeedsClearBSS = true;
 250       continue;
 251     }
 252
 253     auto *Section = cast<MCSectionELF>(TLOF.SectionForGlobal(&GO, TM));
 254     if (Section->getName().starts_with(".data"))
 255       NeedsCopyData = true;
 256     else if (Section->getName().starts_with(".rodata") && SubTM->hasLPM())
 257       // AVRs that have a separate program memory (that's most AVRs) store
 258       // .rodata sections in RAM.
 259       NeedsCopyData = true;
 260     else if (Section->getName().starts_with(".bss"))
 261       NeedsClearBSS = true;
 262   }
 263
 264   MCSymbol *DoCopyData = OutContext.getOrCreateSymbol("__do_copy_data");
 265   MCSymbol *DoClearBss = OutContext.getOrCreateSymbol("__do_clear_bss");
 266
 267   if (NeedsCopyData) {
 268     OutStreamer->emitRawComment(
 269         " Declaring this symbol tells the CRT that it should");
 270     OutStreamer->emitRawComment(
 271         "copy all variables from program memory to RAM on startup");
 272     OutStreamer->emitSymbolAttribute(DoCopyData, MCSA_Global);
 273   }
 274
 275   if (NeedsClearBSS) {
 276     OutStreamer->emitRawComment(
 277         " Declaring this symbol tells the CRT that it should");
 278     OutStreamer->emitRawComment("clear the zeroed data section on startup");
 279     OutStreamer->emitSymbolAttribute(DoClearBss, MCSA_Global);
 280   }
 281
 282   return AsmPrinter::doFinalization(M);
 283 }
 284
 285 void AVRAsmPrinter::emitStartOfAsmFile(Module &M) {
 286   const AVRTargetMachine &TM = (const AVRTargetMachine &)MMI->getTarget();
 287   const AVRSubtarget *SubTM = (const AVRSubtarget *)TM.getSubtargetImpl();
 288   if (!SubTM)
 289     return;
 290
 291   // Emit __tmp_reg__.
 292   OutStreamer->emitAssignment(
 293       MMI->getContext().getOrCreateSymbol(StringRef("__tmp_reg__")),
 294       MCConstantExpr::create(SubTM->getRegTmpIndex(), MMI->getContext()));
 295   // Emit __zero_reg__.
 296   OutStreamer->emitAssignment(
 297       MMI->getContext().getOrCreateSymbol(StringRef("__zero_reg__")),
 298       MCConstantExpr::create(SubTM->getRegZeroIndex(), MMI->getContext()));
 299   // Emit __SREG__.
 300   OutStreamer->emitAssignment(
 301       MMI->getContext().getOrCreateSymbol(StringRef("__SREG__")),
 302       MCConstantExpr::create(SubTM->getIORegSREG(), MMI->getContext()));
 303   // Emit __SP_H__ if available.
 304   if (!SubTM->hasSmallStack())
 305     OutStreamer->emitAssignment(
 306         MMI->getContext().getOrCreateSymbol(StringRef("__SP_H__")),
 307         MCConstantExpr::create(SubTM->getIORegSPH(), MMI->getContext()));
 308   // Emit __SP_L__.
 309   OutStreamer->emitAssignment(
 310       MMI->getContext().getOrCreateSymbol(StringRef("__SP_L__")),
 311       MCConstantExpr::create(SubTM->getIORegSPL(), MMI->getContext()));
 312   // Emit __EIND__ if available.
 313   if (SubTM->hasEIJMPCALL())
 314     OutStreamer->emitAssignment(
 315         MMI->getContext().getOrCreateSymbol(StringRef("__EIND__")),
 316         MCConstantExpr::create(SubTM->getIORegEIND(), MMI->getContext()));
 317   // Emit __RAMPZ__ if available.
 318   if (SubTM->hasELPM())
 319     OutStreamer->emitAssignment(
 320         MMI->getContext().getOrCreateSymbol(StringRef("__RAMPZ__")),
 321         MCConstantExpr::create(SubTM->getIORegRAMPZ(), MMI->getContext()));
 322 }
 323
 324 } // end of namespace llvm
 325
 326 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRAsmPrinter() {
 327   llvm::RegisterAsmPrinter<llvm::AVRAsmPrinter> X(llvm::getTheAVRTarget());
 328 }