[MC] Implement RV64GC assembly emission

4 files changed, 939 insertions, 0 deletions

diff --git a/backend/lib/AsmPrinter/AsmPrinter.cpp b/backend/lib/AsmPrinter/AsmPrinter.cpp
new file mode 100644
index 0000000..cebd6b8
--- /dev/null
+++ b/backend/lib/AsmPrinter/AsmPrinter.cpp
@@ -0,0 +1,679 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/AsmPrinter.h"
+
+#include "rcc/CodeGen/CompilationUnit.h"
+#include "rcc/CodeGen/GenericConstant.h"
+#include "rcc/CodeGen/GenericOpcodes.h"
+#include "rcc/CodeGen/GlobalObject.h"
+#include "rcc/CodeGen/InstructionDescriptor.h"
+#include "rcc/CodeGen/MachineBasicBlock.h"
+#include "rcc/CodeGen/MachineCFIInfo.h"
+#include "rcc/CodeGen/MachineConstantPool.h"
+#include "rcc/CodeGen/MachineFunction.h"
+#include "rcc/CodeGen/MachineInstr.h"
+#include "rcc/CodeGen/MachineJumpTableInfo.h"
+#include "rcc/CodeGen/MachineMCContext.h"
+#include "rcc/CodeGen/MachineOperand.h"
+#include "rcc/CodeGen/MachineVerifier.h"
+#include "rcc/CodeGen/TargetConstant.h"
+#include "rcc/CodeGen/TargetDescription.h"
+#include "rcc/CodeGen/TargetMCInstLowering.h"
+#include "rcc/MC/MCCFI.h"
+#include "rcc/MC/MCContext.h"
+#include "rcc/MC/MCExpr.h"
+#include "rcc/MC/MCSection.h"
+#include "rcc/MC/MCStreamer.h"
+#include "rcc/MC/MCSymbol.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <utility>
+#include <variant>
+
+namespace rcc {
+namespace {
+
+[[nodiscard]] Expected<mc::MCExprRef> symbolExpression(mc::MCSymbolRef Symbol) {
+  auto Expression = mc::MCExpr::symbol(std::move(Symbol));
+  if (!Expression)
+    return std::unexpected(Expression.error());
+  return *Expression;
+}
+
+[[nodiscard]] Expected<mc::MCExprRef> addConstant(mc::MCExprRef Expression, std::int64_t Addend) {
+  if (Addend == 0)
+    return Expression;
+  auto Result = mc::MCExpr::binary(mc::MCBinaryOperator::Add, std::move(Expression),
+                                   mc::MCExpr::constant(Addend));
+  if (!Result)
+    return std::unexpected(Result.error());
+  return *Result;
+}
+
+[[nodiscard]] Expected<mc::MCExprRef>
+symbolDifference(mc::MCSymbolRef Minuend, mc::MCSymbolRef Subtrahend, std::int64_t Addend) {
+  auto Left = symbolExpression(std::move(Minuend));
+  if (!Left)
+    return std::unexpected(Left.error());
+  auto Right = symbolExpression(std::move(Subtrahend));
+  if (!Right)
+    return std::unexpected(Right.error());
+  auto Difference =
+      mc::MCExpr::binary(mc::MCBinaryOperator::Subtract, std::move(*Left), std::move(*Right));
+  if (!Difference)
+    return std::unexpected(Difference.error());
+  return addConstant(std::move(*Difference), Addend);
+}
+
+[[nodiscard]] Expected<mc::MCCFIInstruction>
+lowerCFIInstruction(const MachineCFIInstruction &Instruction, MachineMCContext &Context) {
+  mc::MCCFIInstruction Result;
+  const auto Register = [&Result](const MachineCFIRegisterRule &Rule) {
+    Result.Operands.push_back(static_cast<std::int64_t>(Rule.Register.value()));
+  };
+  const auto Offset = [&Result](const MachineCFIOffsetRule &Rule) {
+    Result.Operands.push_back(Rule.Offset);
+  };
+  const auto RegisterOffset = [&Result](const MachineCFIRegisterOffsetRule &Rule) {
+    Result.Operands.push_back(static_cast<std::int64_t>(Rule.Register.value()));
+    Result.Operands.push_back(Rule.Offset);
+  };
+
+  switch (Instruction.operation()) {
+  case MachineCFIOperation::SameValue:
+    Result.Operation = mc::MCCFIOperation::SameValue;
+    Register(*Instruction.getIf<MachineCFIRegisterRule>());
+    break;
+  case MachineCFIOperation::RememberState:
+    Result.Operation = mc::MCCFIOperation::RememberState;
+    break;
+  case MachineCFIOperation::RestoreState:
+    Result.Operation = mc::MCCFIOperation::RestoreState;
+    break;
+  case MachineCFIOperation::Offset:
+    Result.Operation = mc::MCCFIOperation::Offset;
+    RegisterOffset(*Instruction.getIf<MachineCFIRegisterOffsetRule>());
+    break;
+  case MachineCFIOperation::DefCFARegister:
+    Result.Operation = mc::MCCFIOperation::DefCFARegister;
+    Register(*Instruction.getIf<MachineCFIRegisterRule>());
+    break;
+  case MachineCFIOperation::DefCFAOffset:
+    Result.Operation = mc::MCCFIOperation::DefCFAOffset;
+    Offset(*Instruction.getIf<MachineCFIOffsetRule>());
+    break;
+  case MachineCFIOperation::DefCFA:
+    Result.Operation = mc::MCCFIOperation::DefCFA;
+    RegisterOffset(*Instruction.getIf<MachineCFIRegisterOffsetRule>());
+    break;
+  case MachineCFIOperation::RelativeOffset:
+    Result.Operation = mc::MCCFIOperation::RelativeOffset;
+    RegisterOffset(*Instruction.getIf<MachineCFIRegisterOffsetRule>());
+    break;
+  case MachineCFIOperation::AdjustCFAOffset:
+    Result.Operation = mc::MCCFIOperation::AdjustCFAOffset;
+    Offset(*Instruction.getIf<MachineCFIOffsetRule>());
+    break;
+  case MachineCFIOperation::Escape:
+    Result.Operation = mc::MCCFIOperation::Escape;
+    Result.Bytes = Instruction.getIf<MachineCFIEscapeRule>()->Bytes;
+    break;
+  case MachineCFIOperation::Restore:
+    Result.Operation = mc::MCCFIOperation::Restore;
+    Register(*Instruction.getIf<MachineCFIRegisterRule>());
+    break;
+  case MachineCFIOperation::Undefined:
+    Result.Operation = mc::MCCFIOperation::Undefined;
+    Register(*Instruction.getIf<MachineCFIRegisterRule>());
+    break;
+  case MachineCFIOperation::Register: {
+    Result.Operation = mc::MCCFIOperation::Register;
+    const auto &Rule = *Instruction.getIf<MachineCFIRegisterRegisterRule>();
+    Result.Operands.push_back(static_cast<std::int64_t>(Rule.Register.value()));
+    Result.Operands.push_back(static_cast<std::int64_t>(Rule.SourceRegister.value()));
+    break;
+  }
+  case MachineCFIOperation::WindowSave:
+    Result.Operation = mc::MCCFIOperation::WindowSave;
+    break;
+  case MachineCFIOperation::NegateReturnAddressState:
+    Result.Operation = mc::MCCFIOperation::NegateReturnAddressState;
+    break;
+  case MachineCFIOperation::NegateReturnAddressStateWithPC:
+    Result.Operation = mc::MCCFIOperation::NegateReturnAddressStateWithPC;
+    break;
+  case MachineCFIOperation::GNUArgsSize:
+    Result.Operation = mc::MCCFIOperation::GNUArgsSize;
+    Offset(*Instruction.getIf<MachineCFIOffsetRule>());
+    break;
+  case MachineCFIOperation::Label: {
+    Result.Operation = mc::MCCFIOperation::Label;
+    auto Symbol = Context.symbol(Instruction.getIf<MachineCFILabelRule>()->Symbol,
+                                 mc::MCSymbolKind::Temporary);
+    if (!Symbol)
+      return std::unexpected(Symbol.error());
+    Result.Symbol = std::move(*Symbol);
+    break;
+  }
+  case MachineCFIOperation::ValueOffset:
+    Result.Operation = mc::MCCFIOperation::ValueOffset;
+    RegisterOffset(*Instruction.getIf<MachineCFIRegisterOffsetRule>());
+    break;
+  case MachineCFIOperation::LLVMDefAddressSpaceCFA:
+  case MachineCFIOperation::LLVMRegisterPair:
+  case MachineCFIOperation::LLVMVectorRegisters:
+  case MachineCFIOperation::LLVMVectorOffset:
+  case MachineCFIOperation::LLVMVectorRegisterMask:
+    return makeUnexpected(ErrorCode::Unsupported,
+                          "assembly emission does not support this LLVM-specific CFI operation");
+  case MachineCFIOperation::Count:
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "machine CFI instruction has an invalid operation");
+  }
+
+  auto Verification = Result.verify();
+  if (!Verification)
+    return std::unexpected(Verification.error());
+  return Result;
+}
+
+[[nodiscard]] Expected<void> emitNamedLabel(const MachineOperand &Operand,
+                                            MachineMCContext &Context, mc::MCStreamer &Streamer) {
+  const auto *SymbolOperand = Operand.getIf<MCSymbolOperand>();
+  if (SymbolOperand == nullptr || SymbolOperand->Offset != 0 || Operand.targetFlags() != 0) {
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "label pseudo requires an unmodified MC symbol operand");
+  }
+  auto Symbol = Context.symbol(SymbolOperand->Name, mc::MCSymbolKind::Temporary);
+  if (!Symbol)
+    return std::unexpected(Symbol.error());
+  return Streamer.emitLabel(std::move(*Symbol));
+}
+
+[[nodiscard]] bool validValueSize(std::uint64_t Size) noexcept {
+  return Size == 1 || Size == 2 || Size == 4 || Size == 8;
+}
+
+[[nodiscard]] Expected<void> emitGlobalAttributes(const GlobalObjectDesc &Object,
+                                                  const mc::MCSymbolRef &Symbol,
+                                                  mc::MCStreamer &Streamer) {
+  switch (Object.Linkage) {
+  case GlobalLinkage::External:
+  case GlobalLinkage::Appending:
+  case GlobalLinkage::Common: {
+    auto Emitted = Streamer.emitSymbolAttribute(Symbol, mc::MCSymbolAttribute::Global);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+    break;
+  }
+  case GlobalLinkage::LinkOnceAny:
+  case GlobalLinkage::LinkOnceODR:
+  case GlobalLinkage::WeakAny:
+  case GlobalLinkage::WeakODR:
+  case GlobalLinkage::ExternalWeak: {
+    auto Emitted = Streamer.emitSymbolAttribute(Symbol, mc::MCSymbolAttribute::Weak);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+    break;
+  }
+  case GlobalLinkage::Internal:
+  case GlobalLinkage::Private: {
+    auto Emitted = Streamer.emitSymbolAttribute(Symbol, mc::MCSymbolAttribute::Local);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+    break;
+  }
+  case GlobalLinkage::AvailableExternally:
+    break;
+  case GlobalLinkage::Count:
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "global object has invalid linkage during assembly emission");
+  }
+
+  if (Object.Visibility == GlobalVisibility::Hidden) {
+    auto Emitted = Streamer.emitSymbolAttribute(Symbol, mc::MCSymbolAttribute::Hidden);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+  } else if (Object.Visibility == GlobalVisibility::Protected) {
+    auto Emitted = Streamer.emitSymbolAttribute(Symbol, mc::MCSymbolAttribute::Protected);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+  }
+  return Streamer.emitSymbolAttribute(Symbol, Object.TLSModel == GlobalTLSModel::None
+                                                  ? mc::MCSymbolAttribute::Object
+                                                  : mc::MCSymbolAttribute::TLSObject);
+}
+
+} // namespace
+
+Expected<void> AsmPrinter::verifyFunction(const MachineFunction &Function) const {
+  const MachineFunctionProperties Required = {
+      MachineFunctionProperty::NoPHIs,
+      MachineFunctionProperty::Legalized,
+      MachineFunctionProperty::RegBankSelected,
+      MachineFunctionProperty::Selected,
+      MachineFunctionProperty::TiedOpsRewritten,
+      MachineFunctionProperty::NoVRegs,
+      MachineFunctionProperty::FrameFinalized,
+      MachineFunctionProperty::NoFrameIndices,
+      MachineFunctionProperty::NoExecutablePseudos,
+  };
+  if (!Function.properties().containsAll(Required)) {
+    const MachineFunctionProperties Missing = Required.missingFrom(Function.properties());
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "assembly emission requires finalized MIR properties: " +
+                              Missing.toString());
+  }
+  if (!Options.VerifyInput)
+    return {};
+  return MachineVerifier::verify(Function, *Target,
+                                 MachineVerifierOptions{.Mode = MachineVerifierMode::Generic,
+                                                        .Stage = PipelineStage::Emission,
+                                                        .VerifyProperties = true});
+}
+
+Expected<void> AsmPrinter::emitCompilationUnit(const CompilationUnit &Unit) {
+  if (UnitEmissionStarted) {
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "a compilation unit can only be emitted once by an AsmPrinter");
+  }
+  UnitEmissionStarted = true;
+
+  auto Initialized = Context->initialize(Unit);
+  if (!Initialized)
+    return std::unexpected(Initialized.error());
+  auto Header = Lowering->emitFileHeader(*Context, *Streamer);
+  if (!Header)
+    return std::unexpected(Header.error());
+
+  auto Globals = emitGlobalObjects(Unit);
+  if (!Globals)
+    return std::unexpected(Globals.error());
+
+  for (std::size_t Index = 0; Index < Unit.functionCount(); ++Index) {
+    const MachineFunction *Function = Unit.functionAt(Index);
+    if (Function == nullptr) {
+      return makeUnexpected(ErrorCode::InternalError,
+                            "compilation unit contains a null function during assembly emission");
+    }
+    auto Emitted = emitFunction(*Function);
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+  }
+
+  auto Trailer = Lowering->emitFileTrailer(*Context, *Streamer);
+  if (!Trailer)
+    return std::unexpected(Trailer.error());
+  auto Finished = Streamer->finish();
+  if (!Finished)
+    return std::unexpected(Finished.error());
+  UnitEmissionFinished = true;
+  return {};
+}
+
+Expected<void> AsmPrinter::emitGlobalObjects(const CompilationUnit &Unit) {
+  for (std::size_t Index = 0; Index < Unit.globalObjectCount(); ++Index) {
+    const GlobalObjectDesc *Object = Unit.globalObjectAt(Index);
+    if (Object == nullptr)
+      return makeUnexpected(ErrorCode::InternalError, "compilation unit contains a null global");
+    if (Object->isDeclaration() || Object->Linkage == GlobalLinkage::AvailableExternally)
+      continue;
+
+    const mc::MCSymbolRef Symbol = Context->globalSymbol(*Object);
+    if (!Symbol)
+      return makeUnexpected(ErrorCode::InternalError, "global object has no MC symbol");
+    auto Attributes = emitGlobalAttributes(*Object, Symbol, *Streamer);
+    if (!Attributes)
+      return std::unexpected(Attributes.error());
+
+    if (Object->Linkage == GlobalLinkage::Common) {
+      auto Name = mc::printMCSymbolName(Symbol->name());
+      if (!Name)
+        return std::unexpected(Name.error());
+      auto Common =
+          Streamer->emitDirective("comm", *Name + "," + std::to_string(Object->Size) + "," +
+                                              std::to_string(Object->Align.bytes()));
+      if (!Common)
+        return std::unexpected(Common.error());
+      continue;
+    }
+
+    auto Description = Lowering->globalSection(*Object, *Context);
+    if (!Description)
+      return std::unexpected(Description.error());
+    auto Section = Context->context().getOrCreateSection(std::move(*Description));
+    if (!Section)
+      return std::unexpected(Section.error());
+    auto Switched = Streamer->switchSection(std::move(*Section));
+    if (!Switched)
+      return std::unexpected(Switched.error());
+    auto Aligned = Streamer->emitAlignment(Object->Align.bytes());
+    if (!Aligned)
+      return std::unexpected(Aligned.error());
+    auto Label = Streamer->emitLabel(Symbol);
+    if (!Label)
+      return std::unexpected(Label.error());
+    if (!Object->Initializer) {
+      return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                            "defined global object has no initializer");
+    }
+    auto Initializer = Lowering->emitGlobalInitializer(*Object->Initializer, *Context, *Streamer);
+    if (!Initializer)
+      return std::unexpected(Initializer.error());
+    auto Size = Streamer->emitSymbolSize(
+        Symbol, mc::MCExpr::constant(static_cast<std::int64_t>(Object->Size)));
+    if (!Size)
+      return std::unexpected(Size.error());
+  }
+  return {};
+}
+
+Expected<void> AsmPrinter::emitFunction(const MachineFunction &Function) {
+  if (UnitEmissionFinished) {
+    return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                          "cannot emit a function after the assembly stream is finalized");
+  }
+  auto Verification = verifyFunction(Function);
+  if (!Verification)
+    return std::unexpected(Verification.error());
+  auto Initialized = Context->initializeFunction(Function);
+  if (!Initialized)
+    return std::unexpected(Initialized.error());
+
+  auto SectionDescription = Lowering->textSection(Function);
+  if (!SectionDescription)
+    return std::unexpected(SectionDescription.error());
+  auto Section = Context->context().getOrCreateSection(std::move(*SectionDescription));
+  if (!Section)
+    return std::unexpected(Section.error());
+  auto Switched = Streamer->switchSection(std::move(*Section));
+  if (!Switched)
+    return std::unexpected(Switched.error());
+
+  const mc::MCSymbolRef FunctionSymbol = Context->functionSymbol(Function);
+  if (!FunctionSymbol) {
+    return makeUnexpected(ErrorCode::InternalError,
+                          "function has no MC symbol after context initialization");
+  }
+  if (Options.EmitFunctionDirectives) {
+    auto Global = Streamer->emitSymbolAttribute(FunctionSymbol, mc::MCSymbolAttribute::Global);
+    if (!Global)
+      return std::unexpected(Global.error());
+    auto Type = Streamer->emitSymbolAttribute(FunctionSymbol, mc::MCSymbolAttribute::Function);
+    if (!Type)
+      return std::unexpected(Type.error());
+  }
+  if (const auto Alignment = Function.attributes().alignment()) {
+    auto Aligned = Streamer->emitAlignment(Alignment->bytes());
+    if (!Aligned)
+      return std::unexpected(Aligned.error());
+  }
+  auto FunctionLabel = Streamer->emitLabel(FunctionSymbol);
+  if (!FunctionLabel)
+    return std::unexpected(FunctionLabel.error());
+  if (Options.EmitCFI) {
+    mc::MCCFIInstruction StartProc;
+    StartProc.Operation = mc::MCCFIOperation::StartProc;
+    auto CFIStart = Streamer->emitCFI(StartProc);
+    if (!CFIStart)
+      return std::unexpected(CFIStart.error());
+  }
+
+  auto Body = emitFunctionBody(Function);
+  if (!Body)
+    return std::unexpected(Body.error());
+  if (Options.EmitCFI) {
+    mc::MCCFIInstruction EndProc;
+    EndProc.Operation = mc::MCCFIOperation::EndProc;
+    auto CFIEnd = Streamer->emitCFI(EndProc);
+    if (!CFIEnd)
+      return std::unexpected(CFIEnd.error());
+  }
+
+  auto EndSymbol = Context->symbol(".Lfunc_end" + std::to_string(Function.stableID().value()),
+                                   mc::MCSymbolKind::Temporary);
+  if (!EndSymbol)
+    return std::unexpected(EndSymbol.error());
+  auto EndLabel = Streamer->emitLabel(*EndSymbol);
+  if (!EndLabel)
+    return std::unexpected(EndLabel.error());
+  if (Options.EmitFunctionDirectives) {
+    auto Size = symbolDifference(*EndSymbol, FunctionSymbol, 0);
+    if (!Size)
+      return std::unexpected(Size.error());
+    auto EmittedSize = Streamer->emitSymbolSize(FunctionSymbol, std::move(*Size));
+    if (!EmittedSize)
+      return std::unexpected(EmittedSize.error());
+  }
+
+  auto Constants = emitConstantPool(Function);
+  if (!Constants)
+    return std::unexpected(Constants.error());
+  return emitJumpTables(Function);
+}
+
+Expected<void> AsmPrinter::emitFunctionBody(const MachineFunction &Function) {
+  for (const MachineBasicBlock *Block = Function.firstBlock(); Block != nullptr;
+       Block = Block->next()) {
+    if (Block->attributes().alignment().bytes() > 1) {
+      auto Aligned = Streamer->emitAlignment(Block->attributes().alignment().bytes());
+      if (!Aligned)
+        return std::unexpected(Aligned.error());
+    }
+    if (Options.EmitBlockLabels) {
+      const mc::MCSymbolRef Symbol = Context->blockSymbol(*Block);
+      if (!Symbol)
+        return makeUnexpected(ErrorCode::InternalError, "machine block has no MC symbol");
+      auto Label = Streamer->emitLabel(Symbol);
+      if (!Label)
+        return std::unexpected(Label.error());
+    }
+
+    for (const MachineInstr *Instruction = Block->firstInstruction(); Instruction != nullptr;
+         Instruction = Instruction->next()) {
+      const InstructionDescriptor *Descriptor =
+          Target->instructionDescriptor(Instruction->opcode());
+      if (Descriptor == nullptr) {
+        return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                              "assembly emission encountered an unknown opcode");
+      }
+      if (Options.EmitInstructionSymbols) {
+        if (const auto SymbolName = Instruction->preInstrSymbol()) {
+          auto Symbol = Context->symbol(std::string(*SymbolName), mc::MCSymbolKind::Temporary);
+          if (!Symbol)
+            return std::unexpected(Symbol.error());
+          auto Label = Streamer->emitLabel(std::move(*Symbol));
+          if (!Label)
+            return std::unexpected(Label.error());
+        }
+      }
+
+      Expected<void> Emitted;
+      if (Instruction->opcode() == opcode(GenericOpcode::CFI_INSTRUCTION)) {
+        const auto *Index = Instruction->operandAt(0) == nullptr
+                                ? nullptr
+                                : Instruction->operandAt(0)->getIf<CFIIndexOperand>();
+        const MachineCFIInstruction *CFI =
+            Index == nullptr ? nullptr : Function.cfiInfo().instruction(Index->Index);
+        if (CFI == nullptr) {
+          return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                                "CFI pseudo references an invalid CFI instruction");
+        }
+        if (Options.EmitCFI) {
+          auto Lowered = lowerCFIInstruction(*CFI, *Context);
+          if (!Lowered)
+            return std::unexpected(Lowered.error());
+          Emitted = Streamer->emitCFI(*Lowered);
+        }
+      } else if (Instruction->opcode() == opcode(GenericOpcode::EH_LABEL) ||
+                 Instruction->opcode() == opcode(GenericOpcode::GC_LABEL) ||
+                 Instruction->opcode() == opcode(GenericOpcode::ANNOTATION_LABEL)) {
+        if (Instruction->operandAt(0) == nullptr) {
+          return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                                "label pseudo has no symbol operand");
+        }
+        Emitted = emitNamedLabel(*Instruction->operandAt(0), *Context, *Streamer);
+      } else if (Descriptor->Flags.has(InstructionFlag::TerminalEmission)) {
+        Emitted = Lowering->emitTerminalInstruction(*Instruction, *Context, *Streamer);
+      } else if (Descriptor->Flags.has(InstructionFlag::Meta)) {
+        Emitted = {};
+      } else if (Descriptor->Flags.has(InstructionFlag::ProducesCode)) {
+        auto Lowered = Lowering->lowerInstruction(*Instruction, *Context);
+        if (!Lowered)
+          return std::unexpected(Lowered.error());
+        Emitted = Streamer->emitInstruction(*Lowered);
+      } else {
+        return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                              "non-meta instruction has no assembly emission behavior");
+      }
+      if (!Emitted)
+        return std::unexpected(Emitted.error());
+
+      if (Options.EmitInstructionSymbols) {
+        if (const auto SymbolName = Instruction->postInstrSymbol()) {
+          auto Symbol = Context->symbol(std::string(*SymbolName), mc::MCSymbolKind::Temporary);
+          if (!Symbol)
+            return std::unexpected(Symbol.error());
+          auto Label = Streamer->emitLabel(std::move(*Symbol));
+          if (!Label)
+            return std::unexpected(Label.error());
+        }
+      }
+    }
+  }
+  return {};
+}
+
+Expected<void> AsmPrinter::emitConstantPool(const MachineFunction &Function) {
+  for (const MachineConstantPoolEntry &Entry : Function.constantPool().entries()) {
+    const MachineConstantPoolEntryDesc *Description = Entry.description();
+    if (Description == nullptr)
+      continue;
+    auto SectionDescription = Lowering->constantPoolSection(Function, Entry);
+    if (!SectionDescription)
+      return std::unexpected(SectionDescription.error());
+    auto Section = Context->context().getOrCreateSection(std::move(*SectionDescription));
+    if (!Section)
+      return std::unexpected(Section.error());
+    auto Switched = Streamer->switchSection(std::move(*Section));
+    if (!Switched)
+      return std::unexpected(Switched.error());
+    auto Aligned = Streamer->emitAlignment(Description->Align.bytes());
+    if (!Aligned)
+      return std::unexpected(Aligned.error());
+
+    const mc::MCSymbolRef Symbol = Context->constantPoolSymbol(Function, Entry.index());
+    if (!Symbol)
+      return makeUnexpected(ErrorCode::InternalError, "constant-pool entry has no MC symbol");
+    auto Label = Streamer->emitLabel(Symbol);
+    if (!Label)
+      return std::unexpected(Label.error());
+
+    Expected<void> Emitted;
+    if (const auto *Generic = std::get_if<GenericConstantData>(&Description->Value)) {
+      Emitted = Lowering->emitGenericConstant(*Generic, Description->Size, *Context, *Streamer);
+    } else if (const auto *TargetValue = std::get_if<TargetConstant>(&Description->Value)) {
+      Emitted = Lowering->emitTargetConstant(*TargetValue, *Context, *Streamer);
+    } else if (const auto *Difference =
+                   std::get_if<SymbolDifferenceConstant>(&Description->Value)) {
+      if (!validValueSize(Description->Size)) {
+        return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                              "symbol-difference constant has an unsupported storage size");
+      }
+      auto Minuend = Context->symbol(Difference->Minuend);
+      if (!Minuend)
+        return std::unexpected(Minuend.error());
+      auto Subtrahend = Context->symbol(Difference->Subtrahend);
+      if (!Subtrahend)
+        return std::unexpected(Subtrahend.error());
+      auto Expression = symbolDifference(*Minuend, *Subtrahend, Difference->Addend);
+      if (!Expression)
+        return std::unexpected(Expression.error());
+      Emitted =
+          Streamer->emitValue(std::move(*Expression), static_cast<std::uint8_t>(Description->Size));
+    } else if (const auto *Address = std::get_if<BlockAddressConstant>(&Description->Value)) {
+      if (!validValueSize(Description->Size)) {
+        return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                              "block-address constant has an unsupported storage size");
+      }
+      auto AddressSymbol = Context->blockAddressSymbol(Address->FunctionName, Address->BlockName);
+      if (!AddressSymbol)
+        return std::unexpected(AddressSymbol.error());
+      auto Expression = symbolExpression(std::move(*AddressSymbol));
+      if (!Expression)
+        return std::unexpected(Expression.error());
+      Expression = addConstant(std::move(*Expression), Address->Addend);
+      if (!Expression)
+        return std::unexpected(Expression.error());
+      Emitted =
+          Streamer->emitValue(std::move(*Expression), static_cast<std::uint8_t>(Description->Size));
+    } else if (const auto *TargetExpression =
+                   std::get_if<TargetExpressionConstant>(&Description->Value)) {
+      Emitted = Lowering->emitTargetConstant(TargetExpression->Expression, *Context, *Streamer);
+    } else {
+      return makeUnexpected(ErrorCode::InternalError, "constant-pool value has an invalid kind");
+    }
+    if (!Emitted)
+      return std::unexpected(Emitted.error());
+  }
+  return {};
+}
+
+Expected<void> AsmPrinter::emitJumpTables(const MachineFunction &Function) {
+  for (const MachineJumpTableEntry &Entry : Function.jumpTableInfo().tables()) {
+    const MachineJumpTableDesc *Description = Entry.description();
+    if (Description == nullptr)
+      continue;
+    auto SectionDescription = Lowering->jumpTableSection(Function, Entry);
+    if (!SectionDescription)
+      return std::unexpected(SectionDescription.error());
+    auto Section = Context->context().getOrCreateSection(std::move(*SectionDescription));
+    if (!Section)
+      return std::unexpected(Section.error());
+    auto Switched = Streamer->switchSection(std::move(*Section));
+    if (!Switched)
+      return std::unexpected(Switched.error());
+    auto Aligned = Streamer->emitAlignment(Description->Align.bytes());
+    if (!Aligned)
+      return std::unexpected(Aligned.error());
+
+    const mc::MCSymbolRef TableSymbol = Context->jumpTableSymbol(Function, Entry.index());
+    if (!TableSymbol)
+      return makeUnexpected(ErrorCode::InternalError, "jump-table entry has no MC symbol");
+    auto Label = Streamer->emitLabel(TableSymbol);
+    if (!Label)
+      return std::unexpected(Label.error());
+
+    if (Description->Encoding != JumpTableEntryEncoding::BlockAddress &&
+        Description->Encoding != JumpTableEntryEncoding::LabelDifference32 &&
+        Description->Encoding != JumpTableEntryEncoding::LabelDifference64) {
+      auto TargetTable = Lowering->emitTargetJumpTable(Function, Entry, *Context, *Streamer);
+      if (!TargetTable)
+        return std::unexpected(TargetTable.error());
+      continue;
+    }
+
+    for (const MachineBasicBlock *TargetBlock : Description->Targets) {
+      if (TargetBlock == nullptr)
+        return makeUnexpected(ErrorCode::AssemblyLoweringFailed, "jump table has a null target");
+      const mc::MCSymbolRef TargetSymbol = Context->blockSymbol(*TargetBlock);
+      if (!TargetSymbol)
+        return makeUnexpected(ErrorCode::InternalError, "jump-table target has no MC symbol");
+
+      Expected<mc::MCExprRef> Expression = symbolExpression(TargetSymbol);
+      if (Description->Encoding == JumpTableEntryEncoding::LabelDifference32 ||
+          Description->Encoding == JumpTableEntryEncoding::LabelDifference64)
+        Expression = symbolDifference(TargetSymbol, TableSymbol, 0);
+      if (!Expression)
+        return std::unexpected(Expression.error());
+      auto Value = Streamer->emitValue(std::move(*Expression), Description->EntrySize);
+      if (!Value)
+        return std::unexpected(Value.error());
+    }
+  }
+  return {};
+}
+
+} // namespace rcc
diff --git a/backend/lib/AsmPrinter/CMakeLists.txt b/backend/lib/AsmPrinter/CMakeLists.txt
new file mode 100644
index 0000000..6979a71
--- /dev/null
+++ b/backend/lib/AsmPrinter/CMakeLists.txt
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set(
+  RCCBackendAsmPrinterSources
+  AsmPrinter.cpp
+  MachineMCContext.cpp
+  TargetMCInstLowering.cpp
+)
+set(
+  RCCBackendAsmPrinterHeaders
+  "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/AsmPrinter.h"
+  "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/MachineMCContext.h"
+  "${RCC_BACKEND_SOURCE_DIR}/include/rcc/CodeGen/TargetMCInstLowering.h"
+)
+
+add_library(RCCBackendAsmPrinter ${RCCBackendAsmPrinterSources})
+add_library(RCCBackend::AsmPrinter ALIAS RCCBackendAsmPrinter)
+
+rcc_backend_configure_target(RCCBackendAsmPrinter)
+
+target_include_directories(
+  RCCBackendAsmPrinter
+  PUBLIC
+    "$<BUILD_INTERFACE:${RCC_BACKEND_SOURCE_DIR}/include>"
+    "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>"
+)
+target_link_libraries(
+  RCCBackendAsmPrinter
+  PUBLIC
+    RCCBackend::CodeGen
+    RCCBackend::MC
+)
+
+set_target_properties(
+  RCCBackendAsmPrinter
+  PROPERTIES
+    EXPORT_NAME AsmPrinter
+    OUTPUT_NAME RCCBackendAsmPrinter
+)
+
+install(
+  TARGETS RCCBackendAsmPrinter
+  EXPORT RCCBackendTargets
+  ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+  LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+  RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
+)
+
+set(RCCBackendAsmPrinterSourcePaths)
+foreach(Source IN LISTS RCCBackendAsmPrinterSources)
+  list(APPEND RCCBackendAsmPrinterSourcePaths "${CMAKE_CURRENT_SOURCE_DIR}/${Source}")
+endforeach()
+
+rcc_backend_register_format_files(
+  ${RCCBackendAsmPrinterSourcePaths}
+  ${RCCBackendAsmPrinterHeaders}
+)
+rcc_backend_register_tidy_files(${RCCBackendAsmPrinterSourcePaths})
diff --git a/backend/lib/AsmPrinter/MachineMCContext.cpp b/backend/lib/AsmPrinter/MachineMCContext.cpp
new file mode 100644
index 0000000..163e228
--- /dev/null
+++ b/backend/lib/AsmPrinter/MachineMCContext.cpp
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/MachineMCContext.h"
+
+#include "rcc/CodeGen/CompilationUnit.h"
+#include "rcc/CodeGen/GlobalObject.h"
+#include "rcc/CodeGen/MachineBasicBlock.h"
+#include "rcc/CodeGen/MachineConstantPool.h"
+#include "rcc/CodeGen/MachineFunction.h"
+#include "rcc/CodeGen/MachineJumpTableInfo.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <utility>
+
+namespace rcc {
+
+std::size_t MachineMCContext::FunctionIndexHash::operator()(FunctionIndexKey Key) const noexcept {
+  const std::size_t FunctionHash = std::hash<const MachineFunction *>{}(Key.Function);
+  const std::size_t IndexHash = std::hash<std::uint32_t>{}(Key.Index);
+  return FunctionHash ^ (IndexHash + 0x9e3779b9U + (FunctionHash << 6U) + (FunctionHash >> 2U));
+}
+
+Expected<void> MachineMCContext::initialize(const CompilationUnit &Unit) {
+  auto Verification = Unit.verify();
+  if (!Verification)
+    return std::unexpected(Verification.error());
+  for (std::size_t Index = 0; Index < Unit.globalObjectCount(); ++Index) {
+    const GlobalObjectDesc *Object = Unit.globalObjectAt(Index);
+    if (Object == nullptr)
+      return makeUnexpected(ErrorCode::InternalError, "compilation unit contains a null global");
+    auto Symbol = Context->getOrCreateSymbol(Object->Symbol, mc::MCSymbolKind::Object);
+    if (!Symbol)
+      return std::unexpected(Symbol.error());
+    GlobalSymbols.emplace(Object, std::move(*Symbol));
+  }
+  for (std::size_t Index = 0; Index < Unit.functionCount(); ++Index) {
+    const MachineFunction *Function = Unit.functionAt(Index);
+    if (Function == nullptr)
+      return makeUnexpected(ErrorCode::InternalError, "compilation unit contains a null function");
+    auto Initialized = initializeFunction(*Function);
+    if (!Initialized)
+      return std::unexpected(Initialized.error());
+  }
+  return {};
+}
+
+Expected<void> MachineMCContext::initializeFunction(const MachineFunction &Function) {
+  if (FunctionSymbols.contains(&Function))
+    return {};
+
+  auto FunctionSymbol =
+      Context->getOrCreateSymbol(std::string(Function.name()), mc::MCSymbolKind::Function);
+  if (!FunctionSymbol)
+    return std::unexpected(FunctionSymbol.error());
+  FunctionSymbols.emplace(&Function, *FunctionSymbol);
+
+  for (const MachineBasicBlock *Block = Function.firstBlock(); Block != nullptr;
+       Block = Block->next()) {
+    const std::optional<std::size_t> DenseNumber = Block->denseNumber();
+    if (!Block->isLinked() || !DenseNumber) {
+      return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                            "MC symbol initialization requires linked and numbered blocks");
+    }
+    const std::string Name =
+        ".LBB" + std::to_string(Function.stableID().value()) + "_" + std::to_string(*DenseNumber);
+    auto Symbol = Context->getOrCreateSymbol(Name, mc::MCSymbolKind::BasicBlock);
+    if (!Symbol)
+      return std::unexpected(Symbol.error());
+    BlockSymbols.emplace(Block, *Symbol);
+  }
+
+  for (const MachineConstantPoolEntry &Entry : Function.constantPool().entries()) {
+    if (Entry.isTombstone())
+      continue;
+    const std::string Name = ".LCPI" + std::to_string(Function.stableID().value()) + "_" +
+                             std::to_string(Entry.index().value());
+    auto Symbol = Context->getOrCreateSymbol(Name, mc::MCSymbolKind::ConstantPool);
+    if (!Symbol)
+      return std::unexpected(Symbol.error());
+    ConstantPoolSymbols.emplace(
+        FunctionIndexKey{.Function = &Function, .Index = Entry.index().value()}, *Symbol);
+  }
+
+  for (const MachineJumpTableEntry &Entry : Function.jumpTableInfo().tables()) {
+    if (Entry.isTombstone() || Entry.isPending())
+      continue;
+    const std::string Name = ".LJTI" + std::to_string(Function.stableID().value()) + "_" +
+                             std::to_string(Entry.index().value());
+    auto Symbol = Context->getOrCreateSymbol(Name, mc::MCSymbolKind::JumpTable);
+    if (!Symbol)
+      return std::unexpected(Symbol.error());
+    JumpTableSymbols.emplace(
+        FunctionIndexKey{.Function = &Function, .Index = Entry.index().value()}, *Symbol);
+  }
+  return {};
+}
+
+mc::MCSymbolRef MachineMCContext::functionSymbol(const MachineFunction &Function) const noexcept {
+  const auto Position = FunctionSymbols.find(&Function);
+  return Position == FunctionSymbols.end() ? mc::MCSymbolRef{} : Position->second;
+}
+
+mc::MCSymbolRef MachineMCContext::globalSymbol(const GlobalObjectDesc &Object) const noexcept {
+  const auto Position = GlobalSymbols.find(&Object);
+  return Position == GlobalSymbols.end() ? mc::MCSymbolRef{} : Position->second;
+}
+
+mc::MCSymbolRef MachineMCContext::blockSymbol(const MachineBasicBlock &Block) const noexcept {
+  const auto Position = BlockSymbols.find(&Block);
+  return Position == BlockSymbols.end() ? mc::MCSymbolRef{} : Position->second;
+}
+
+mc::MCSymbolRef MachineMCContext::constantPoolSymbol(const MachineFunction &Function,
+                                                     ConstantPoolIndex Index) const noexcept {
+  const auto Position =
+      ConstantPoolSymbols.find(FunctionIndexKey{.Function = &Function, .Index = Index.value()});
+  return Position == ConstantPoolSymbols.end() ? mc::MCSymbolRef{} : Position->second;
+}
+
+mc::MCSymbolRef MachineMCContext::jumpTableSymbol(const MachineFunction &Function,
+                                                  JumpTableIndex Index) const noexcept {
+  const auto Position =
+      JumpTableSymbols.find(FunctionIndexKey{.Function = &Function, .Index = Index.value()});
+  return Position == JumpTableSymbols.end() ? mc::MCSymbolRef{} : Position->second;
+}
+
+Expected<mc::MCSymbolRef> MachineMCContext::symbol(std::string Name, mc::MCSymbolKind Kind) {
+  return Context->getOrCreateSymbol(std::move(Name), Kind);
+}
+
+Expected<mc::MCSymbolRef> MachineMCContext::blockAddressSymbol(std::string_view FunctionName,
+                                                               std::string_view BlockName) const {
+  for (const auto &[Block, Symbol] : BlockSymbols) {
+    if (Block == nullptr || Block->function().name() != FunctionName)
+      continue;
+    const auto IRName = Block->attributes().irBlockName();
+    const auto MachineName = Block->attributes().name();
+    const bool NumericMatch =
+        Block->denseNumber() && std::to_string(*Block->denseNumber()) == BlockName;
+    if ((IRName && *IRName == BlockName) || (MachineName && *MachineName == BlockName) ||
+        NumericMatch)
+      return Symbol;
+  }
+  return makeUnexpected(ErrorCode::AssemblyLoweringFailed,
+                        "block-address operand does not resolve to an emitted block symbol");
+}
+
+} // namespace rcc
diff --git a/backend/lib/AsmPrinter/TargetMCInstLowering.cpp b/backend/lib/AsmPrinter/TargetMCInstLowering.cpp
new file mode 100644
index 0000000..c171034
--- /dev/null
+++ b/backend/lib/AsmPrinter/TargetMCInstLowering.cpp
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/TargetMCInstLowering.h"
+
+namespace rcc {
+
+Expected<void> TargetMCInstLowering::emitTerminalInstruction(const MachineInstr &,
+                                                             MachineMCContext &,
+                                                             mc::MCStreamer &) const {
+  return makeUnexpected(ErrorCode::Unsupported,
+                        "target does not support this terminal emission instruction");
+}
+
+Expected<void> TargetMCInstLowering::emitFileHeader(MachineMCContext &, mc::MCStreamer &) const {
+  return {};
+}
+
+Expected<void> TargetMCInstLowering::emitFileTrailer(MachineMCContext &, mc::MCStreamer &) const {
+  return {};
+}
+
+Expected<void> TargetMCInstLowering::emitGenericConstant(const GenericConstantData &, std::uint64_t,
+                                                         MachineMCContext &,
+                                                         mc::MCStreamer &) const {
+  return makeUnexpected(ErrorCode::Unsupported,
+                        "target does not support assembly emission for generic constants");
+}
+
+Expected<void> TargetMCInstLowering::emitGlobalInitializer(const GlobalInitializer &,
+                                                           MachineMCContext &,
+                                                           mc::MCStreamer &) const {
+  return makeUnexpected(ErrorCode::Unsupported,
+                        "target does not support assembly emission for global initializers");
+}
+
+Expected<void> TargetMCInstLowering::emitTargetConstant(const TargetConstant &, MachineMCContext &,
+                                                        mc::MCStreamer &) const {
+  return makeUnexpected(ErrorCode::Unsupported,
+                        "target does not support assembly emission for this target constant");
+}
+
+Expected<void> TargetMCInstLowering::emitTargetJumpTable(const MachineFunction &,
+                                                         const MachineJumpTableEntry &,
+                                                         MachineMCContext &,
+                                                         mc::MCStreamer &) const {
+  return makeUnexpected(ErrorCode::Unsupported, "target does not support this jump-table encoding");
+}
+
+} // namespace rcc