llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

//===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file contains a printer that converts from our internal
/// representation of machine-dependent LLVM code to the WebAssembly assembly
/// language.
///
//===----------------------------------------------------------------------===//

#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblyRegisterInfo.h"
#include "WebAssemblySubtarget.h"
#include "InstPrinter/WebAssemblyInstPrinter.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"

#include "llvm/ADT/SmallString.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

#define DEBUG_TYPE "asm-printer"

namespace {

class WebAssemblyAsmPrinter final : public AsmPrinter {
  const WebAssemblyInstrInfo *TII;

public:
  WebAssemblyAsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer)
      : AsmPrinter(TM, std::move(Streamer)), TII(nullptr) {}

private:
  const char *getPassName() const override {
    return "WebAssembly Assembly Printer";
  }

  //===------------------------------------------------------------------===//
  // MachineFunctionPass Implementation.
  //===------------------------------------------------------------------===//

  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AsmPrinter::getAnalysisUsage(AU);
  }

  bool runOnMachineFunction(MachineFunction &MF) override {
    TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
    return AsmPrinter::runOnMachineFunction(MF);
  }

  //===------------------------------------------------------------------===//
  // AsmPrinter Implementation.
  //===------------------------------------------------------------------===//

  void EmitConstantPool() override;
  void EmitFunctionEntryLabel() override;
  void EmitFunctionBodyStart() override;
  void EmitFunctionBodyEnd() override;

  void EmitInstruction(const MachineInstr *MI) override;
};

} // end anonymous namespace

//===----------------------------------------------------------------------===//

// Untyped, lower-case version of the opcode's name matching the names
// WebAssembly opcodes are expected to have. The tablegen names are uppercase
// and suffixed with their type (after an underscore).
static SmallString<32> Name(const WebAssemblyInstrInfo *TII,
                            const MachineInstr *MI) {
  std::string N(StringRef(TII->getName(MI->getOpcode())).lower());
  std::string::size_type End = N.rfind('_');
  End = std::string::npos == End ? N.length() : End;
  return SmallString<32>(&N[0], &N[End]);
}

static std::string toSymbol(StringRef S) { return ("$" + S).str(); }

static const char *toType(const Type *Ty) {
  switch (Ty->getTypeID()) {
  default: break;
  case Type::FloatTyID:  return "f32";
  case Type::DoubleTyID: return "f64";
  case Type::IntegerTyID:
    switch (Ty->getIntegerBitWidth()) {
    case 32: return "i32";
    case 64: return "i64";
    default: break;
    }
  }
  DEBUG(dbgs() << "Invalid type "; Ty->print(dbgs()); dbgs() << '\n');
  llvm_unreachable("invalid type");
  return "<invalid>";
}

void WebAssemblyAsmPrinter::EmitConstantPool() {
  assert(MF->getConstantPool()->getConstants().empty() &&
         "WebAssembly disables constant pools");
}

void WebAssemblyAsmPrinter::EmitFunctionEntryLabel() {
  SmallString<128> Str;
  raw_svector_ostream OS(Str);

  CurrentFnSym->redefineIfPossible();

  // The function label could have already been emitted if two symbols end up
  // conflicting due to asm renaming.  Detect this and emit an error.
  if (CurrentFnSym->isVariable())
    report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
                       "' is a protected alias");
  if (CurrentFnSym->isDefined())
    report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
                       "' label emitted multiple times to assembly file");

  OS << "(func " << toSymbol(CurrentFnSym->getName());
  OutStreamer->EmitRawText(OS.str());
}

void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
  SmallString<128> Str;
  raw_svector_ostream OS(Str);
  const Function *F = MF->getFunction();
  for (const Argument &A : F->args())
    OS << " (param " << toType(A.getType()) << ')';
  const Type *Rt = F->getReturnType();
  if (!Rt->isVoidTy())
    OS << " (result " << toType(Rt) << ')';
  OS << '\n';
  OutStreamer->EmitRawText(OS.str());
}

void WebAssemblyAsmPrinter::EmitFunctionBodyEnd() {
  SmallString<128> Str;
  raw_svector_ostream OS(Str);
  OS << ") ;; end func " << toSymbol(CurrentFnSym->getName()) << '\n';
  OutStreamer->EmitRawText(OS.str());
}

void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
  DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
  SmallString<128> Str;
  raw_svector_ostream OS(Str);

  unsigned NumDefs = MI->getDesc().getNumDefs();
  assert(NumDefs <= 1 &&
         "Instructions with multiple result values not implemented");

  OS << '\t';

  if (NumDefs != 0) {
    const MachineOperand &MO = MI->getOperand(0);
    unsigned Reg = MO.getReg();
    OS << "(setlocal @" << TargetRegisterInfo::virtReg2Index(Reg) << ' ';
  }

  OS << '(' << Name(TII, MI);
  for (const MachineOperand &MO : MI->uses())
    switch (MO.getType()) {
    default:
      llvm_unreachable("unexpected machine operand type");
    case MachineOperand::MO_Register: {
      if (MO.isImplicit())
        continue;
      unsigned Reg = MO.getReg();
      OS << " @" << TargetRegisterInfo::virtReg2Index(Reg);
    } break;
    case MachineOperand::MO_Immediate: {
      OS << ' ' << MO.getImm();
    } break;
    case MachineOperand::MO_FPImmediate: {
      static const size_t BufBytes = 128;
      char buf[BufBytes];
      APFloat FP = MO.getFPImm()->getValueAPF();
      if (FP.isNaN())
        assert((FP.bitwiseIsEqual(APFloat::getQNaN(FP.getSemantics())) ||
                FP.bitwiseIsEqual(
                    APFloat::getQNaN(FP.getSemantics(), /*Negative=*/true))) &&
               "convertToHexString handles neither SNaN nor NaN payloads");
      // Use C99's hexadecimal floating-point representation.
      auto Written =
          FP.convertToHexString(buf, /*hexDigits=*/0, /*upperCase=*/false,
                                APFloat::rmNearestTiesToEven);
      (void)Written;
      assert(Written != 0);
      assert(Written < BufBytes);
      OS << ' ' << buf;
    } break;
    case MachineOperand::MO_GlobalAddress: {
      OS << ' ' << toSymbol(MO.getGlobal()->getName());
    } break;
    }
  OS << ')';

  if (NumDefs != 0)
    OS << ')';

  OS << '\n';

  OutStreamer->EmitRawText(OS.str());
}

// Force static initialization.
extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
  RegisterAsmPrinter<WebAssemblyAsmPrinter> X(TheWebAssemblyTarget32);
  RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(TheWebAssemblyTarget64);
}