[RISCV] Add generated RV64GC register description

Add an RCC-owned build-time target description generator and the initial RV64GC register model. Keep ABI aliases separate from canonical MIR register spelling.

2 files changed, 1184 insertions, 0 deletions

diff --git a/backend/lib/Target/Description/TargetDescriptionGenerator.cpp b/backend/lib/Target/Description/TargetDescriptionGenerator.cpp
new file mode 100644
index 0000000..259c9fe
--- /dev/null
+++ b/backend/lib/Target/Description/TargetDescriptionGenerator.cpp
@@ -0,0 +1,1150 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "TargetDescriptionGenerator.h"
+
+#include "rcc/Support/YAML.h"
+
+#include <algorithm>
+#include <array>
+#include <cctype>
+#include <charconv>
+#include <cstdint>
+#include <limits>
+#include <optional>
+#include <ranges>
+#include <span>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+namespace rcc::targetgen {
+namespace {
+
+struct SourceTarget final {
+  std::string Namespace;
+  std::string Name;
+  std::string Triple;
+  std::string CPU;
+  std::string ABI;
+  std::string DataLayout;
+  std::vector<std::string> Features;
+  TextRange Range;
+};
+
+struct SourceRegisterUnit final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  TextRange Range;
+};
+
+struct SourceRegisterUnitLane final {
+  std::string UnitSymbol;
+  std::uint64_t Lanes = 0;
+  TextRange Range;
+};
+
+struct SourceRegister final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::uint32_t Encoding = 0;
+  std::uint32_t DwarfRegister = 0;
+  std::vector<SourceRegisterUnitLane> Units;
+  bool IsConstant = false;
+  bool IsArtificial = false;
+  bool IsReserved = false;
+  std::vector<std::string> AlternativeNames;
+  TextRange Range;
+};
+
+struct SourceRegisterBank final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::uint32_t MaximumSizeInBits = 0;
+  TextRange Range;
+};
+
+struct SourceRegisterClass final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::string BankSymbol;
+  std::uint32_t SizeInBits = 0;
+  std::uint32_t SpillSizeInBits = 0;
+  std::uint32_t SpillAlignmentInBits = 0;
+  std::uint64_t Lanes = 0;
+  std::vector<std::string> RegisterSymbols;
+  std::vector<std::string> AllocationOrderSymbols;
+  bool Allocatable = true;
+  std::uint32_t CopyCost = 1;
+  TextRange Range;
+};
+
+struct SourceRegisterMask final {
+  std::string Name;
+  std::vector<std::string> PreservedRegisterSymbols;
+  TextRange Range;
+};
+
+struct DescriptionAST final {
+  SourceTarget Target;
+  std::vector<SourceRegisterUnit> RegisterUnits;
+  std::vector<SourceRegister> Registers;
+  std::vector<SourceRegisterBank> RegisterBanks;
+  std::vector<SourceRegisterClass> RegisterClasses;
+  std::vector<SourceRegisterMask> RegisterMasks;
+};
+
+struct NormalizedRegisterUnitLane final {
+  std::uint32_t UnitID = 0;
+  std::uint64_t Lanes = 0;
+};
+
+struct NormalizedRegister final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::uint32_t Encoding = 0;
+  std::uint32_t DwarfRegister = 0;
+  std::vector<NormalizedRegisterUnitLane> Units;
+  bool IsConstant = false;
+  bool IsArtificial = false;
+  bool IsReserved = false;
+  std::vector<std::string> AlternativeNames;
+};
+
+struct NormalizedRegisterBank final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::uint32_t MaximumSizeInBits = 0;
+  std::vector<std::uint32_t> RegisterClasses;
+};
+
+struct NormalizedRegisterClass final {
+  std::uint32_t ID = 0;
+  std::string Symbol;
+  std::string Name;
+  std::uint32_t BankID = 0;
+  std::uint32_t SizeInBits = 0;
+  std::uint32_t SpillSizeInBits = 0;
+  std::uint32_t SpillAlignmentInBits = 0;
+  std::uint64_t Lanes = 0;
+  std::vector<std::uint32_t> Registers;
+  std::vector<std::uint32_t> AllocationOrder;
+  bool Allocatable = true;
+  std::uint32_t CopyCost = 1;
+};
+
+struct NormalizedRegisterMask final {
+  std::string Name;
+  std::vector<std::uint32_t> PreservedRegisters;
+};
+
+struct NormalizedTargetModel final {
+  SourceTarget Target;
+  std::vector<SourceRegisterUnit> RegisterUnits;
+  std::vector<NormalizedRegister> Registers;
+  std::vector<NormalizedRegisterBank> RegisterBanks;
+  std::vector<NormalizedRegisterClass> RegisterClasses;
+  std::vector<NormalizedRegisterMask> RegisterMasks;
+};
+
+[[nodiscard]] std::string lowerASCII(std::string_view Value) {
+  std::string Result(Value);
+  for (char &Character : Result) {
+    if (Character >= 'A' && Character <= 'Z')
+      Character = static_cast<char>(Character - 'A' + 'a');
+  }
+  return Result;
+}
+
+[[nodiscard]] bool isIdentifier(std::string_view Value) noexcept {
+  if (Value.empty())
+    return false;
+  const auto IsHead = [](unsigned char Character) {
+    return std::isalpha(Character) != 0 || Character == '_';
+  };
+  const auto IsTail = [](unsigned char Character) {
+    return std::isalnum(Character) != 0 || Character == '_';
+  };
+  if (!IsHead(static_cast<unsigned char>(Value.front())))
+    return false;
+  return std::ranges::all_of(Value.substr(1), [IsTail](char Character) {
+    return IsTail(static_cast<unsigned char>(Character));
+  });
+}
+
+[[nodiscard]] std::string upperIdentifier(std::string_view Value) {
+  std::string Result;
+  Result.reserve(Value.size());
+  for (const char Character : Value) {
+    if (Character >= 'a' && Character <= 'z')
+      Result.push_back(static_cast<char>(Character - 'a' + 'A'));
+    else if ((Character >= 'A' && Character <= 'Z') || (Character >= '0' && Character <= '9'))
+      Result.push_back(Character);
+    else
+      Result.push_back('_');
+  }
+  return Result;
+}
+
+void appendQuoted(std::ostream &Output, std::string_view Value) {
+  Output << '"';
+  for (const char Character : Value) {
+    switch (Character) {
+    case '\\':
+      Output << "\\\\";
+      break;
+    case '"':
+      Output << "\\\"";
+      break;
+    case '\n':
+      Output << "\\n";
+      break;
+    case '\r':
+      Output << "\\r";
+      break;
+    case '\t':
+      Output << "\\t";
+      break;
+    default:
+      Output << Character;
+      break;
+    }
+  }
+  Output << '"';
+}
+
+class ASTParser final {
+public:
+  explicit ASTParser(const yaml::Stream &Input) : Input(Input) {}
+
+  [[nodiscard]] std::optional<DescriptionAST> parse() {
+    const std::span<const yaml::Document> Documents = Input.documents();
+    if (Documents.size() != 1) {
+      fail(Input.source().range(0, Input.source().text().size()),
+           "target description must contain exactly one YAML document");
+      return std::nullopt;
+    }
+
+    const yaml::Node *Root = Input.node(Documents.front().Root);
+    if (!requireMapping(Root, "target description root"))
+      return std::nullopt;
+    if (!checkKeys(*Root,
+                   {"schema", "target", "register_units", "registers", "register_banks",
+                    "register_classes", "register_masks"},
+                   "target description root")) {
+      return std::nullopt;
+    }
+
+    const yaml::Node *SchemaNode = requiredNode(*Root, "schema", "target description root");
+    if (SchemaNode == nullptr)
+      return std::nullopt;
+    const auto Schema = scalar(*SchemaNode, "target description schema");
+    if (!Schema || *Schema != "rcc-target-description-v1") {
+      if (Schema)
+        fail(SchemaNode->range(), "unsupported target description schema");
+      return std::nullopt;
+    }
+
+    DescriptionAST Result;
+    const yaml::Node *TargetNode = requiredNode(*Root, "target", "target description root");
+    if (TargetNode == nullptr || !parseTarget(*TargetNode, Result.Target))
+      return std::nullopt;
+    const yaml::Node *UnitsNode = requiredNode(*Root, "register_units", "target description root");
+    const yaml::Node *RegistersNode = requiredNode(*Root, "registers", "target description root");
+    const yaml::Node *BanksNode = requiredNode(*Root, "register_banks", "target description root");
+    const yaml::Node *ClassesNode =
+        requiredNode(*Root, "register_classes", "target description root");
+    const yaml::Node *MasksNode = requiredNode(*Root, "register_masks", "target description root");
+    if (UnitsNode == nullptr || RegistersNode == nullptr || BanksNode == nullptr ||
+        ClassesNode == nullptr || MasksNode == nullptr ||
+        !parseRegisterUnits(*UnitsNode, Result.RegisterUnits) ||
+        !parseRegisters(*RegistersNode, Result.Registers) ||
+        !parseRegisterBanks(*BanksNode, Result.RegisterBanks) ||
+        !parseRegisterClasses(*ClassesNode, Result.RegisterClasses) ||
+        !parseRegisterMasks(*MasksNode, Result.RegisterMasks)) {
+      return std::nullopt;
+    }
+    return Result;
+  }
+
+  [[nodiscard]] std::vector<TextDiagnostic> takeDiagnostics() {
+    return std::move(Diagnostics);
+  }
+
+private:
+  void fail(TextRange Range, std::string Message) {
+    Diagnostics.push_back({
+        .Severity = DiagnosticSeverity::Error,
+        .Category = "target-description",
+        .Message = std::move(Message),
+        .SourceName = std::string(Input.source().name()),
+        .Range = Range,
+    });
+  }
+
+  [[nodiscard]] bool requireMapping(const yaml::Node *Node, std::string_view Context) {
+    if (Node != nullptr && Node->kind() == yaml::NodeKind::Mapping)
+      return true;
+    fail(Node == nullptr ? Input.source().range(0, 0) : Node->range(),
+         std::string(Context) + " must be a mapping");
+    return false;
+  }
+
+  [[nodiscard]] bool requireSequence(const yaml::Node *Node, std::string_view Context) {
+    if (Node != nullptr && Node->kind() == yaml::NodeKind::Sequence)
+      return true;
+    fail(Node == nullptr ? Input.source().range(0, 0) : Node->range(),
+         std::string(Context) + " must be a sequence");
+    return false;
+  }
+
+  [[nodiscard]] bool checkKeys(const yaml::Node &Mapping,
+                               std::initializer_list<std::string_view> Allowed,
+                               std::string_view Context) {
+    for (const yaml::MappingEntry &Entry : Mapping.mapping()) {
+      const bool IsAllowed =
+          std::ranges::any_of(Allowed, [&Entry](std::string_view Key) { return Entry.Key == Key; });
+      if (!IsAllowed) {
+        fail(Entry.KeyRange, std::string(Context) + " has unknown key '" + Entry.Key + "'");
+        return false;
+      }
+    }
+    return true;
+  }
+
+  [[nodiscard]] const yaml::Node *requiredNode(const yaml::Node &Mapping, std::string_view Key,
+                                               std::string_view Context) {
+    const std::optional<yaml::NodeID> Value = Mapping.mappingValue(Key);
+    if (Value) {
+      const yaml::Node *Node = Input.node(*Value);
+      if (Node != nullptr)
+        return Node;
+    }
+    fail(Mapping.range(),
+         std::string(Context) + " is missing required key '" + std::string(Key) + "'");
+    return nullptr;
+  }
+
+  [[nodiscard]] std::optional<std::string>
+  requiredScalar(const yaml::Node &Mapping, std::string_view Key, std::string_view Context) {
+    const yaml::Node *Node = requiredNode(Mapping, Key, Context);
+    if (Node == nullptr)
+      return std::nullopt;
+    return scalar(*Node, std::string(Context) + " key '" + std::string(Key) + "'");
+  }
+
+  [[nodiscard]] std::optional<std::string> scalar(const yaml::Node &Node,
+                                                  std::string_view Context) {
+    if (Node.kind() != yaml::NodeKind::Scalar) {
+      fail(Node.range(), std::string(Context) + " must be a scalar");
+      return std::nullopt;
+    }
+    return std::string(Node.scalar());
+  }
+
+  [[nodiscard]] std::optional<std::uint64_t> unsignedInteger(const yaml::Node &Node,
+                                                             std::string_view Context) {
+    const auto Text = scalar(Node, Context);
+    if (!Text)
+      return std::nullopt;
+    std::uint64_t Result = 0;
+    const auto [End, Error] =
+        std::from_chars(Text->data(), Text->data() + Text->size(), Result, 10);
+    if (Error != std::errc{} || End != Text->data() + Text->size()) {
+      fail(Node.range(), std::string(Context) + " must be an unsigned decimal integer");
+      return std::nullopt;
+    }
+    return Result;
+  }
+
+  [[nodiscard]] std::optional<std::uint32_t> unsignedInteger32(const yaml::Node &Node,
+                                                               std::string_view Context) {
+    const auto Value = unsignedInteger(Node, Context);
+    if (!Value)
+      return std::nullopt;
+    if (*Value > std::numeric_limits<std::uint32_t>::max()) {
+      fail(Node.range(), std::string(Context) + " is outside the uint32 range");
+      return std::nullopt;
+    }
+    return static_cast<std::uint32_t>(*Value);
+  }
+
+  [[nodiscard]] std::optional<bool> boolean(const yaml::Node &Node, std::string_view Context) {
+    const auto Text = scalar(Node, Context);
+    if (!Text)
+      return std::nullopt;
+    if (*Text == "true")
+      return true;
+    if (*Text == "false")
+      return false;
+    fail(Node.range(), std::string(Context) + " must be 'true' or 'false'");
+    return std::nullopt;
+  }
+
+  [[nodiscard]] std::optional<std::vector<std::string>> scalarSequence(const yaml::Node &Node,
+                                                                       std::string_view Context) {
+    if (!requireSequence(&Node, Context))
+      return std::nullopt;
+    std::vector<std::string> Result;
+    for (const yaml::NodeID Value : Node.sequence()) {
+      const yaml::Node *Element = Input.node(Value);
+      if (Element == nullptr)
+        return std::nullopt;
+      const auto Text = scalar(*Element, Context);
+      if (!Text)
+        return std::nullopt;
+      Result.push_back(*Text);
+    }
+    return Result;
+  }
+
+  [[nodiscard]] bool parseTarget(const yaml::Node &Node, SourceTarget &Result) {
+    if (!requireMapping(&Node, "target"))
+      return false;
+    if (!checkKeys(Node, {"namespace", "name", "triple", "cpu", "abi", "data_layout", "features"},
+                   "target")) {
+      return false;
+    }
+    const auto Namespace = requiredScalar(Node, "namespace", "target");
+    const auto Name = requiredScalar(Node, "name", "target");
+    const auto Triple = requiredScalar(Node, "triple", "target");
+    const auto CPU = requiredScalar(Node, "cpu", "target");
+    const auto ABI = requiredScalar(Node, "abi", "target");
+    const auto DataLayout = requiredScalar(Node, "data_layout", "target");
+    const yaml::Node *Features = requiredNode(Node, "features", "target");
+    if (!Namespace || !Name || !Triple || !CPU || !ABI || !DataLayout || Features == nullptr)
+      return false;
+    const auto ParsedFeatures = scalarSequence(*Features, "target features");
+    if (!ParsedFeatures)
+      return false;
+    Result = {
+        .Namespace = *Namespace,
+        .Name = *Name,
+        .Triple = *Triple,
+        .CPU = *CPU,
+        .ABI = *ABI,
+        .DataLayout = *DataLayout,
+        .Features = *ParsedFeatures,
+        .Range = Node.range(),
+    };
+    return true;
+  }
+
+  [[nodiscard]] bool parseRegisterUnits(const yaml::Node &Node,
+                                        std::vector<SourceRegisterUnit> &Result) {
+    if (!requireSequence(&Node, "register_units"))
+      return false;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register unit"))
+        return false;
+      if (!checkKeys(*Element, {"id", "symbol", "name"}, "register unit"))
+        return false;
+      const yaml::Node *IDNode = requiredNode(*Element, "id", "register unit");
+      const auto Symbol = requiredScalar(*Element, "symbol", "register unit");
+      const auto Name = requiredScalar(*Element, "name", "register unit");
+      if (IDNode == nullptr || !Symbol || !Name)
+        return false;
+      const auto ID = unsignedInteger32(*IDNode, "register unit id");
+      if (!ID)
+        return false;
+      Result.push_back({.ID = *ID, .Symbol = *Symbol, .Name = *Name, .Range = Element->range()});
+    }
+    return true;
+  }
+
+  [[nodiscard]] std::optional<std::vector<SourceRegisterUnitLane>>
+  parseRegisterUnitLanes(const yaml::Node &Node) {
+    if (!requireSequence(&Node, "register units"))
+      return std::nullopt;
+    std::vector<SourceRegisterUnitLane> Result;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register unit lane"))
+        return std::nullopt;
+      if (!checkKeys(*Element, {"unit", "lanes"}, "register unit lane"))
+        return std::nullopt;
+      const auto Unit = requiredScalar(*Element, "unit", "register unit lane");
+      const yaml::Node *LanesNode = requiredNode(*Element, "lanes", "register unit lane");
+      if (!Unit || LanesNode == nullptr)
+        return std::nullopt;
+      const auto Lanes = unsignedInteger(*LanesNode, "register unit lane lanes");
+      if (!Lanes)
+        return std::nullopt;
+      Result.push_back({.UnitSymbol = *Unit, .Lanes = *Lanes, .Range = Element->range()});
+    }
+    return Result;
+  }
+
+  [[nodiscard]] bool parseRegisters(const yaml::Node &Node, std::vector<SourceRegister> &Result) {
+    if (!requireSequence(&Node, "registers"))
+      return false;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register"))
+        return false;
+      if (!checkKeys(*Element,
+                     {"id", "symbol", "name", "encoding", "dwarf_register", "units", "constant",
+                      "artificial", "reserved", "aliases"},
+                     "register")) {
+        return false;
+      }
+      const yaml::Node *IDNode = requiredNode(*Element, "id", "register");
+      const auto Symbol = requiredScalar(*Element, "symbol", "register");
+      const auto Name = requiredScalar(*Element, "name", "register");
+      const yaml::Node *EncodingNode = requiredNode(*Element, "encoding", "register");
+      const yaml::Node *DwarfNode = requiredNode(*Element, "dwarf_register", "register");
+      const yaml::Node *UnitsNode = requiredNode(*Element, "units", "register");
+      if (IDNode == nullptr || !Symbol || !Name || EncodingNode == nullptr ||
+          DwarfNode == nullptr || UnitsNode == nullptr) {
+        return false;
+      }
+      const auto ID = unsignedInteger32(*IDNode, "register id");
+      const auto Encoding = unsignedInteger32(*EncodingNode, "register encoding");
+      const auto DwarfRegister = unsignedInteger32(*DwarfNode, "register DWARF number");
+      const auto Units = parseRegisterUnitLanes(*UnitsNode);
+      if (!ID || !Encoding || !DwarfRegister || !Units)
+        return false;
+
+      SourceRegister Register{
+          .ID = *ID,
+          .Symbol = *Symbol,
+          .Name = *Name,
+          .Encoding = *Encoding,
+          .DwarfRegister = *DwarfRegister,
+          .Units = *Units,
+          .IsConstant = false,
+          .IsArtificial = false,
+          .IsReserved = false,
+          .AlternativeNames = {},
+          .Range = Element->range(),
+      };
+      if (const yaml::Node *Constant = optionalNode(*Element, "constant")) {
+        const auto Value = boolean(*Constant, "register constant");
+        if (!Value)
+          return false;
+        Register.IsConstant = *Value;
+      }
+      if (const yaml::Node *Artificial = optionalNode(*Element, "artificial")) {
+        const auto Value = boolean(*Artificial, "register artificial");
+        if (!Value)
+          return false;
+        Register.IsArtificial = *Value;
+      }
+      if (const yaml::Node *Reserved = optionalNode(*Element, "reserved")) {
+        const auto Value = boolean(*Reserved, "register reserved");
+        if (!Value)
+          return false;
+        Register.IsReserved = *Value;
+      }
+      if (const yaml::Node *Aliases = optionalNode(*Element, "aliases")) {
+        const auto Values = scalarSequence(*Aliases, "register aliases");
+        if (!Values)
+          return false;
+        Register.AlternativeNames = *Values;
+      }
+      Result.push_back(std::move(Register));
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool parseRegisterBanks(const yaml::Node &Node,
+                                        std::vector<SourceRegisterBank> &Result) {
+    if (!requireSequence(&Node, "register_banks"))
+      return false;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register bank"))
+        return false;
+      if (!checkKeys(*Element, {"id", "symbol", "name", "maximum_size_bits"}, "register bank"))
+        return false;
+      const yaml::Node *IDNode = requiredNode(*Element, "id", "register bank");
+      const auto Symbol = requiredScalar(*Element, "symbol", "register bank");
+      const auto Name = requiredScalar(*Element, "name", "register bank");
+      const yaml::Node *SizeNode = requiredNode(*Element, "maximum_size_bits", "register bank");
+      if (IDNode == nullptr || !Symbol || !Name || SizeNode == nullptr)
+        return false;
+      const auto ID = unsignedInteger32(*IDNode, "register bank id");
+      const auto Size = unsignedInteger32(*SizeNode, "register bank maximum_size_bits");
+      if (!ID || !Size)
+        return false;
+      Result.push_back({.ID = *ID,
+                        .Symbol = *Symbol,
+                        .Name = *Name,
+                        .MaximumSizeInBits = *Size,
+                        .Range = Element->range()});
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool parseRegisterClasses(const yaml::Node &Node,
+                                          std::vector<SourceRegisterClass> &Result) {
+    if (!requireSequence(&Node, "register_classes"))
+      return false;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register class"))
+        return false;
+      if (!checkKeys(*Element,
+                     {"id", "symbol", "name", "bank", "size_bits", "spill_size_bits",
+                      "spill_alignment_bits", "lanes", "registers", "allocation_order",
+                      "allocatable", "copy_cost"},
+                     "register class")) {
+        return false;
+      }
+      const yaml::Node *IDNode = requiredNode(*Element, "id", "register class");
+      const auto Symbol = requiredScalar(*Element, "symbol", "register class");
+      const auto Name = requiredScalar(*Element, "name", "register class");
+      const auto Bank = requiredScalar(*Element, "bank", "register class");
+      const yaml::Node *SizeNode = requiredNode(*Element, "size_bits", "register class");
+      const yaml::Node *SpillSizeNode = requiredNode(*Element, "spill_size_bits", "register class");
+      const yaml::Node *SpillAlignmentNode =
+          requiredNode(*Element, "spill_alignment_bits", "register class");
+      const yaml::Node *LanesNode = requiredNode(*Element, "lanes", "register class");
+      const yaml::Node *RegistersNode = requiredNode(*Element, "registers", "register class");
+      const yaml::Node *AllocationNode =
+          requiredNode(*Element, "allocation_order", "register class");
+      if (IDNode == nullptr || !Symbol || !Name || !Bank || SizeNode == nullptr ||
+          SpillSizeNode == nullptr || SpillAlignmentNode == nullptr || LanesNode == nullptr ||
+          RegistersNode == nullptr || AllocationNode == nullptr) {
+        return false;
+      }
+      const auto ID = unsignedInteger32(*IDNode, "register class id");
+      const auto Size = unsignedInteger32(*SizeNode, "register class size_bits");
+      const auto SpillSize = unsignedInteger32(*SpillSizeNode, "register class spill_size_bits");
+      const auto SpillAlignment =
+          unsignedInteger32(*SpillAlignmentNode, "register class spill_alignment_bits");
+      const auto Lanes = unsignedInteger(*LanesNode, "register class lanes");
+      const auto Registers = scalarSequence(*RegistersNode, "register class registers");
+      const auto AllocationOrder =
+          scalarSequence(*AllocationNode, "register class allocation_order");
+      if (!ID || !Size || !SpillSize || !SpillAlignment || !Lanes || !Registers ||
+          !AllocationOrder) {
+        return false;
+      }
+      SourceRegisterClass RegisterClass{
+          .ID = *ID,
+          .Symbol = *Symbol,
+          .Name = *Name,
+          .BankSymbol = *Bank,
+          .SizeInBits = *Size,
+          .SpillSizeInBits = *SpillSize,
+          .SpillAlignmentInBits = *SpillAlignment,
+          .Lanes = *Lanes,
+          .RegisterSymbols = *Registers,
+          .AllocationOrderSymbols = *AllocationOrder,
+          .Range = Element->range(),
+      };
+      if (const yaml::Node *Allocatable = optionalNode(*Element, "allocatable")) {
+        const auto Value = boolean(*Allocatable, "register class allocatable");
+        if (!Value)
+          return false;
+        RegisterClass.Allocatable = *Value;
+      }
+      if (const yaml::Node *CopyCost = optionalNode(*Element, "copy_cost")) {
+        const auto Value = unsignedInteger32(*CopyCost, "register class copy_cost");
+        if (!Value)
+          return false;
+        RegisterClass.CopyCost = *Value;
+      }
+      Result.push_back(std::move(RegisterClass));
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool parseRegisterMasks(const yaml::Node &Node,
+                                        std::vector<SourceRegisterMask> &Result) {
+    if (!requireSequence(&Node, "register_masks"))
+      return false;
+    for (const yaml::NodeID ElementID : Node.sequence()) {
+      const yaml::Node *Element = Input.node(ElementID);
+      if (!requireMapping(Element, "register mask"))
+        return false;
+      if (!checkKeys(*Element, {"name", "preserved"}, "register mask"))
+        return false;
+      const auto Name = requiredScalar(*Element, "name", "register mask");
+      const yaml::Node *PreservedNode = requiredNode(*Element, "preserved", "register mask");
+      if (!Name || PreservedNode == nullptr)
+        return false;
+      const auto Preserved = scalarSequence(*PreservedNode, "register mask preserved");
+      if (!Preserved)
+        return false;
+      Result.push_back(
+          {.Name = *Name, .PreservedRegisterSymbols = *Preserved, .Range = Element->range()});
+    }
+    return true;
+  }
+
+  [[nodiscard]] const yaml::Node *optionalNode(const yaml::Node &Mapping,
+                                               std::string_view Key) const noexcept {
+    const std::optional<yaml::NodeID> Value = Mapping.mappingValue(Key);
+    return Value ? Input.node(*Value) : nullptr;
+  }
+
+  const yaml::Stream &Input;
+  std::vector<TextDiagnostic> Diagnostics;
+};
+
+class ModelNormalizer final {
+public:
+  ModelNormalizer(const DescriptionAST &Input, std::string SourceName)
+      : Input(Input), SourceName(std::move(SourceName)) {}
+
+  [[nodiscard]] std::optional<NormalizedTargetModel> normalize() {
+    if (!validateTarget())
+      return std::nullopt;
+
+    NormalizedTargetModel Result;
+    Result.Target = Input.Target;
+    Result.RegisterUnits = Input.RegisterUnits;
+    if (!normalizeRegisterUnits() || !normalizeRegisters(Result) ||
+        !normalizeRegisterBanks(Result) || !normalizeRegisterClasses(Result) ||
+        !normalizeRegisterMasks(Result)) {
+      return std::nullopt;
+    }
+    return Result;
+  }
+
+  [[nodiscard]] std::vector<TextDiagnostic> takeDiagnostics() {
+    return std::move(Diagnostics);
+  }
+
+private:
+  void fail(TextRange Range, std::string Message) {
+    Diagnostics.push_back({
+        .Severity = DiagnosticSeverity::Error,
+        .Category = "target-description",
+        .Message = std::move(Message),
+        .SourceName = SourceName,
+        .Range = Range,
+    });
+  }
+
+  [[nodiscard]] bool validateTarget() {
+    if (!isIdentifier(Input.Target.Namespace)) {
+      fail(Input.Target.Range, "target namespace must be a C++ identifier");
+      return false;
+    }
+    if (Input.Target.Name.empty() || Input.Target.Triple.empty() || Input.Target.CPU.empty() ||
+        Input.Target.ABI.empty() || Input.Target.DataLayout.empty() ||
+        Input.Target.Features.empty()) {
+      fail(Input.Target.Range, "target metadata fields and feature list must be nonempty");
+      return false;
+    }
+    std::unordered_set<std::string> Features;
+    for (const std::string &Feature : Input.Target.Features) {
+      if (Feature.empty() || !Features.insert(Feature).second) {
+        fail(Input.Target.Range, "target feature names must be nonempty and unique");
+        return false;
+      }
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool normalizeRegisterUnits() {
+    if (Input.RegisterUnits.empty()) {
+      fail(Input.Target.Range, "target description requires at least one register unit");
+      return false;
+    }
+    std::unordered_set<std::uint32_t> IDs;
+    std::unordered_set<std::string> Symbols;
+    std::unordered_set<std::string> Names;
+    for (const SourceRegisterUnit &Unit : Input.RegisterUnits) {
+      if (Unit.ID == 0 || !isIdentifier(Unit.Symbol) || Unit.Name.empty() ||
+          !IDs.insert(Unit.ID).second || !Symbols.insert(Unit.Symbol).second ||
+          !Names.insert(lowerASCII(Unit.Name)).second) {
+        fail(Unit.Range,
+             "register units require nonzero unique IDs, unique symbols, and unique names");
+        return false;
+      }
+      UnitBySymbol.emplace(Unit.Symbol, Unit.ID);
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool normalizeRegisters(NormalizedTargetModel &Result) {
+    if (Input.Registers.empty()) {
+      fail(Input.Target.Range, "target description requires at least one physical register");
+      return false;
+    }
+    std::unordered_set<std::uint32_t> IDs;
+    std::unordered_set<std::string> Symbols;
+    std::unordered_set<std::string> Names;
+    std::unordered_set<std::uint32_t> DwarfRegisters;
+    for (const SourceRegister &Register : Input.Registers) {
+      if (Register.ID == 0 || !isIdentifier(Register.Symbol) || Register.Name.empty() ||
+          !IDs.insert(Register.ID).second || !Symbols.insert(Register.Symbol).second ||
+          !Names.insert(lowerASCII(Register.Name)).second ||
+          !DwarfRegisters.insert(Register.DwarfRegister).second || Register.Units.empty()) {
+        fail(Register.Range, "registers require nonzero unique IDs, symbols, canonical names, "
+                             "DWARF numbers, and units");
+        return false;
+      }
+      RegisterBySymbol.emplace(Register.Symbol, Register.ID);
+      NormalizedRegister Normalized{
+          .ID = Register.ID,
+          .Symbol = Register.Symbol,
+          .Name = Register.Name,
+          .Encoding = Register.Encoding,
+          .DwarfRegister = Register.DwarfRegister,
+          .Units = {},
+          .IsConstant = Register.IsConstant,
+          .IsArtificial = Register.IsArtificial,
+          .IsReserved = Register.IsReserved,
+          .AlternativeNames = Register.AlternativeNames,
+      };
+      std::unordered_set<std::uint32_t> Units;
+      for (const SourceRegisterUnitLane &Unit : Register.Units) {
+        const auto Position = UnitBySymbol.find(Unit.UnitSymbol);
+        if (Position == UnitBySymbol.end() || Unit.Lanes == 0 ||
+            !Units.insert(Position->second).second) {
+          fail(Unit.Range,
+               "register units must name distinct declared units with nonzero lane masks");
+          return false;
+        }
+        Normalized.Units.push_back({.UnitID = Position->second, .Lanes = Unit.Lanes});
+      }
+      for (const std::string &Alias : Register.AlternativeNames) {
+        if (Alias.empty() || !Names.insert(lowerASCII(Alias)).second) {
+          fail(Register.Range,
+               "register ABI aliases must be nonempty and unique across all register names");
+          return false;
+        }
+      }
+      Result.Registers.push_back(std::move(Normalized));
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool normalizeRegisterBanks(NormalizedTargetModel &Result) {
+    if (Input.RegisterBanks.empty()) {
+      fail(Input.Target.Range, "target description requires at least one register bank");
+      return false;
+    }
+    std::unordered_set<std::uint32_t> IDs;
+    std::unordered_set<std::string> Symbols;
+    std::unordered_set<std::string> Names;
+    for (const SourceRegisterBank &Bank : Input.RegisterBanks) {
+      if (Bank.ID == 0 || !isIdentifier(Bank.Symbol) || Bank.Name.empty() ||
+          Bank.MaximumSizeInBits == 0 || !IDs.insert(Bank.ID).second ||
+          !Symbols.insert(Bank.Symbol).second || !Names.insert(lowerASCII(Bank.Name)).second) {
+        fail(Bank.Range,
+             "register banks require nonzero unique IDs, symbols, names, and maximum sizes");
+        return false;
+      }
+      BankBySymbol.emplace(Bank.Symbol, Bank.ID);
+      Result.RegisterBanks.push_back({
+          .ID = Bank.ID,
+          .Symbol = Bank.Symbol,
+          .Name = Bank.Name,
+          .MaximumSizeInBits = Bank.MaximumSizeInBits,
+          .RegisterClasses = {},
+      });
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool normalizeRegisterClasses(NormalizedTargetModel &Result) {
+    if (Input.RegisterClasses.empty()) {
+      fail(Input.Target.Range, "target description requires at least one register class");
+      return false;
+    }
+    std::unordered_set<std::uint32_t> IDs;
+    std::unordered_set<std::string> Symbols;
+    std::unordered_set<std::string> Names;
+    for (const SourceRegisterClass &Class : Input.RegisterClasses) {
+      const auto Bank = BankBySymbol.find(Class.BankSymbol);
+      if (Class.ID == 0 || !isIdentifier(Class.Symbol) || Class.Name.empty() ||
+          Bank == BankBySymbol.end() || Class.SizeInBits == 0 || Class.SpillSizeInBits == 0 ||
+          Class.SpillAlignmentInBits == 0 || Class.Lanes == 0 || Class.RegisterSymbols.empty() ||
+          !IDs.insert(Class.ID).second || !Symbols.insert(Class.Symbol).second ||
+          !Names.insert(lowerASCII(Class.Name)).second) {
+        fail(Class.Range, "register classes require unique IDs, symbols, names, a declared bank, "
+                          "sizes, lanes, and members");
+        return false;
+      }
+      ClassBySymbol.emplace(Class.Symbol, Class.ID);
+      NormalizedRegisterClass Normalized{
+          .ID = Class.ID,
+          .Symbol = Class.Symbol,
+          .Name = Class.Name,
+          .BankID = Bank->second,
+          .SizeInBits = Class.SizeInBits,
+          .SpillSizeInBits = Class.SpillSizeInBits,
+          .SpillAlignmentInBits = Class.SpillAlignmentInBits,
+          .Lanes = Class.Lanes,
+          .Registers = {},
+          .AllocationOrder = {},
+          .Allocatable = Class.Allocatable,
+          .CopyCost = Class.CopyCost,
+      };
+      std::unordered_set<std::uint32_t> Members;
+      for (const std::string &Symbol : Class.RegisterSymbols) {
+        const auto Register = RegisterBySymbol.find(Symbol);
+        if (Register == RegisterBySymbol.end() || !Members.insert(Register->second).second) {
+          fail(Class.Range, "register class members must reference distinct declared registers");
+          return false;
+        }
+        Normalized.Registers.push_back(Register->second);
+      }
+      std::unordered_set<std::uint32_t> Allocation;
+      for (const std::string &Symbol : Class.AllocationOrderSymbols) {
+        const auto Register = RegisterBySymbol.find(Symbol);
+        if (Register == RegisterBySymbol.end() || !Members.contains(Register->second) ||
+            !Allocation.insert(Register->second).second) {
+          fail(Class.Range,
+               "register class allocation order must contain distinct members of the same class");
+          return false;
+        }
+        Normalized.AllocationOrder.push_back(Register->second);
+      }
+      if ((Normalized.Allocatable && Normalized.AllocationOrder.empty()) ||
+          (!Normalized.Allocatable && !Normalized.AllocationOrder.empty())) {
+        fail(Class.Range, "allocatable register classes require an allocation order and "
+                          "nonallocatable classes forbid one");
+        return false;
+      }
+      Result.RegisterClasses.push_back(std::move(Normalized));
+    }
+    for (NormalizedRegisterBank &Bank : Result.RegisterBanks) {
+      for (const NormalizedRegisterClass &Class : Result.RegisterClasses) {
+        if (Class.BankID == Bank.ID)
+          Bank.RegisterClasses.push_back(Class.ID);
+      }
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool normalizeRegisterMasks(NormalizedTargetModel &Result) {
+    std::unordered_set<std::string> Names;
+    for (const SourceRegisterMask &Mask : Input.RegisterMasks) {
+      if (Mask.Name.empty() || !Names.insert(Mask.Name).second) {
+        fail(Mask.Range, "register mask names must be nonempty and unique");
+        return false;
+      }
+      NormalizedRegisterMask Normalized{.Name = Mask.Name, .PreservedRegisters = {}};
+      std::unordered_set<std::uint32_t> Preserved;
+      for (const std::string &Symbol : Mask.PreservedRegisterSymbols) {
+        const auto Register = RegisterBySymbol.find(Symbol);
+        if (Register == RegisterBySymbol.end() || !Preserved.insert(Register->second).second) {
+          fail(Mask.Range, "register mask entries must name distinct declared registers");
+          return false;
+        }
+        Normalized.PreservedRegisters.push_back(Register->second);
+      }
+      Result.RegisterMasks.push_back(std::move(Normalized));
+    }
+    return true;
+  }
+
+  const DescriptionAST &Input;
+  std::string SourceName;
+  std::unordered_map<std::string, std::uint32_t> UnitBySymbol;
+  std::unordered_map<std::string, std::uint32_t> RegisterBySymbol;
+  std::unordered_map<std::string, std::uint32_t> BankBySymbol;
+  std::unordered_map<std::string, std::uint32_t> ClassBySymbol;
+  std::vector<TextDiagnostic> Diagnostics;
+};
+
+[[nodiscard]] const NormalizedRegister &findRegister(const NormalizedTargetModel &Model,
+                                                     std::uint32_t ID) {
+  const auto Position = std::ranges::find(Model.Registers, ID, &NormalizedRegister::ID);
+  return *Position;
+}
+
+[[nodiscard]] const SourceRegisterUnit &findRegisterUnit(const NormalizedTargetModel &Model,
+                                                         std::uint32_t ID) {
+  const auto Position = std::ranges::find(Model.RegisterUnits, ID, &SourceRegisterUnit::ID);
+  return *Position;
+}
+
+[[nodiscard]] const NormalizedRegisterBank &findRegisterBank(const NormalizedTargetModel &Model,
+                                                             std::uint32_t ID) {
+  const auto Position = std::ranges::find(Model.RegisterBanks, ID, &NormalizedRegisterBank::ID);
+  return *Position;
+}
+
+[[nodiscard]] std::string emitRegisterHeader(const NormalizedTargetModel &Model,
+                                             std::string_view SourceName) {
+  const std::string Guard = "RCC_TARGET_" + upperIdentifier(Model.Target.Namespace) + "_" +
+                            upperIdentifier(Model.Target.Name) + "REGISTERS_H";
+  std::ostringstream Output;
+  Output << "// SPDX-License-Identifier: GPL-3.0-or-later\n\n";
+  Output << "// This file is generated by rcc-backend-descgen from ";
+  appendQuoted(Output, SourceName);
+  Output << ". Do not edit it manually.\n\n";
+  Output << "#ifndef " << Guard << "\n#define " << Guard << "\n\n";
+  Output << "#include <cstdint>\n#include <string_view>\n\n";
+  Output << "namespace rcc::" << Model.Target.Namespace << " {\n\n";
+  Output << "inline constexpr std::string_view TargetName = ";
+  appendQuoted(Output, Model.Target.Name);
+  Output << ";\ninline constexpr std::string_view TargetTriple = ";
+  appendQuoted(Output, Model.Target.Triple);
+  Output << ";\ninline constexpr std::string_view TargetCPU = ";
+  appendQuoted(Output, Model.Target.CPU);
+  Output << ";\ninline constexpr std::string_view TargetABI = ";
+  appendQuoted(Output, Model.Target.ABI);
+  Output << ";\ninline constexpr std::string_view TargetDataLayout = ";
+  appendQuoted(Output, Model.Target.DataLayout);
+  Output << ";\n\ninline constexpr std::string_view TargetFeatures[] = {\n";
+  for (const std::string &Feature : Model.Target.Features) {
+    Output << "    ";
+    appendQuoted(Output, Feature);
+    Output << ",\n";
+  }
+  Output << "};\n\n";
+
+  Output << "enum class PhysicalRegisterID : std::uint32_t {\n  NoRegister = 0,\n";
+  for (const NormalizedRegister &Register : Model.Registers)
+    Output << "  " << Register.Symbol << " = " << Register.ID << ",\n";
+  Output << "};\n\n";
+  Output << "enum class RegisterUnit : std::uint32_t {\n";
+  for (const SourceRegisterUnit &Unit : Model.RegisterUnits)
+    Output << "  " << Unit.Symbol << " = " << Unit.ID << ",\n";
+  Output << "};\n\n";
+  Output << "enum class RegisterBank : std::uint32_t {\n";
+  for (const NormalizedRegisterBank &Bank : Model.RegisterBanks)
+    Output << "  " << Bank.Symbol << " = " << Bank.ID << ",\n";
+  Output << "};\n\n";
+  Output << "enum class RegisterClass : std::uint32_t {\n";
+  for (const NormalizedRegisterClass &Class : Model.RegisterClasses)
+    Output << "  " << Class.Symbol << " = " << Class.ID << ",\n";
+  Output << "};\n\n";
+  Output << "} // namespace rcc::" << Model.Target.Namespace << "\n\n";
+  Output << "#endif // " << Guard << "\n";
+  return Output.str();
+}
+
+void emitRegisterIDList(std::ostream &Output, const NormalizedTargetModel &Model,
+                        std::span<const std::uint32_t> IDs) {
+  for (const std::uint32_t ID : IDs)
+    Output << "PhysicalRegisterID::" << findRegister(Model, ID).Symbol << ", ";
+}
+
+[[nodiscard]] std::string emitTargetTables(const NormalizedTargetModel &Model,
+                                           std::string_view SourceName) {
+  std::ostringstream Output;
+  Output << "// SPDX-License-Identifier: GPL-3.0-or-later\n\n";
+  Output << "// This file is generated by rcc-backend-descgen from ";
+  appendQuoted(Output, SourceName);
+  Output << ". Do not edit it manually.\n\n";
+  Output << "void appendGeneratedRegisterInfo(TargetRegisterInfoDesc &Description) {\n";
+  Output << "  Description.RegisterUnits = {\n";
+  for (const SourceRegisterUnit &Unit : Model.RegisterUnits) {
+    Output << "      {RegisterUnitID::fromValue(" << Unit.ID << "), ";
+    appendQuoted(Output, Unit.Name);
+    Output << "},\n";
+  }
+  Output << "  };\n\n  Description.PhysicalRegisters = {\n";
+  for (const NormalizedRegister &Register : Model.Registers) {
+    Output << "      {physical(PhysicalRegisterID::" << Register.Symbol << "), ";
+    appendQuoted(Output, Register.Name);
+    Output << ", " << Register.Encoding << ", {";
+    for (const NormalizedRegisterUnitLane &Unit : Register.Units) {
+      Output << "unitLane(RegisterUnit::" << findRegisterUnit(Model, Unit.UnitID).Symbol << ", "
+             << Unit.Lanes << "), ";
+    }
+    Output << "}, " << (Register.IsConstant ? "true" : "false") << ", "
+           << (Register.IsArtificial ? "true" : "false") << ", "
+           << (Register.IsReserved ? "true" : "false") << ", {";
+    for (const std::string &Alias : Register.AlternativeNames) {
+      appendQuoted(Output, Alias);
+      Output << ", ";
+    }
+    Output << "}},\n";
+  }
+  Output << "  };\n\n  Description.RegisterBanks = {\n";
+  for (const NormalizedRegisterBank &Bank : Model.RegisterBanks) {
+    Output << "      {RegisterBankID::fromValue(" << Bank.ID << "), ";
+    appendQuoted(Output, Bank.Name);
+    Output << ", " << Bank.MaximumSizeInBits << ", {";
+    for (const std::uint32_t ClassID : Bank.RegisterClasses) {
+      const auto Position =
+          std::ranges::find(Model.RegisterClasses, ClassID, &NormalizedRegisterClass::ID);
+      Output << "RegisterClassID::fromValue(" << Position->ID << "), ";
+    }
+    Output << "}},\n";
+  }
+  Output << "  };\n\n  Description.RegisterClasses = {\n";
+  for (const NormalizedRegisterClass &Class : Model.RegisterClasses) {
+    Output << "      registerClass(RegisterClass::" << Class.Symbol << ", ";
+    appendQuoted(Output, Class.Name);
+    Output << ", {";
+    emitRegisterIDList(Output, Model, Class.Registers);
+    Output << "}, {";
+    emitRegisterIDList(Output, Model, Class.AllocationOrder);
+    Output << "}, RegisterBank::" << findRegisterBank(Model, Class.BankID).Symbol << ", "
+           << Class.SizeInBits << ", " << Class.SpillSizeInBits << ", "
+           << Class.SpillAlignmentInBits << ", " << Class.Lanes << ", "
+           << (Class.Allocatable ? "true" : "false") << ", " << Class.CopyCost << "),\n";
+  }
+  Output << "  };\n}\n\n";
+  Output << "void appendGeneratedMIRTextInfo(TargetMIRTextInfoDesc &Description) {\n";
+  Output << "  Description.RegisterMasks = {\n";
+  for (const NormalizedRegisterMask &Mask : Model.RegisterMasks) {
+    Output << "      {";
+    appendQuoted(Output, Mask.Name);
+    Output << ", makePreservedMask({";
+    emitRegisterIDList(Output, Model, Mask.PreservedRegisters);
+    Output << "})},\n";
+  }
+  Output << "  };\n  Description.CFIRegisters = {\n";
+  for (const NormalizedRegister &Register : Model.Registers) {
+    Output << "      {physical(PhysicalRegisterID::" << Register.Symbol << "), "
+           << Register.DwarfRegister << ", true},\n";
+  }
+  Output << "  };\n}\n";
+  return Output.str();
+}
+
+} // namespace
+
+DescriptionGenerationResult generateDescription(std::string SourceName, std::string SourceText) {
+  yaml::ParseResult YAMLResult = yaml::parse(SourceName, SourceText);
+  if (!YAMLResult.succeeded()) {
+    DescriptionGenerationResult Result;
+    for (const TextDiagnostic &Diagnostic : YAMLResult.diagnostics())
+      Result.Diagnostics.push_back(Diagnostic);
+    return Result;
+  }
+
+  ASTParser Parser(*YAMLResult.stream());
+  const auto AST = Parser.parse();
+  if (!AST) {
+    DescriptionGenerationResult Result;
+    Result.Diagnostics = Parser.takeDiagnostics();
+    return Result;
+  }
+
+  ModelNormalizer Normalizer(*AST, SourceName);
+  const auto Model = Normalizer.normalize();
+  if (!Model) {
+    DescriptionGenerationResult Result;
+    Result.Diagnostics = Normalizer.takeDiagnostics();
+    return Result;
+  }
+
+  const std::size_t Separator = SourceName.find_last_of("/\\");
+  const std::string_view DisplayName = Separator == std::string::npos
+                                           ? std::string_view(SourceName)
+                                           : std::string_view(SourceName).substr(Separator + 1);
+  return {
+      .Output =
+          GeneratedDescription{
+              .RegisterHeader = emitRegisterHeader(*Model, DisplayName),
+              .TargetTables = emitTargetTables(*Model, DisplayName),
+          },
+      .Diagnostics = {},
+  };
+}
+
+} // namespace rcc::targetgen
diff --git a/backend/lib/Target/Description/TargetDescriptionGenerator.h b/backend/lib/Target/Description/TargetDescriptionGenerator.h
new file mode 100644
index 0000000..54cbf3c
--- /dev/null
+++ b/backend/lib/Target/Description/TargetDescriptionGenerator.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_TARGET_DESCRIPTION_TARGETDESCRIPTIONGENERATOR_H
+#define RCC_TARGET_DESCRIPTION_TARGETDESCRIPTIONGENERATOR_H
+
+#include "rcc/Support/TextDiagnostic.h"
+
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace rcc::targetgen {
+
+struct GeneratedDescription final {
+  std::string RegisterHeader;
+  std::string TargetTables;
+};
+
+struct DescriptionGenerationResult final {
+  std::optional<GeneratedDescription> Output;
+  std::vector<TextDiagnostic> Diagnostics;
+
+  [[nodiscard]] bool succeeded() const noexcept {
+    return Output.has_value() && Diagnostics.empty();
+  }
+};
+
+[[nodiscard]] DescriptionGenerationResult generateDescription(std::string SourceName,
+                                                              std::string SourceText);
+
+} // namespace rcc::targetgen
+
+#endif // RCC_TARGET_DESCRIPTION_TARGETDESCRIPTIONGENERATOR_H