[CodeGen] Align MIR parser and printer ownership

1 files changed, 2967 insertions, 0 deletions

diff --git a/backend/lib/CodeGen/MIRParser/MIParser.cpp b/backend/lib/CodeGen/MIRParser/MIParser.cpp
new file mode 100644
index 0000000..e38b9f1
--- /dev/null
+++ b/backend/lib/CodeGen/MIRParser/MIParser.cpp
@@ -0,0 +1,2967 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/MIRParser/MIParser.h"
+
+#include "MILexer.h"
+#include "rcc/CodeGen/GenericOpcodes.h"
+#include "rcc/CodeGen/InlineAsm.h"
+#include "rcc/CodeGen/InstructionDescriptor.h"
+#include "rcc/CodeGen/MIRYamlMapping.h"
+#include "rcc/CodeGen/MachineBasicBlock.h"
+#include "rcc/CodeGen/MachineCFGUpdater.h"
+#include "rcc/CodeGen/MachineFunction.h"
+#include "rcc/CodeGen/MachineInstr.h"
+#include "rcc/CodeGen/MachineOperand.h"
+#include "rcc/CodeGen/MachineRegisterInfo.h"
+#include "rcc/CodeGen/MachineVerifier.h"
+#include "rcc/CodeGen/TargetDescription.h"
+#include "rcc/CodeGen/TargetMIRTextInfo.h"
+#include "rcc/CodeGen/TargetRegisterInfo.h"
+#include "rcc/MIR/LLVMConstantSyntax.h"
+
+#include <algorithm>
+#include <array>
+#include <bit>
+#include <charconv>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <optional>
+#include <span>
+#include <string>
+#include <string_view>
+#include <system_error>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+namespace rcc::mir {
+namespace {
+
+[[nodiscard]] bool parseUnsignedDecimal(std::string_view Spelling, std::uint64_t &Value) {
+  if (Spelling.empty() || Spelling.front() == '-')
+    return false;
+  const char *Begin = Spelling.data();
+  const char *End = Begin + Spelling.size();
+  const auto Result = std::from_chars(Begin, End, Value, 10);
+  return Result.ec == std::errc{} && Result.ptr == End;
+}
+
+[[nodiscard]] bool parseSignedDecimal(std::string_view Spelling, std::int64_t &Value) {
+  if (Spelling.empty())
+    return false;
+  const char *Begin = Spelling.data();
+  const char *End = Begin + Spelling.size();
+  const auto Result = std::from_chars(Begin, End, Value, 10);
+  return Result.ec == std::errc{} && Result.ptr == End;
+}
+
+[[nodiscard]] bool parseHexadecimal(std::string_view Spelling, std::uint64_t &Value) {
+  if (Spelling.size() < 3 || Spelling[0] != '0' || (Spelling[1] != 'x' && Spelling[1] != 'X'))
+    return false;
+  const char *Begin = Spelling.data() + 2;
+  const char *End = Spelling.data() + Spelling.size();
+  const auto Result = std::from_chars(Begin, End, Value, 16);
+  return Result.ec == std::errc{} && Result.ptr == End;
+}
+
+[[nodiscard]] bool parseUnsignedDigits(std::string_view Spelling, std::uint64_t &Value) {
+  if (Spelling.empty())
+    return false;
+  const char *Begin = Spelling.data();
+  const char *End = Begin + Spelling.size();
+  const auto Result = std::from_chars(Begin, End, Value, 10);
+  return Result.ec == std::errc{} && Result.ptr == End;
+}
+
+[[nodiscard]] std::optional<FloatSemantics> floatSemanticsForKeyword(std::string_view Keyword) {
+  if (Keyword == "half")
+    return FloatSemantics::IEEEHalf;
+  if (Keyword == "bfloat")
+    return FloatSemantics::BFloat;
+  if (Keyword == "float")
+    return FloatSemantics::IEEESingle;
+  if (Keyword == "double")
+    return FloatSemantics::IEEEDouble;
+  if (Keyword == "x86_fp80")
+    return FloatSemantics::X87DoubleExtended;
+  if (Keyword == "fp128")
+    return FloatSemantics::IEEEQuad;
+  if (Keyword == "ppc_fp128")
+    return FloatSemantics::PPCDoubleDouble;
+  return std::nullopt;
+}
+
+[[nodiscard]] bool isFloatingSemanticsKeyword(const MIToken &Token) {
+  return Token.kind() == MITokenKind::Keyword &&
+         floatSemanticsForKeyword(Token.stringValue()).has_value();
+}
+
+[[nodiscard]] bool isCFIOperationToken(const MIToken &Token) {
+  return Token.isKeyword("same_value") || Token.isKeyword("remember_state") ||
+         Token.isKeyword("restore_state") || Token.isKeyword("offset") ||
+         Token.isKeyword("llvm_def_aspace_cfa") || Token.isKeyword("def_cfa_register") ||
+         Token.isKeyword("def_cfa_offset") || Token.isKeyword("def_cfa") ||
+         Token.isKeyword("rel_offset") || Token.isKeyword("adjust_cfa_offset") ||
+         Token.isKeyword("escape") || Token.isKeyword("restore") || Token.isKeyword("undefined") ||
+         Token.isKeyword("register") || Token.isKeyword("window_save") ||
+         Token.isKeyword("negate_ra_sign_state") ||
+         Token.isKeyword("negate_ra_sign_state_with_pc") || Token.isKeyword("llvm_register_pair") ||
+         Token.isKeyword("llvm_vector_registers") || Token.isKeyword("llvm_vector_offset") ||
+         Token.isKeyword("llvm_vector_register_mask");
+}
+
+[[nodiscard]] Expected<IntegerImmediate> parseIntegerImmediateValue(std::uint32_t BitWidth,
+                                                                    std::string_view Spelling) {
+  if (BitWidth == 0 || BitWidth > IntegerImmediate::MaxBitWidth)
+    return makeUnexpected(ErrorCode::ParseError, "typed integer width is out of range");
+
+  const bool Negative = Spelling.starts_with('-');
+  if (Negative)
+    Spelling.remove_prefix(1);
+  if (Spelling.empty())
+    return makeUnexpected(ErrorCode::ParseError, "typed integer has no digits");
+
+  std::vector<std::uint64_t> Words((static_cast<std::size_t>(BitWidth) + 63U) / 64U, 0);
+  for (char Character : Spelling) {
+    if (Character < '0' || Character > '9')
+      return makeUnexpected(ErrorCode::ParseError, "typed integer contains a non-decimal digit");
+    std::uint64_t Carry = static_cast<unsigned>(Character - '0');
+    for (std::uint64_t &Word : Words) {
+      const unsigned __int128 Product = static_cast<unsigned __int128>(Word) * 10U + Carry;
+      Word = static_cast<std::uint64_t>(Product);
+      Carry = static_cast<std::uint64_t>(Product >> 64U);
+    }
+  }
+
+  // LLVM parses the arbitrary-precision literal first and then truncates it to
+  // the declared integer width.  Keep exactly that modulo-2^N bit pattern.
+  if (BitWidth % 64U != 0)
+    Words.back() &= (std::uint64_t{1} << (BitWidth % 64U)) - 1U;
+  if (Negative) {
+    for (std::uint64_t &Word : Words)
+      Word = ~Word;
+    std::uint64_t Carry = 1;
+    for (std::uint64_t &Word : Words) {
+      const std::uint64_t Previous = Word;
+      Word += Carry;
+      Carry = Carry != 0 && Word < Previous ? 1 : 0;
+    }
+    if (BitWidth % 64U != 0)
+      Words.back() &= (std::uint64_t{1} << (BitWidth % 64U)) - 1U;
+  }
+  return IntegerImmediate::create(BitWidth, Words);
+}
+
+[[nodiscard]] std::optional<std::uint64_t> minimumTypeSizeInBits(LLT Type) noexcept {
+  if (!Type.isValid() || Type.isToken())
+    return std::nullopt;
+  const std::uint64_t ScalarSize = Type.scalarBitWidth();
+  if (!Type.isVector())
+    return ScalarSize;
+  const std::uint64_t ElementCount = Type.minimumElementCount();
+  if (ScalarSize != 0 && ElementCount > std::numeric_limits<std::uint64_t>::max() / ScalarSize)
+    return std::nullopt;
+  return ScalarSize * ElementCount;
+}
+
+[[nodiscard]] std::optional<AtomicOrdering> atomicOrdering(std::string_view Name) noexcept {
+  if (Name == "unordered")
+    return AtomicOrdering::Unordered;
+  if (Name == "monotonic")
+    return AtomicOrdering::Monotonic;
+  if (Name == "acquire")
+    return AtomicOrdering::Acquire;
+  if (Name == "release")
+    return AtomicOrdering::Release;
+  if (Name == "acq_rel")
+    return AtomicOrdering::AcquireRelease;
+  if (Name == "seq_cst")
+    return AtomicOrdering::SequentiallyConsistent;
+  return std::nullopt;
+}
+
+[[nodiscard]] bool isInstructionFlag(const MIToken &Token) {
+  return Token.isKeyword("frame-setup") || Token.isKeyword("frame-destroy") ||
+         Token.isKeyword("nnan") || Token.isKeyword("ninf") || Token.isKeyword("nsz") ||
+         Token.isKeyword("arcp") || Token.isKeyword("contract") || Token.isKeyword("afn") ||
+         Token.isKeyword("reassoc") || Token.isKeyword("nuw") || Token.isKeyword("nsw") ||
+         Token.isKeyword("nusw") || Token.isKeyword("exact") || Token.isKeyword("nofpexcept") ||
+         Token.isKeyword("unpredictable") || Token.isKeyword("noconvergent") ||
+         Token.isKeyword("nneg") || Token.isKeyword("disjoint") || Token.isKeyword("samesign") ||
+         Token.isKeyword("inbounds");
+}
+
+[[nodiscard]] std::optional<MachineInstrFlag> instructionFlag(std::string_view Name) {
+  if (Name == "frame-setup")
+    return MachineInstrFlag::FrameSetup;
+  if (Name == "frame-destroy")
+    return MachineInstrFlag::FrameDestroy;
+  if (Name == "nnan")
+    return MachineInstrFlag::FastMathNoNaNs;
+  if (Name == "ninf")
+    return MachineInstrFlag::FastMathNoInfs;
+  if (Name == "nsz")
+    return MachineInstrFlag::FastMathNoSignedZeros;
+  if (Name == "arcp")
+    return MachineInstrFlag::FastMathAllowReciprocal;
+  if (Name == "contract")
+    return MachineInstrFlag::FastMathAllowContract;
+  if (Name == "afn")
+    return MachineInstrFlag::FastMathApproxFunc;
+  if (Name == "reassoc")
+    return MachineInstrFlag::FastMathAllowReassoc;
+  if (Name == "nuw")
+    return MachineInstrFlag::NoUnsignedWrap;
+  if (Name == "nsw")
+    return MachineInstrFlag::NoSignedWrap;
+  if (Name == "nusw")
+    return MachineInstrFlag::NoUSWrap;
+  if (Name == "exact")
+    return MachineInstrFlag::Exact;
+  if (Name == "nofpexcept")
+    return MachineInstrFlag::NoFPExcept;
+  if (Name == "unpredictable")
+    return MachineInstrFlag::Unpredictable;
+  if (Name == "noconvergent")
+    return MachineInstrFlag::NoConvergent;
+  if (Name == "nneg")
+    return MachineInstrFlag::NonNeg;
+  if (Name == "disjoint")
+    return MachineInstrFlag::Disjoint;
+  if (Name == "samesign")
+    return MachineInstrFlag::SameSign;
+  if (Name == "inbounds")
+    return MachineInstrFlag::InBounds;
+  return std::nullopt;
+}
+
+[[nodiscard]] std::optional<IntegerPredicate> integerPredicate(std::string_view Name) {
+  if (Name == "eq")
+    return IntegerPredicate::Equal;
+  if (Name == "ne")
+    return IntegerPredicate::NotEqual;
+  if (Name == "sgt")
+    return IntegerPredicate::SignedGreaterThan;
+  if (Name == "sge")
+    return IntegerPredicate::SignedGreaterEqual;
+  if (Name == "slt")
+    return IntegerPredicate::SignedLessThan;
+  if (Name == "sle")
+    return IntegerPredicate::SignedLessEqual;
+  if (Name == "ugt")
+    return IntegerPredicate::UnsignedGreaterThan;
+  if (Name == "uge")
+    return IntegerPredicate::UnsignedGreaterEqual;
+  if (Name == "ult")
+    return IntegerPredicate::UnsignedLessThan;
+  if (Name == "ule")
+    return IntegerPredicate::UnsignedLessEqual;
+  return std::nullopt;
+}
+
+[[nodiscard]] std::optional<FloatingPredicate> floatingPredicate(std::string_view Name) {
+  if (Name == "false")
+    return FloatingPredicate::AlwaysFalse;
+  if (Name == "oeq")
+    return FloatingPredicate::OrderedEqual;
+  if (Name == "ogt")
+    return FloatingPredicate::OrderedGreaterThan;
+  if (Name == "oge")
+    return FloatingPredicate::OrderedGreaterEqual;
+  if (Name == "olt")
+    return FloatingPredicate::OrderedLessThan;
+  if (Name == "ole")
+    return FloatingPredicate::OrderedLessEqual;
+  if (Name == "one")
+    return FloatingPredicate::OrderedNotEqual;
+  if (Name == "ord")
+    return FloatingPredicate::Ordered;
+  if (Name == "uno")
+    return FloatingPredicate::Unordered;
+  if (Name == "ueq")
+    return FloatingPredicate::UnorderedEqual;
+  if (Name == "ugt")
+    return FloatingPredicate::UnorderedGreaterThan;
+  if (Name == "uge")
+    return FloatingPredicate::UnorderedGreaterEqual;
+  if (Name == "ult")
+    return FloatingPredicate::UnorderedLessThan;
+  if (Name == "ule")
+    return FloatingPredicate::UnorderedLessEqual;
+  if (Name == "une")
+    return FloatingPredicate::UnorderedNotEqual;
+  if (Name == "true")
+    return FloatingPredicate::AlwaysTrue;
+  return std::nullopt;
+}
+
+} // namespace
+
+class MIParser::Impl final {
+public:
+  Impl(MachineFunction &Function, const TargetDescription &Target, std::string SourceName,
+       std::string SourceText, MIParserContext Context, MIParserOptions Options)
+      : Function(Function), Target(Target),
+        Lexer(std::move(SourceName), std::move(SourceText),
+              MILexerOptions{.MaximumTokenLength = Options.MaximumTokenLength,
+                             .MaximumTokens = Options.MaximumTokens}),
+        Context(std::move(Context)), Options(Options) {}
+
+  [[nodiscard]] Expected<void> parse();
+
+  [[nodiscard]] const TextSource &source() const noexcept {
+    return Lexer.source();
+  }
+
+  [[nodiscard]] std::span<const TextDiagnostic> diagnostics() const noexcept {
+    return Diagnostics;
+  }
+
+  [[nodiscard]] bool failed() const noexcept {
+    return !Diagnostics.empty();
+  }
+
+private:
+  struct ParsedOperand final {
+    MachineOperand Operand;
+    std::optional<std::size_t> TiedDef;
+    TextRange Range;
+  };
+
+  [[nodiscard]] const MIToken &token() const noexcept {
+    return Tokens[Position];
+  }
+
+  [[nodiscard]] bool at(MITokenKind Kind) const noexcept {
+    return token().is(Kind);
+  }
+
+  [[nodiscard]] bool nextIs(MITokenKind Kind) const noexcept {
+    return Position + 1U < Tokens.size() && Tokens[Position + 1U].is(Kind);
+  }
+
+  [[nodiscard]] bool atKeyword(std::string_view Keyword) const noexcept {
+    return token().isKeyword(Keyword);
+  }
+
+  void advance() noexcept {
+    if (!at(MITokenKind::EndOfFile))
+      ++Position;
+  }
+
+  [[nodiscard]] bool consume(MITokenKind Kind) noexcept {
+    if (!at(Kind))
+      return false;
+    advance();
+    return true;
+  }
+
+  [[nodiscard]] bool expect(MITokenKind Kind, std::string_view Description);
+  [[nodiscard]] bool fail(const MIToken &At, std::string Message);
+  [[nodiscard]] bool fail(std::string Message) {
+    return fail(token(), std::move(Message));
+  }
+  [[nodiscard]] Expected<void> failureResult() const;
+  [[nodiscard]] bool importError(const MIToken &At, const Error &Failure);
+  [[nodiscard]] bool tokenize();
+
+  [[nodiscard]] bool parseUnsigned(const MIToken &Token, std::uint64_t &Value);
+  [[nodiscard]] bool parseUnsigned32(const MIToken &Token, std::uint32_t &Value);
+  [[nodiscard]] bool parseSigned64(const MIToken &Token, std::int64_t &Value);
+  [[nodiscard]] bool parseOptionalOffset(std::int64_t &Offset);
+  [[nodiscard]] bool parseAlignment(Alignment &Result);
+  [[nodiscard]] bool parseLowLevelType(LLT &Result);
+  [[nodiscard]] bool parseScalarLowLevelType(const MIToken &Token, LLT &Result);
+
+  [[nodiscard]] bool parseFirstPass();
+  [[nodiscard]] bool parseSecondPass();
+  [[nodiscard]] bool parseBlockDefinition(bool Create, std::uint32_t &ID);
+  [[nodiscard]] bool parseBlockAttributes(MachineBasicBlock *Block);
+  [[nodiscard]] bool parseBlockLiveIns(MachineBasicBlock &Block);
+  [[nodiscard]] bool parseBlockSuccessors(MachineBasicBlock &Block);
+  [[nodiscard]] bool parseInstruction(MachineBasicBlock &Block, bool InBundle,
+                                      MachineInstr *PreviousInstruction, MachineInstr *&Result);
+  [[nodiscard]] bool inferSuccessors();
+
+  [[nodiscard]] bool parseRegister(Register &Result);
+  [[nodiscard]] bool parseRegisterOperand(bool IsDef, ParsedOperand &Result);
+  [[nodiscard]] bool parseTargetFlags(std::uint32_t &Flags);
+  [[nodiscard]] bool parseOperand(bool IsDef, ParsedOperand &Result);
+  [[nodiscard]] bool parseInlineAsmExtraInfoOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseInlineAsmOperandFlag(ParsedOperand &Result);
+  [[nodiscard]] bool parseTypedIntegerOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseFloatingImmediateOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseMetadataReference(MachineMetadataReference &Result);
+  [[nodiscard]] bool parseMetadataOperand(ParsedOperand &Result);
+  [[nodiscard]] bool
+  parseInlineDILocation(std::vector<MachineDILocationFrame> &InlineChain,
+                        std::optional<MachineMetadataReference> &TerminalInlinedAt);
+  [[nodiscard]] bool parseCFIRegister(DwarfRegisterNumber &Result);
+  [[nodiscard]] bool parseCFISigned(std::int64_t &Result);
+  [[nodiscard]] bool parseCFIUnsigned(std::uint32_t &Result);
+  [[nodiscard]] bool parseCFIOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseMemoryBase(MemoryBase &Result, std::int64_t &Offset);
+  [[nodiscard]] bool parseMemoryOperand(const MachineMemOperand *&Result, Opcode InstructionOpcode);
+  [[nodiscard]] bool parsePredicateOperand(ParsedOperand &Result, bool IsFloating);
+  [[nodiscard]] bool parseShuffleMaskOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseDebugInstrRefOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseLaneMaskOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseIntrinsicOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseTargetIndexOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseLiveOutMaskOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseCustomMaskOperand(ParsedOperand &Result);
+  [[nodiscard]] bool parseBlockAddressOperand(ParsedOperand &Result);
+
+  [[nodiscard]] Register getOrCreateVirtualRegister(const MIToken &Token);
+  [[nodiscard]] MachineBasicBlock *blockFor(const MIToken &Token);
+  [[nodiscard]] std::optional<FrameIndex> frameIndexFor(const MIToken &Token, bool Fixed);
+  [[nodiscard]] std::optional<ConstantPoolIndex> constantPoolIndexFor(const MIToken &Token);
+  [[nodiscard]] std::optional<JumpTableIndex> jumpTableIndexFor(const MIToken &Token);
+  [[nodiscard]] std::string symbolName(const MIToken &Token) const;
+
+  MachineFunction &Function;
+  const TargetDescription &Target;
+  MILexer Lexer;
+  MIParserContext Context;
+  MIParserOptions Options;
+  std::vector<MIToken> Tokens;
+  std::size_t Position = 0;
+  std::vector<TextDiagnostic> Diagnostics;
+  std::unordered_map<std::uint32_t, MachineBasicBlock *> Blocks;
+  std::unordered_map<std::uint32_t, Register> NumericVirtualRegisters;
+  std::unordered_map<std::string, Register> NamedVirtualRegisters;
+  std::unordered_set<MachineBasicBlock *> ExplicitSuccessorBlocks;
+  std::size_t ParsedInstructionCount = 0;
+  bool ParseAttempted = false;
+};
+
+bool MIParser::Impl::expect(MITokenKind Kind, std::string_view Description) {
+  if (consume(Kind))
+    return false;
+  return fail("expected " + std::string(Description) + ", found " +
+              std::string(getMITokenKindName(token().kind())));
+}
+
+bool MIParser::Impl::fail(const MIToken &At, std::string Message) {
+  if (Diagnostics.empty()) {
+    Diagnostics.push_back(TextDiagnostic{
+        .Severity = DiagnosticSeverity::Error,
+        .Category = "mir-parser",
+        .Message = std::move(Message),
+        .SourceName = std::string(Lexer.source().name()),
+        .Range = At.range(),
+    });
+  }
+  return true;
+}
+
+Expected<void> MIParser::Impl::failureResult() const {
+  const std::string Message =
+      Diagnostics.empty() ? "machine instruction parsing failed" : Diagnostics.front().Message;
+  return makeUnexpected(ErrorCode::ParseError, Message);
+}
+
+bool MIParser::Impl::importError(const MIToken &At, const Error &Failure) {
+  return fail(At, std::string(Failure.message()));
+}
+
+bool MIParser::Impl::tokenize() {
+  while (true) {
+    MIToken Token = Lexer.next();
+    const MITokenKind Kind = Token.kind();
+    Tokens.push_back(std::move(Token));
+    if (Kind == MITokenKind::Error) {
+      const auto LexerDiagnostics = Lexer.diagnostics();
+      Diagnostics.assign(LexerDiagnostics.begin(), LexerDiagnostics.end());
+      return true;
+    }
+    if (Kind == MITokenKind::EndOfFile)
+      return false;
+  }
+}
+
+bool MIParser::Impl::parseUnsigned(const MIToken &Token, std::uint64_t &Value) {
+  if (Token.kind() == MITokenKind::HexLiteral)
+    return !parseHexadecimal(Token.spelling(), Value);
+  if (Token.hasIntegerValue())
+    return !parseUnsignedDecimal(Token.integerValue(), Value);
+  return true;
+}
+
+bool MIParser::Impl::parseUnsigned32(const MIToken &Token, std::uint32_t &Value) {
+  std::uint64_t Wide = 0;
+  if (parseUnsigned(Token, Wide) || Wide > std::numeric_limits<std::uint32_t>::max())
+    return true;
+  Value = static_cast<std::uint32_t>(Wide);
+  return false;
+}
+
+bool MIParser::Impl::parseSigned64(const MIToken &Token, std::int64_t &Value) {
+  if (Token.kind() != MITokenKind::IntegerLiteral)
+    return true;
+  if (parseSignedDecimal(Token.integerValue(), Value))
+    return false;
+  std::uint64_t Unsigned = 0;
+  if (!parseUnsignedDecimal(Token.integerValue(), Unsigned))
+    return true;
+  Value = std::bit_cast<std::int64_t>(Unsigned);
+  return false;
+}
+
+bool MIParser::Impl::parseOptionalOffset(std::int64_t &Offset) {
+  Offset = 0;
+  if (!at(MITokenKind::Plus) && !at(MITokenKind::Minus))
+    return false;
+  const bool Negative = at(MITokenKind::Minus);
+  advance();
+  std::uint64_t Magnitude = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Magnitude) ||
+      Magnitude > (std::uint64_t{1} << 63U)) {
+    return fail("expected a 64-bit integer offset");
+  }
+  if (Negative) {
+    if (Magnitude == (std::uint64_t{1} << 63U))
+      Offset = std::numeric_limits<std::int64_t>::min();
+    else
+      Offset = -static_cast<std::int64_t>(Magnitude);
+  } else {
+    if (Magnitude > static_cast<std::uint64_t>(std::numeric_limits<std::int64_t>::max()))
+      return fail("positive offset exceeds signed 64-bit range");
+    Offset = static_cast<std::int64_t>(Magnitude);
+  }
+  advance();
+  return false;
+}
+
+bool MIParser::Impl::parseAlignment(Alignment &Result) {
+  advance();
+  std::uint64_t Bytes = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Bytes))
+    return fail("expected an unsigned alignment");
+  auto Parsed = Alignment::create(Bytes);
+  if (!Parsed)
+    return importError(token(), Parsed.error());
+  Result = *Parsed;
+  advance();
+  return false;
+}
+
+bool MIParser::Impl::parseScalarLowLevelType(const MIToken &TypeToken, LLT &Result) {
+  if (TypeToken.kind() != MITokenKind::Identifier)
+    return fail(TypeToken, "expected a scalar low-level type");
+  std::string_view Spelling = TypeToken.stringValue();
+  enum class ScalarKind : std::uint8_t {
+    Any,
+    Integer,
+    Float,
+    BFloat,
+    Pointer,
+  };
+  ScalarKind Kind = ScalarKind::Any;
+  std::string_view Digits;
+  if (Spelling.starts_with("bf")) {
+    Kind = ScalarKind::BFloat;
+    Digits = Spelling.substr(2);
+  } else if (Spelling.starts_with('s')) {
+    Kind = ScalarKind::Any;
+    Digits = Spelling.substr(1);
+  } else if (Spelling.starts_with('i')) {
+    Kind = ScalarKind::Integer;
+    Digits = Spelling.substr(1);
+  } else if (Spelling.starts_with('f')) {
+    Kind = ScalarKind::Float;
+    Digits = Spelling.substr(1);
+  } else if (Spelling.starts_with('p')) {
+    Kind = ScalarKind::Pointer;
+    Digits = Spelling.substr(1);
+  } else {
+    return fail(TypeToken, "unknown scalar low-level type '" + std::string(Spelling) + "'");
+  }
+
+  std::uint64_t Value = 0;
+  if (!parseUnsignedDigits(Digits, Value))
+    return fail(TypeToken, "expected integers after 's'/'i'/'f'/'bf'/'p' type identifier");
+
+  Expected<LLT> Created = makeUnexpected(ErrorCode::ParseError, "invalid low-level type");
+  switch (Kind) {
+  case ScalarKind::Any:
+    if (Value == 0) {
+      Result = LLT::token();
+      return false;
+    }
+    Created = LLT::makeAnyScalar(Value);
+    break;
+  case ScalarKind::Integer:
+    Created = LLT::makeInteger(Value);
+    break;
+  case ScalarKind::Float: {
+    std::optional<FloatSemantics> Semantics;
+    if (Value == 16)
+      Semantics = FloatSemantics::IEEEHalf;
+    else if (Value == 32)
+      Semantics = FloatSemantics::IEEESingle;
+    else if (Value == 64)
+      Semantics = FloatSemantics::IEEEDouble;
+    else if (Value == 128)
+      Semantics = FloatSemantics::IEEEQuad;
+    if (!Semantics)
+      return fail(TypeToken, "unsupported IEEE floating low-level type width");
+    Created = LLT::makeFloat(*Semantics);
+    break;
+  }
+  case ScalarKind::BFloat:
+    if (Value != 16)
+      return fail(TypeToken, "bfloat low-level type must have width 16");
+    Created = LLT::makeFloat(FloatSemantics::BFloat);
+    break;
+  case ScalarKind::Pointer:
+    if (!Context.PointerSizeInBits)
+      return fail(TypeToken, "pointer low-level type requires an explicit pointer size");
+    if (auto PointerSize = Context.PointerSizeInBits(static_cast<std::uint32_t>(Value)))
+      Created = LLT::makePointer(Value, *PointerSize);
+    else
+      return importError(TypeToken, PointerSize.error());
+    break;
+  }
+  if (!Created)
+    return importError(TypeToken, Created.error());
+  Result = *Created;
+  return false;
+}
+
+bool MIParser::Impl::parseLowLevelType(LLT &Result) {
+  const MIToken Begin = token();
+  const auto HasScalarPrefix = [](std::string_view Spelling) {
+    return Spelling.starts_with('s') || Spelling.starts_with('i') || Spelling.starts_with('f') ||
+           Spelling.starts_with("bf") || Spelling.starts_with('p');
+  };
+  if (at(MITokenKind::Identifier)) {
+    if (!HasScalarPrefix(token().stringValue())) {
+      return fail(Begin, "expected tN, pA, <M x tN>, <M x pA>, <vscale x M x tN>, or "
+                         "<vscale x M x pA> for GlobalISel type, where t = {'s', 'i', 'f', 'bf'}");
+    }
+    if (parseScalarLowLevelType(token(), Result))
+      return true;
+    advance();
+    return false;
+  }
+  if (!consume(MITokenKind::Less)) {
+    return fail(Begin, "expected tN, pA, <M x tN>, <M x pA>, <vscale x M x tN>, or "
+                       "<vscale x M x pA> for GlobalISel type, where t = {'s', 'i', 'f', 'bf'}");
+  }
+
+  bool Scalable = false;
+  if (at(MITokenKind::Identifier) && token().stringValue() == "vscale") {
+    Scalable = true;
+    advance();
+    if (!at(MITokenKind::Identifier) || token().stringValue() != "x") {
+      return fail("expected <vscale x M x tN>, where t = {'s', 'i', 'f', 'bf', 'p'}");
+    }
+    advance();
+  }
+
+  const auto VectorError = [this, &Begin, Scalable] {
+    if (Scalable) {
+      return fail(Begin, "expected <vscale x M x tN> for vector type, where t = "
+                         "{'s', 'i', 'f', 'bf', 'p'}");
+    }
+    return fail(Begin, "expected <M x tN> for vector type, where t = {'s', 'i', 'f', 'bf', 'p'}");
+  };
+
+  std::uint64_t ElementCount = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), ElementCount))
+    return VectorError();
+  advance();
+  if (!at(MITokenKind::Identifier) || token().stringValue() != "x")
+    return VectorError();
+  advance();
+
+  if (!at(MITokenKind::Identifier) || !HasScalarPrefix(token().stringValue()))
+    return VectorError();
+  LLT ElementType;
+  if (parseScalarLowLevelType(token(), ElementType))
+    return true;
+  if (ElementType.isToken())
+    return fail("token cannot be a vector element type");
+  advance();
+  if (!consume(MITokenKind::Greater))
+    return VectorError();
+
+  Expected<LLT> Created = Scalable ? LLT::makeScalableVector(ElementCount, ElementType)
+                                   : LLT::makeFixedVector(ElementCount, ElementType);
+  if (!Created)
+    return importError(Begin, Created.error());
+  Result = *Created;
+  return false;
+}
+
+bool MIParser::Impl::parseBlockAttributes(MachineBasicBlock *Block) {
+  std::unordered_set<std::string> Seen;
+  while (!at(MITokenKind::RightParen)) {
+    const MIToken AttributeToken = token();
+    if (atKeyword("machine-block-address-taken") || atKeyword("landing-pad") ||
+        atKeyword("inlineasm-br-indirect-target") || atKeyword("ehfunclet-entry") ||
+        atKeyword("ehscope-entry")) {
+      const std::string Name(AttributeToken.stringValue());
+      if (!Seen.insert(Name).second)
+        return fail("duplicate basic block attribute '" + Name + "'");
+      if (Block != nullptr) {
+        if (Name == "machine-block-address-taken")
+          Block->attributes().set(MachineBasicBlockAttribute::MachineBlockAddressTaken);
+        else if (Name == "landing-pad")
+          Block->attributes().set(MachineBasicBlockAttribute::LandingPad);
+        else if (Name == "inlineasm-br-indirect-target")
+          Block->attributes().set(MachineBasicBlockAttribute::InlineAsmBrIndirectTarget);
+        else if (Name == "ehfunclet-entry")
+          Block->attributes().set(MachineBasicBlockAttribute::EHFuncletEntry);
+        else
+          Block->attributes().set(MachineBasicBlockAttribute::EHScopeEntry);
+      }
+      advance();
+    } else if (atKeyword("ir-block-address-taken")) {
+      if (!Seen.insert("ir-block-address-taken").second)
+        return fail("duplicate basic block attribute 'ir-block-address-taken'");
+      advance();
+      if (!at(MITokenKind::IRBlock) && !at(MITokenKind::NamedIRBlock))
+        return fail("expected an IR block after 'ir-block-address-taken'");
+      if (Block != nullptr) {
+        Block->attributes().set(MachineBasicBlockAttribute::IRBlockAddressTaken);
+        auto SetName = Block->attributes().setIRBlockName(symbolName(token()));
+        if (!SetName)
+          return importError(token(), SetName.error());
+      }
+      advance();
+    } else if (at(MITokenKind::IRBlock) || at(MITokenKind::NamedIRBlock)) {
+      if (!Seen.insert("ir-block").second)
+        return fail("duplicate IR block attribute");
+      if (Context.HasIRBlock && !Context.HasIRBlock(symbolName(token())))
+        return fail(token(), "use of undefined IR block '" + std::string(token().spelling()) + "'");
+      if (Block != nullptr) {
+        auto SetName = Block->attributes().setIRBlockName(symbolName(token()));
+        if (!SetName)
+          return importError(token(), SetName.error());
+      }
+      advance();
+    } else if (atKeyword("align")) {
+      if (!Seen.insert("align").second)
+        return fail("duplicate basic block alignment");
+      Alignment Align;
+      if (parseAlignment(Align))
+        return true;
+      if (Block != nullptr)
+        Block->attributes().setAlignment(Align);
+    } else if (atKeyword("bbsections")) {
+      if (!Seen.insert("bbsections").second)
+        return fail("duplicate basic block section");
+      advance();
+      MachineBasicBlockSectionID Section;
+      std::uint32_t Number = 0;
+      if (at(MITokenKind::IntegerLiteral) && !parseUnsigned32(token(), Number))
+        Section = MachineBasicBlockSectionID::numbered(Number);
+      else if (at(MITokenKind::Identifier) && token().stringValue() == "Exception")
+        Section = MachineBasicBlockSectionID::exception();
+      else if (at(MITokenKind::Identifier) && token().stringValue() == "Cold")
+        Section = MachineBasicBlockSectionID::cold();
+      else
+        return fail("unknown basic block section ID");
+      if (Block != nullptr)
+        Block->attributes().setSectionID(Section);
+      advance();
+    } else if (atKeyword("bb_id")) {
+      if (!Seen.insert("bb_id").second)
+        return fail("duplicate basic block profile ID");
+      advance();
+      std::uint32_t BaseID = 0;
+      std::uint32_t CloneID = 0;
+      if (at(MITokenKind::FloatingPointLiteral)) {
+        const std::string_view Spelling = token().spelling();
+        const std::size_t Dot = Spelling.find('.');
+        std::uint64_t Base = 0;
+        std::uint64_t Clone = 0;
+        if (Dot == std::string_view::npos || !parseUnsignedDecimal(Spelling.substr(0, Dot), Base) ||
+            !parseUnsignedDecimal(Spelling.substr(Dot + 1), Clone) ||
+            Base > std::numeric_limits<std::uint32_t>::max() ||
+            Clone > std::numeric_limits<std::uint32_t>::max()) {
+          return fail("invalid basic block profile ID");
+        }
+        BaseID = static_cast<std::uint32_t>(Base);
+        CloneID = static_cast<std::uint32_t>(Clone);
+        advance();
+      } else {
+        if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), BaseID))
+          return fail("invalid basic block base ID");
+        advance();
+        if (consume(MITokenKind::Dot) || consume(MITokenKind::Comma)) {
+          if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), CloneID))
+            return fail("invalid basic block clone ID");
+          advance();
+        }
+      }
+      if (Block != nullptr)
+        Block->attributes().setProfileID({BaseID, CloneID});
+    } else if (atKeyword("call-frame-size")) {
+      if (!Seen.insert("call-frame-size").second)
+        return fail("duplicate basic block call frame size");
+      advance();
+      std::uint32_t Size = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), Size))
+        return fail("invalid basic block call frame size");
+      if (Block != nullptr)
+        Block->attributes().setCallFrameSize(Size);
+      advance();
+    } else {
+      return fail("unknown basic block attribute '" + std::string(token().spelling()) + "'");
+    }
+
+    if (!consume(MITokenKind::Comma))
+      break;
+  }
+  return expect(MITokenKind::RightParen, "')'");
+}
+
+bool MIParser::Impl::parseBlockDefinition(bool Create, std::uint32_t &ID) {
+  const MIToken Label = token();
+  if (!at(MITokenKind::MachineBasicBlockLabel) || parseUnsigned32(Label, ID))
+    return fail("invalid machine basic block label");
+  advance();
+
+  MachineBasicBlock *Block = nullptr;
+  if (Create) {
+    if (Blocks.size() >= Options.MaximumBlocks)
+      return fail(Label, "machine basic block count exceeds parser limit");
+    if (Blocks.contains(ID))
+      return fail(Label, "redefinition of machine basic block with id #" + std::to_string(ID));
+    if (!Label.stringValue().empty() && Context.HasIRBlock &&
+        !Context.HasIRBlock(Label.stringValue())) {
+      return fail(Label, "basic block '" + std::string(Label.stringValue()) +
+                             "' is not defined in the function '" + std::string(Function.name()) +
+                             "'");
+    }
+    auto Created = Function.createBasicBlock();
+    if (!Created)
+      return importError(Label, Created.error());
+    Block = *Created;
+    auto Appended = Function.appendBlock(*Block);
+    if (!Appended)
+      return importError(Label, Appended.error());
+    if (!Label.stringValue().empty()) {
+      auto SetName = Block->attributes().setName(std::string(Label.stringValue()));
+      if (!SetName)
+        return importError(Label, SetName.error());
+    }
+    Blocks.emplace(ID, Block);
+  } else {
+    const auto Found = Blocks.find(ID);
+    if (Found == Blocks.end())
+      return fail(Label, "use of undefined machine basic block #" + std::to_string(ID));
+    Block = Found->second;
+  }
+
+  if (consume(MITokenKind::LeftParen) && parseBlockAttributes(Create ? Block : nullptr))
+    return true;
+  return expect(MITokenKind::Colon, "':' after the basic block definition");
+}
+
+bool MIParser::Impl::parseFirstPass() {
+  Position = 0;
+  bool AtLineStart = true;
+  std::size_t BraceDepth = 0;
+  while (!at(MITokenKind::EndOfFile)) {
+    if (consume(MITokenKind::Newline)) {
+      AtLineStart = true;
+      continue;
+    }
+    if (at(MITokenKind::MachineBasicBlockLabel)) {
+      if (!AtLineStart || token().range().Begin.Column != 1)
+        return fail("basic block definition must be at the start of a line");
+      std::uint32_t ID = 0;
+      if (parseBlockDefinition(true, ID))
+        return true;
+      AtLineStart = false;
+      continue;
+    }
+    if (at(MITokenKind::LeftBrace))
+      ++BraceDepth;
+    else if (at(MITokenKind::RightBrace)) {
+      if (BraceDepth == 0)
+        return fail("extraneous closing instruction bundle brace");
+      --BraceDepth;
+    }
+    AtLineStart = false;
+    advance();
+  }
+  if (BraceDepth != 0)
+    return fail("unterminated instruction bundle");
+  return false;
+}
+
+Register MIParser::Impl::getOrCreateVirtualRegister(const MIToken &Token) {
+  if (Token.kind() == MITokenKind::VirtualRegister) {
+    std::uint32_t ID = 0;
+    if (parseUnsigned32(Token, ID))
+      return {};
+    if (const auto Found = NumericVirtualRegisters.find(ID);
+        Found != NumericVirtualRegisters.end()) {
+      return Found->second;
+    }
+    auto Created = Function.registerInfo().createVirtualRegister();
+    if (!Created) {
+      static_cast<void>(importError(Token, Created.error()));
+      return {};
+    }
+    NumericVirtualRegisters.emplace(ID, *Created);
+    return *Created;
+  }
+
+  const std::string Name(Token.stringValue());
+  if (const auto Found = NamedVirtualRegisters.find(Name); Found != NamedVirtualRegisters.end())
+    return Found->second;
+  auto Created = Function.registerInfo().createVirtualRegister();
+  if (!Created) {
+    static_cast<void>(importError(Token, Created.error()));
+    return {};
+  }
+  auto Info = Function.registerInfo().virtualRegisterInfo(*Created);
+  if (!Info) {
+    static_cast<void>(importError(Token, Info.error()));
+    return {};
+  }
+  Info->get().Name = Name;
+  NamedVirtualRegisters.emplace(Name, *Created);
+  return *Created;
+}
+
+bool MIParser::Impl::parseRegister(Register &Result) {
+  const MIToken RegisterToken = token();
+  if (consume(MITokenKind::Underscore)) {
+    Result = {};
+    return false;
+  }
+  if (at(MITokenKind::NamedRegister)) {
+    if (RegisterToken.stringValue() == "noreg") {
+      Result = {};
+      advance();
+      return false;
+    }
+    const PhysicalRegisterDesc *Description =
+        Target.registers().physicalRegister(RegisterToken.stringValue());
+    if (Description == nullptr)
+      return fail("unknown physical register '$" + std::string(RegisterToken.stringValue()) + "'");
+    Result = Register::fromPhysical(Description->Reg);
+    advance();
+    return false;
+  }
+  if (at(MITokenKind::VirtualRegister) || at(MITokenKind::NamedVirtualRegister)) {
+    Result = getOrCreateVirtualRegister(RegisterToken);
+    if (Result.isNoRegister())
+      return true;
+    advance();
+    return false;
+  }
+  return fail("expected a machine register");
+}
+
+bool MIParser::Impl::parseRegisterOperand(bool IsDef, ParsedOperand &Result) {
+  const MIToken Begin = token();
+  RegisterOperandFlags Flags{IsDef ? RegisterOperandFlag::Define : RegisterOperandFlag::Use};
+  std::unordered_set<std::string> SeenFlags;
+  while (token().isRegisterFlag()) {
+    const std::string Name(token().stringValue());
+    if (!SeenFlags.insert(Name).second)
+      return fail("duplicate '" + Name + "' register flag");
+    if (Name == "implicit")
+      Flags.set(RegisterOperandFlag::Implicit);
+    else if (Name == "implicit-def") {
+      Flags.clear(RegisterOperandFlag::Use);
+      Flags.set(RegisterOperandFlag::Define);
+      Flags.set(RegisterOperandFlag::Implicit);
+      IsDef = true;
+    } else if (Name == "def") {
+      Flags.clear(RegisterOperandFlag::Use);
+      Flags.set(RegisterOperandFlag::Define);
+      IsDef = true;
+    } else if (Name == "dead")
+      Flags.set(RegisterOperandFlag::Dead);
+    else if (Name == "killed")
+      Flags.set(RegisterOperandFlag::Kill);
+    else if (Name == "undef")
+      Flags.set(RegisterOperandFlag::Undef);
+    else if (Name == "internal")
+      Flags.set(RegisterOperandFlag::InternalRead);
+    else if (Name == "early-clobber")
+      Flags.set(RegisterOperandFlag::EarlyClobber);
+    else if (Name == "debug-use")
+      Flags.set(RegisterOperandFlag::Debug);
+    else if (Name == "renamable")
+      Flags.set(RegisterOperandFlag::Renamable);
+    advance();
+  }
+
+  Register Reg;
+  if (parseRegister(Reg))
+    return true;
+
+  SubRegIndex SubReg;
+  if (consume(MITokenKind::Dot)) {
+    if (!Reg.isVirtual() || !at(MITokenKind::Identifier))
+      return fail("subregister index requires a virtual register");
+    const SubRegIndexDesc *Description = Target.registers().subRegIndex(token().stringValue());
+    if (Description == nullptr)
+      return fail("unknown subregister index '" + std::string(token().stringValue()) + "'");
+    SubReg = Description->ID;
+    advance();
+  }
+
+  if (consume(MITokenKind::Colon)) {
+    if (!Reg.isVirtual())
+      return fail("register class or bank requires a virtual register");
+    auto InfoResult = Function.registerInfo().virtualRegisterInfo(Reg);
+    if (!InfoResult)
+      return importError(Begin, InfoResult.error());
+    VirtualRegisterInfo &Info = InfoResult->get();
+    if (consume(MITokenKind::Underscore)) {
+      if (Info.RegClass || Info.Bank)
+        return fail("conflicting generic virtual register constraint");
+    } else if (at(MITokenKind::Identifier)) {
+      if (const RegisterClassDesc *Class =
+              Target.registers().registerClass(token().stringValue())) {
+        if ((Info.RegClass && *Info.RegClass != Class->ID) ||
+            (Info.Bank && *Info.Bank != Class->DefaultBank))
+          return fail("conflicting virtual register class");
+        auto SetClass = Function.registerInfo().setRegisterClass(Reg, Class->ID);
+        if (!SetClass)
+          return importError(token(), SetClass.error());
+        auto SetBank = Function.registerInfo().setRegisterBank(Reg, Class->DefaultBank);
+        if (!SetBank)
+          return importError(token(), SetBank.error());
+      } else if (const RegisterBankDesc *Bank =
+                     Target.registers().registerBank(token().stringValue())) {
+        const RegisterClassDesc *ExistingClass =
+            Info.RegClass ? Target.registers().registerClass(*Info.RegClass) : nullptr;
+        if ((Info.Bank && *Info.Bank != Bank->ID) ||
+            (Info.RegClass && (ExistingClass == nullptr || ExistingClass->DefaultBank != Bank->ID)))
+          return fail("conflicting virtual register bank");
+        auto SetBank = Function.registerInfo().setRegisterBank(Reg, Bank->ID);
+        if (!SetBank)
+          return importError(token(), SetBank.error());
+      } else {
+        return fail("unknown register class or bank '" + std::string(token().stringValue()) + "'");
+      }
+      advance();
+    } else {
+      return fail("expected '_', register class, or register bank name");
+    }
+  }
+
+  std::optional<std::size_t> TiedDef;
+  if (consume(MITokenKind::LeftParen)) {
+    if (atKeyword("tied-def")) {
+      if (IsDef)
+        return fail("'tied-def' is only valid on register uses");
+      advance();
+      std::uint64_t Index = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Index) ||
+          Index > std::numeric_limits<std::size_t>::max()) {
+        return fail("invalid tied-def operand index");
+      }
+      TiedDef = static_cast<std::size_t>(Index);
+      advance();
+      if (expect(MITokenKind::RightParen, "')' after tied-def"))
+        return true;
+    } else {
+      if (!Reg.isVirtual())
+        return fail("low-level type is only valid on a virtual register");
+      LLT Type;
+      if (parseLowLevelType(Type))
+        return true;
+      if (expect(MITokenKind::RightParen, "')' after the low-level type"))
+        return true;
+      auto InfoResult = Function.registerInfo().virtualRegisterInfo(Reg);
+      if (!InfoResult)
+        return importError(Begin, InfoResult.error());
+      VirtualRegisterInfo &Info = InfoResult->get();
+      if (Info.Type && *Info.Type != Type)
+        return fail(Begin, "conflicting virtual register low-level type");
+      auto SetType = Function.registerInfo().setType(Reg, Type);
+      if (!SetType)
+        return importError(Begin, SetType.error());
+    }
+  }
+
+  if (IsDef && Reg.isVirtual()) {
+    auto InfoResult = Function.registerInfo().virtualRegisterInfo(Reg);
+    if (!InfoResult)
+      return importError(Begin, InfoResult.error());
+    const VirtualRegisterInfo &Info = InfoResult->get();
+    if (!Info.RegClass && !Info.Type)
+      return fail(Begin, "generic virtual register definition requires a low-level type");
+  }
+
+  if (Flags.has(RegisterOperandFlag::Define) && Flags.has(RegisterOperandFlag::Kill))
+    return fail(Begin, "defined register operand cannot be killed");
+  if (!Flags.has(RegisterOperandFlag::Define) && Flags.has(RegisterOperandFlag::Dead))
+    return fail(Begin, "register use cannot be dead");
+
+  auto Operand = MachineOperand::registerOperand(Reg, Flags, SubReg);
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result =
+      ParsedOperand{std::move(*Operand), TiedDef, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+MachineBasicBlock *MIParser::Impl::blockFor(const MIToken &Token) {
+  std::uint32_t ID = 0;
+  if (parseUnsigned32(Token, ID)) {
+    static_cast<void>(fail(Token, "invalid machine basic block reference"));
+    return nullptr;
+  }
+  const auto Found = Blocks.find(ID);
+  if (Found == Blocks.end()) {
+    static_cast<void>(fail(Token, "use of undefined machine basic block #" + std::to_string(ID)));
+    return nullptr;
+  }
+  if (!Token.stringValue().empty()) {
+    const std::optional<std::string_view> Name = Found->second->attributes().name();
+    if (!Name || *Name != Token.stringValue()) {
+      static_cast<void>(fail(Token, "machine basic block reference has a mismatched name"));
+      return nullptr;
+    }
+  }
+  return Found->second;
+}
+
+std::optional<FrameIndex> MIParser::Impl::frameIndexFor(const MIToken &Token, bool Fixed) {
+  std::uint32_t ID = 0;
+  if (parseUnsigned32(Token, ID)) {
+    static_cast<void>(fail(Token, "invalid stack object reference"));
+    return std::nullopt;
+  }
+  const auto &Slots = Fixed ? Context.FixedStackObjects : Context.StackObjects;
+  for (const MIFrameObjectSlot &Slot : Slots) {
+    if (Slot.TextID != ID)
+      continue;
+    if (!Token.stringValue().empty() && (!Slot.Name || *Slot.Name != Token.stringValue())) {
+      static_cast<void>(fail(Token, "stack object reference has a mismatched name"));
+      return std::nullopt;
+    }
+    if (Function.frameInfo().object(Slot.Index) == nullptr) {
+      static_cast<void>(fail(Token, "stack object slot maps to a missing frame object"));
+      return std::nullopt;
+    }
+    return Slot.Index;
+  }
+  static_cast<void>(fail(Token, std::string("use of undefined ") +
+                                    (Fixed ? "fixed stack" : "stack") + " object #" +
+                                    std::to_string(ID)));
+  return std::nullopt;
+}
+
+std::optional<ConstantPoolIndex> MIParser::Impl::constantPoolIndexFor(const MIToken &Token) {
+  std::uint32_t ID = 0;
+  if (parseUnsigned32(Token, ID)) {
+    static_cast<void>(fail(Token, "invalid constant pool reference"));
+    return std::nullopt;
+  }
+  for (const MIConstantPoolSlot &Slot : Context.ConstantPoolItems) {
+    if (Slot.TextID == ID && Function.constantPool().entry(Slot.Index) != nullptr)
+      return Slot.Index;
+  }
+  static_cast<void>(fail(Token, "use of undefined constant pool item #" + std::to_string(ID)));
+  return std::nullopt;
+}
+
+std::optional<JumpTableIndex> MIParser::Impl::jumpTableIndexFor(const MIToken &Token) {
+  std::uint32_t ID = 0;
+  if (parseUnsigned32(Token, ID)) {
+    static_cast<void>(fail(Token, "invalid jump table reference"));
+    return std::nullopt;
+  }
+  for (const MIJumpTableSlot &Slot : Context.JumpTables) {
+    if (Slot.TextID == ID && (Function.jumpTableInfo().table(Slot.Index) != nullptr ||
+                              (Slot.Index.value() < Function.jumpTableInfo().tables().size() &&
+                               Function.jumpTableInfo().tables()[Slot.Index.value()].isPending())))
+      return Slot.Index;
+  }
+  static_cast<void>(fail(Token, "use of undefined jump table #" + std::to_string(ID)));
+  return std::nullopt;
+}
+
+std::string MIParser::Impl::symbolName(const MIToken &Token) const {
+  if (Token.hasStringValue())
+    return std::string(Token.stringValue());
+  return std::string(Token.integerValue());
+}
+
+bool MIParser::Impl::parseTargetFlags(std::uint32_t &Flags) {
+  Flags = 0;
+  if (!atKeyword("target-flags"))
+    return false;
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after target-flags"))
+    return true;
+  if (!at(MITokenKind::Identifier))
+    return fail("expected a target flag name");
+
+  const std::string First(token().stringValue());
+  if (const auto Direct = Target.mirText().directOperandFlag(First))
+    Flags = *Direct;
+  else if (const auto Bit = Target.mirText().bitmaskOperandFlag(First))
+    Flags = *Bit;
+  else
+    return fail("unknown target operand flag '" + First + "'");
+  advance();
+
+  std::unordered_set<std::string> Seen{First};
+  while (consume(MITokenKind::Comma)) {
+    if (!at(MITokenKind::Identifier))
+      return fail("expected a target bit flag name");
+    const std::string Name(token().stringValue());
+    const auto Bit = Target.mirText().bitmaskOperandFlag(Name);
+    if (!Bit)
+      return fail("unknown target bit operand flag '" + Name + "'");
+    if (!Seen.insert(Name).second || (Flags & *Bit) == *Bit)
+      return fail("duplicate target operand flag '" + Name + "'");
+    Flags |= *Bit;
+    advance();
+  }
+  if (expect(MITokenKind::RightParen, "')' after target flags"))
+    return true;
+  const auto Valid = Target.mirText().validateOperandFlags(Flags);
+  return !Valid && importError(token(), Valid.error());
+}
+
+bool MIParser::Impl::parseTypedIntegerOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  const std::string_view TypeSpelling = Begin.stringValue();
+  if (!TypeSpelling.starts_with('i'))
+    return fail(Begin, "typed integer operand must use an 'iN' type");
+  std::uint64_t WideBitWidth = 0;
+  if (!parseUnsignedDigits(TypeSpelling.substr(1), WideBitWidth) ||
+      WideBitWidth > IntegerImmediate::MaxBitWidth) {
+    return fail(Begin, "typed integer operand has an invalid bit width");
+  }
+  const auto BitWidth = static_cast<std::uint32_t>(WideBitWidth);
+  advance();
+
+  std::string_view ValueSpelling;
+  if (at(MITokenKind::IntegerLiteral)) {
+    ValueSpelling = token().integerValue();
+  } else if (at(MITokenKind::Identifier) && token().stringValue() == "true") {
+    ValueSpelling = "1";
+  } else if (at(MITokenKind::Identifier) && token().stringValue() == "false") {
+    ValueSpelling = "0";
+  } else {
+    return fail("expected a decimal integer, true, or false after the typed integer type");
+  }
+
+  auto Value = parseIntegerImmediateValue(BitWidth, ValueSpelling);
+  if (!Value)
+    return importError(token(), Value.error());
+  advance();
+  Result = ParsedOperand{
+      MachineOperand::integerImmediate(std::move(*Value)),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseFloatingImmediateOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  const auto Semantics = floatSemanticsForKeyword(Begin.stringValue());
+  if (!Semantics)
+    return fail(Begin, "unknown floating-point immediate type");
+  advance();
+  if (!at(MITokenKind::FloatingPointLiteral) && !at(MITokenKind::HexLiteral))
+    return fail("expected a floating-point literal");
+
+  const MIToken Literal = token();
+  std::string ConstantText(Begin.stringValue());
+  ConstantText.push_back(' ');
+  ConstantText.append(Literal.spelling());
+  auto Constant = parseLLVMConstant(ConstantText);
+  if (!Constant)
+    return fail(Literal, std::string(Constant.error().message()));
+  if (!Constant->FloatingValue || Constant->FloatingValue->semantics() != *Semantics)
+    return fail(Literal, "floating-point literal produced the wrong semantics");
+  advance();
+  Result = ParsedOperand{
+      MachineOperand::floatingImmediate(*Constant->FloatingValue),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseMetadataReference(MachineMetadataReference &Result) {
+  const MIToken Begin = token();
+  if (expect(MITokenKind::Exclaim, "'!' before a metadata slot"))
+    return true;
+  std::uint32_t TextID = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), TextID))
+    return fail("expected a 32-bit metadata slot number");
+
+  for (const MIMetadataSlot &Slot : Context.Metadata) {
+    if (Slot.TextID != TextID)
+      continue;
+    if (!Slot.Reference.isValid())
+      return fail(Begin, "metadata slot maps to an invalid reference");
+    Result = Slot.Reference;
+    advance();
+    return false;
+  }
+  if (Function.metadata().node(TextID) != nullptr) {
+    Result = MachineMetadataReference::machineFunction(TextID);
+    advance();
+    return false;
+  }
+  return fail(Begin, "use of undefined metadata slot !" + std::to_string(TextID));
+}
+
+bool MIParser::Impl::parseMetadataOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  MachineMetadataValue Value;
+  if (at(MITokenKind::Exclaim)) {
+    MachineMetadataReference Reference;
+    if (parseMetadataReference(Reference))
+      return true;
+    auto Created = MachineMetadataValue::reference(Reference);
+    if (!Created)
+      return importError(Begin, Created.error());
+    Value = std::move(*Created);
+  } else if (at(MITokenKind::MetadataKeyword) && token().isMetadataKeyword("!DIExpression")) {
+    advance();
+    if (expect(MITokenKind::LeftParen, "'(' after !DIExpression"))
+      return true;
+    std::vector<std::uint64_t> Elements;
+    while (!at(MITokenKind::RightParen)) {
+      if (at(MITokenKind::Identifier)) {
+        const auto Opcode = parseDIExpressionOpcodeName(token().stringValue());
+        const auto Encoding = parseDIExpressionAttributeEncodingName(token().stringValue());
+        if (!Opcode && !Encoding)
+          return fail(invalidDIExpressionElementMessage(token().stringValue()));
+        Elements.push_back(Opcode ? *Opcode : *Encoding);
+        advance();
+      } else if (at(MITokenKind::IntegerLiteral)) {
+        std::int64_t Signed = 0;
+        if (parseSigned64(token(), Signed))
+          return fail("debug expression element exceeds 64 bits");
+        Elements.push_back(std::bit_cast<std::uint64_t>(Signed));
+        advance();
+      } else {
+        return fail("expected a debug expression opcode or integer");
+      }
+      if (!consume(MITokenKind::Comma))
+        break;
+    }
+    if (expect(MITokenKind::RightParen, "')' after !DIExpression"))
+      return true;
+    Value = MachineMetadataValue::expression(MachineDIExpression(std::move(Elements)));
+  } else {
+    return fail("expected a metadata reference or !DIExpression");
+  }
+
+  auto Operand = MachineOperand::metadata(std::move(Value));
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseInlineDILocation(
+    std::vector<MachineDILocationFrame> &InlineChain,
+    std::optional<MachineMetadataReference> &TerminalInlinedAt) {
+  if (!at(MITokenKind::MetadataKeyword) || !token().isMetadataKeyword("!DILocation")) {
+    return fail("expected an inline !DILocation");
+  }
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after !DILocation"))
+    return true;
+
+  MachineDILocationFrame Frame;
+  bool HasLine = false;
+  bool HasScope = false;
+  std::vector<MachineDILocationFrame> NestedChain;
+  std::optional<MachineMetadataReference> NestedTerminal;
+  std::unordered_set<std::string> SeenFields;
+  while (!at(MITokenKind::RightParen)) {
+    if (!at(MITokenKind::Identifier))
+      return fail("expected a DILocation field name");
+    const MIToken FieldToken = token();
+    const std::string Field(token().stringValue());
+    if (!SeenFields.insert(Field).second)
+      return fail("duplicate DILocation field '" + Field + "'");
+    advance();
+    if (expect(MITokenKind::Colon, "':' after a DILocation field name"))
+      return true;
+
+    if (Field == "line") {
+      std::uint32_t Line = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), Line))
+        return fail("expected an unsigned 32-bit DILocation line");
+      Frame.Line = Line;
+      HasLine = true;
+      advance();
+    } else if (Field == "column") {
+      std::uint64_t Column = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Column) ||
+          Column > std::numeric_limits<std::uint16_t>::max()) {
+        return fail("expected an unsigned 16-bit DILocation column");
+      }
+      Frame.Column = static_cast<std::uint16_t>(Column);
+      advance();
+    } else if (Field == "scope") {
+      MachineMetadataReference Scope;
+      if (parseMetadataReference(Scope))
+        return true;
+      if (Scope.scope() != MachineMetadataScope::EmbeddedIR)
+        return fail(FieldToken, "DILocation scope must reference embedded IR metadata");
+      Frame.Scope = Scope;
+      HasScope = true;
+    } else if (Field == "inlinedAt") {
+      if (at(MITokenKind::MetadataKeyword) && token().isMetadataKeyword("!DILocation")) {
+        if (parseInlineDILocation(NestedChain, NestedTerminal))
+          return true;
+      } else {
+        MachineMetadataReference Reference;
+        if (parseMetadataReference(Reference))
+          return true;
+        if (Reference.scope() != MachineMetadataScope::EmbeddedIR) {
+          return fail(FieldToken, "DILocation inlinedAt must reference embedded IR metadata");
+        }
+        NestedTerminal = Reference;
+      }
+    } else if (Field == "isImplicitCode") {
+      if (!at(MITokenKind::Identifier) ||
+          (token().stringValue() != "true" && token().stringValue() != "false")) {
+        return fail("expected 'true' or 'false' for DILocation isImplicitCode");
+      }
+      Frame.IsImplicitCode = token().stringValue() == "true";
+      advance();
+    } else if (Field == "atomGroup") {
+      std::uint64_t Group = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Group) ||
+          Group > MachineDILocation::MaxAtomGroup) {
+        return fail("DILocation atomGroup exceeds 61 bits");
+      }
+      Frame.AtomGroup = Group;
+      advance();
+    } else if (Field == "atomRank") {
+      std::uint64_t Rank = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Rank) || Rank > 7) {
+        return fail("DILocation atomRank exceeds three bits");
+      }
+      Frame.AtomRank = static_cast<std::uint8_t>(Rank);
+      advance();
+    } else {
+      return fail(FieldToken, "unknown DILocation field '" + Field + "'");
+    }
+
+    if (!consume(MITokenKind::Comma))
+      break;
+  }
+  if (expect(MITokenKind::RightParen, "')' after !DILocation"))
+    return true;
+  if (!HasLine)
+    return fail("DILocation requires a line field");
+  if (!HasScope)
+    return fail("DILocation requires a scope field");
+
+  InlineChain.push_back(Frame);
+  InlineChain.insert(InlineChain.end(), NestedChain.begin(), NestedChain.end());
+  TerminalInlinedAt = NestedTerminal;
+  return false;
+}
+
+bool MIParser::Impl::parseCFIRegister(DwarfRegisterNumber &Result) {
+  if (!at(MITokenKind::NamedRegister))
+    return fail("expected a physical register in the CFI instruction");
+  const MIToken RegisterToken = token();
+  Register Reg;
+  if (parseRegister(Reg) || !Reg.isPhysical())
+    return true;
+  const auto Physical = Reg.physicalRegister();
+  if (!Physical)
+    return fail(RegisterToken, "CFI register is not a physical register");
+  const auto Dwarf = Target.mirText().dwarfRegister(*Physical);
+  if (!Dwarf)
+    return fail(RegisterToken, "physical register has no canonical DWARF register number");
+  Result = DwarfRegisterNumber::fromValue(*Dwarf);
+  return false;
+}
+
+bool MIParser::Impl::parseCFISigned(std::int64_t &Result) {
+  if (!at(MITokenKind::IntegerLiteral) || parseSigned64(token(), Result))
+    return fail("expected a signed 64-bit CFI integer");
+  advance();
+  return false;
+}
+
+bool MIParser::Impl::parseCFIUnsigned(std::uint32_t &Result) {
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), Result))
+    return fail("expected an unsigned 32-bit CFI integer");
+  advance();
+  return false;
+}
+
+bool MIParser::Impl::parseCFIOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  const std::string Operation(token().stringValue());
+  advance();
+
+  const auto Comma = [this]() { return expect(MITokenKind::Comma, "',' in CFI instruction"); };
+  DwarfRegisterNumber Register;
+  DwarfRegisterNumber OtherRegister;
+  std::int64_t Offset = 0;
+  std::optional<MachineCFIInstruction> Instruction;
+  if (Operation == "same_value") {
+    if (parseCFIRegister(Register))
+      return true;
+    Instruction = MachineCFIInstruction::sameValue(Register);
+  } else if (Operation == "remember_state") {
+    Instruction = MachineCFIInstruction::rememberState();
+  } else if (Operation == "restore_state") {
+    Instruction = MachineCFIInstruction::restoreState();
+  } else if (Operation == "offset" || Operation == "rel_offset") {
+    if (parseCFIRegister(Register) || Comma() || parseCFISigned(Offset))
+      return true;
+    Instruction = Operation == "offset" ? MachineCFIInstruction::offset(Register, Offset)
+                                        : MachineCFIInstruction::relativeOffset(Register, Offset);
+  } else if (Operation == "def_cfa_register") {
+    if (parseCFIRegister(Register))
+      return true;
+    Instruction = MachineCFIInstruction::defCFARegister(Register);
+  } else if (Operation == "def_cfa_offset" || Operation == "adjust_cfa_offset") {
+    if (parseCFISigned(Offset))
+      return true;
+    Instruction = Operation == "def_cfa_offset" ? MachineCFIInstruction::defCFAOffset(Offset)
+                                                : MachineCFIInstruction::adjustCFAOffset(Offset);
+  } else if (Operation == "def_cfa") {
+    if (parseCFIRegister(Register) || Comma() || parseCFISigned(Offset))
+      return true;
+    Instruction = MachineCFIInstruction::defCFA(Register, Offset);
+  } else if (Operation == "llvm_def_aspace_cfa") {
+    std::uint32_t AddressSpace = 0;
+    if (parseCFIRegister(Register) || Comma() || parseCFISigned(Offset) || Comma() ||
+        parseCFIUnsigned(AddressSpace)) {
+      return true;
+    }
+    Instruction = MachineCFIInstruction::llvmDefAddressSpaceCFA(Register, Offset, AddressSpace);
+  } else if (Operation == "restore" || Operation == "undefined") {
+    if (parseCFIRegister(Register))
+      return true;
+    Instruction = Operation == "restore" ? MachineCFIInstruction::restore(Register)
+                                         : MachineCFIInstruction::undefined(Register);
+  } else if (Operation == "register") {
+    if (parseCFIRegister(Register) || Comma() || parseCFIRegister(OtherRegister))
+      return true;
+    Instruction = MachineCFIInstruction::registerRule(Register, OtherRegister);
+  } else if (Operation == "window_save") {
+    Instruction = MachineCFIInstruction::windowSave();
+  } else if (Operation == "negate_ra_sign_state") {
+    Instruction = MachineCFIInstruction::negateReturnAddressState();
+  } else if (Operation == "negate_ra_sign_state_with_pc") {
+    Instruction = MachineCFIInstruction::negateReturnAddressStateWithPC();
+  } else if (Operation == "llvm_register_pair") {
+    DwarfRegisterNumber First;
+    DwarfRegisterNumber Second;
+    std::uint32_t FirstSize = 0;
+    std::uint32_t SecondSize = 0;
+    if (parseCFIRegister(Register) || Comma() || parseCFIRegister(First) || Comma() ||
+        parseCFIUnsigned(FirstSize) || Comma() || parseCFIRegister(Second) || Comma() ||
+        parseCFIUnsigned(SecondSize)) {
+      return true;
+    }
+    Instruction = MachineCFIInstruction::llvmRegisterPair({.Register = Register,
+                                                           .FirstRegister = First,
+                                                           .FirstSizeInBits = FirstSize,
+                                                           .SecondRegister = Second,
+                                                           .SecondSizeInBits = SecondSize});
+  } else if (Operation == "llvm_vector_registers") {
+    if (parseCFIRegister(Register) || Comma())
+      return true;
+    std::vector<MachineCFIVectorRegisterLane> Registers;
+    do {
+      DwarfRegisterNumber VectorRegister;
+      std::uint32_t Lane = 0;
+      std::uint32_t Size = 0;
+      if (parseCFIRegister(VectorRegister) || Comma() || parseCFIUnsigned(Lane) || Comma() ||
+          parseCFIUnsigned(Size)) {
+        return true;
+      }
+      Registers.push_back({.Register = VectorRegister, .Lane = Lane, .SizeInBits = Size});
+      if (!at(MITokenKind::Comma))
+        break;
+      advance();
+      if (!at(MITokenKind::NamedRegister))
+        return fail("expected another vector CFI register tuple");
+    } while (true);
+    auto Created = MachineCFIInstruction::llvmVectorRegisters(
+        {.Register = Register, .VectorRegisters = std::move(Registers)});
+    if (!Created)
+      return importError(Begin, Created.error());
+    Instruction = std::move(*Created);
+  } else if (Operation == "llvm_vector_offset") {
+    DwarfRegisterNumber MaskRegister;
+    std::uint32_t RegisterSize = 0;
+    std::uint32_t MaskSize = 0;
+    if (parseCFIRegister(Register) || Comma() || parseCFIUnsigned(RegisterSize) || Comma() ||
+        parseCFIRegister(MaskRegister) || Comma() || parseCFIUnsigned(MaskSize) || Comma() ||
+        parseCFISigned(Offset)) {
+      return true;
+    }
+    Instruction = MachineCFIInstruction::llvmVectorOffset({.Register = Register,
+                                                           .RegisterSizeInBits = RegisterSize,
+                                                           .MaskRegister = MaskRegister,
+                                                           .MaskRegisterSizeInBits = MaskSize,
+                                                           .Offset = Offset});
+  } else if (Operation == "llvm_vector_register_mask") {
+    DwarfRegisterNumber SpillRegister;
+    DwarfRegisterNumber MaskRegister;
+    std::uint32_t SpillLaneSize = 0;
+    std::uint32_t MaskSize = 0;
+    if (parseCFIRegister(Register) || Comma() || parseCFIRegister(SpillRegister) || Comma() ||
+        parseCFIUnsigned(SpillLaneSize) || Comma() || parseCFIRegister(MaskRegister) || Comma() ||
+        parseCFIUnsigned(MaskSize)) {
+      return true;
+    }
+    Instruction =
+        MachineCFIInstruction::llvmVectorRegisterMask({.Register = Register,
+                                                       .SpillRegister = SpillRegister,
+                                                       .SpillRegisterLaneSizeInBits = SpillLaneSize,
+                                                       .MaskRegister = MaskRegister,
+                                                       .MaskRegisterSizeInBits = MaskSize});
+  } else if (Operation == "escape") {
+    std::vector<std::uint8_t> Bytes;
+    while (true) {
+      std::uint64_t Byte = 0;
+      if (!at(MITokenKind::HexLiteral) || parseUnsigned(token(), Byte) ||
+          Byte > std::numeric_limits<std::uint8_t>::max()) {
+        return fail("CFI escape element must be an 8-bit hexadecimal literal");
+      }
+      Bytes.push_back(static_cast<std::uint8_t>(Byte));
+      advance();
+      if (!at(MITokenKind::Comma) || !nextIs(MITokenKind::HexLiteral))
+        break;
+      advance();
+    }
+    auto Created = MachineCFIInstruction::escape(std::move(Bytes));
+    if (!Created)
+      return importError(Begin, Created.error());
+    Instruction = std::move(*Created);
+  } else {
+    return fail(Begin, "unsupported CFI operation '" + Operation + "'");
+  }
+
+  auto Index = Function.cfiInfo().addInstruction(std::move(*Instruction));
+  if (!Index)
+    return importError(Begin, Index.error());
+  Result = ParsedOperand{
+      MachineOperand::cfiIndex(*Index),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseMemoryBase(MemoryBase &Result, std::int64_t &Offset) {
+  const MIToken BaseToken = token();
+  switch (BaseToken.kind()) {
+  case MITokenKind::StackObject:
+  case MITokenKind::FixedStackObject: {
+    const auto Index = frameIndexFor(BaseToken, BaseToken.kind() == MITokenKind::FixedStackObject);
+    if (!Index)
+      return true;
+    Result = MemoryBase::frameIndex(*Index);
+    advance();
+    break;
+  }
+  case MITokenKind::ConstantPoolItem: {
+    const auto Index = constantPoolIndexFor(BaseToken);
+    if (!Index)
+      return true;
+    Result = MemoryBase::constantPool(*Index);
+    advance();
+    break;
+  }
+  case MITokenKind::JumpTableIndex: {
+    const auto Index = jumpTableIndexFor(BaseToken);
+    if (!Index)
+      return true;
+    Result = MemoryBase::jumpTable(*Index);
+    advance();
+    break;
+  }
+  case MITokenKind::GlobalValue:
+  case MITokenKind::NamedGlobalValue:
+    Result = MemoryBase::globalSymbol(symbolName(BaseToken));
+    advance();
+    break;
+  case MITokenKind::ExternalSymbol:
+    Result = MemoryBase::externalSymbol(symbolName(BaseToken));
+    advance();
+    break;
+  case MITokenKind::IRValue:
+  case MITokenKind::NamedIRValue:
+    Result = MemoryBase::irValue(symbolName(BaseToken));
+    advance();
+    break;
+  case MITokenKind::QuotedIRValue: {
+    auto Constant = parseLLVMConstant(BaseToken.stringValue());
+    if (!Constant)
+      return importError(BaseToken, Constant.error());
+    auto Base = MemoryBase::irConstant(std::move(*Constant));
+    if (!Base)
+      return importError(BaseToken, Base.error());
+    Result = std::move(*Base);
+    advance();
+    break;
+  }
+  case MITokenKind::Keyword:
+    if (BaseToken.isKeyword("unknown-address")) {
+      Result = MemoryBase();
+      advance();
+    } else if (BaseToken.isKeyword("stack")) {
+      Result = MemoryBase::stack();
+      advance();
+    } else if (BaseToken.isKeyword("got")) {
+      Result = MemoryBase::got();
+      advance();
+    } else if (BaseToken.isKeyword("constant-pool")) {
+      Result = MemoryBase::constantPoolPseudo();
+      advance();
+    } else if (BaseToken.isKeyword("jump-table")) {
+      Result = MemoryBase::jumpTablePseudo();
+      advance();
+    } else if (BaseToken.isKeyword("call-entry")) {
+      advance();
+      if (at(MITokenKind::GlobalValue) || at(MITokenKind::NamedGlobalValue)) {
+        Result = MemoryBase::callEntryGlobal(symbolName(token()));
+      } else if (at(MITokenKind::ExternalSymbol)) {
+        Result = MemoryBase::callEntryExternal(symbolName(token()));
+      } else {
+        return fail("call-entry memory base requires a global or external symbol");
+      }
+      advance();
+    } else if (BaseToken.isKeyword("custom")) {
+      advance();
+      if (!at(MITokenKind::Identifier) && !at(MITokenKind::StringConstant))
+        return fail("custom memory base requires a target spelling");
+      Result = MemoryBase::custom(std::string(token().stringValue()));
+      advance();
+    } else {
+      return fail(BaseToken, "unsupported machine memory base");
+    }
+    break;
+  default:
+    return fail(BaseToken, "expected a machine memory base");
+  }
+  return parseOptionalOffset(Offset);
+}
+
+bool MIParser::Impl::parseMemoryOperand(const MachineMemOperand *&Result,
+                                        Opcode InstructionOpcode) {
+  const MIToken Begin = token();
+  if (expect(MITokenKind::LeftParen, "'(' before a machine memory operand"))
+    return true;
+
+  MachineMemOperandDesc Description;
+  std::unordered_set<std::string> SeenFlags;
+  while (token().isMemoryOperandFlag()) {
+    const std::string Name(token().stringValue());
+    if (!SeenFlags.insert(Name).second)
+      return fail("duplicate machine memory operand flag '" + Name + "'");
+    if (atKeyword("volatile"))
+      Description.Accesses.set(MemoryAccessFlag::Volatile);
+    else if (atKeyword("non-temporal"))
+      Description.Accesses.set(MemoryAccessFlag::NonTemporal);
+    else if (atKeyword("dereferenceable"))
+      Description.Accesses.set(MemoryAccessFlag::Dereferenceable);
+    else if (atKeyword("invariant"))
+      Description.Accesses.set(MemoryAccessFlag::Invariant);
+    else {
+      const auto Flag = Target.mirText().machineMemOperandFlag(token().stringValue());
+      if (!Flag)
+        return fail("unknown target machine memory operand flag '" + Name + "'");
+      if ((Description.TargetFlags & *Flag) != 0)
+        return fail("overlapping target machine memory operand flag '" + Name + "'");
+      Description.TargetFlags |= *Flag;
+    }
+    advance();
+  }
+
+  if (!at(MITokenKind::Identifier) ||
+      (token().stringValue() != "load" && token().stringValue() != "store")) {
+    return fail("expected load or store in a machine memory operand");
+  }
+  if (token().stringValue() == "load")
+    Description.Accesses.set(MemoryAccessFlag::Load);
+  else
+    Description.Accesses.set(MemoryAccessFlag::Store);
+  advance();
+  if (at(MITokenKind::Identifier) && token().stringValue() == "store") {
+    if (Description.Accesses.has(MemoryAccessFlag::Store))
+      return fail("duplicate store memory operation");
+    Description.Accesses.set(MemoryAccessFlag::Store);
+    advance();
+  }
+
+  if (at(MITokenKind::Identifier) && token().stringValue() == "syncscope") {
+    advance();
+    if (expect(MITokenKind::LeftParen, "'(' after syncscope"))
+      return true;
+    if (!at(MITokenKind::StringConstant))
+      return fail("syncscope requires a quoted scope name");
+    const std::string_view Name = token().stringValue();
+    auto Scope = std::ranges::find_if(
+        Context.SyncScopes, [Name](const MISyncScopeSlot &Slot) { return Slot.Name == Name; });
+    if (Scope == Context.SyncScopes.end() && Context.InternSyncScope) {
+      const MIToken NameToken = token();
+      auto ID = Context.InternSyncScope(Name);
+      if (!ID)
+        return importError(NameToken, ID.error());
+      Context.SyncScopes.push_back({.Name = std::string(Name), .ID = *ID});
+      Scope = std::prev(Context.SyncScopes.end());
+    }
+    if (Scope == Context.SyncScopes.end())
+      return fail("unknown synchronization scope '" + std::string(Name) + "'");
+    Description.SyncScope = Scope->ID;
+    advance();
+    if (expect(MITokenKind::RightParen, "')' after syncscope"))
+      return true;
+  }
+
+  std::size_t OrderingCount = 0;
+  while (at(MITokenKind::Identifier)) {
+    const auto Ordering = atomicOrdering(token().stringValue());
+    if (!Ordering)
+      break;
+    if (OrderingCount == 0)
+      Description.SuccessOrdering = *Ordering;
+    else if (OrderingCount == 1)
+      Description.FailureOrdering = *Ordering;
+    else
+      return fail("machine memory operand has more than two atomic orderings");
+    ++OrderingCount;
+    advance();
+  }
+  const bool IsLoad = Description.Accesses.has(MemoryAccessFlag::Load);
+  const bool IsStore = Description.Accesses.has(MemoryAccessFlag::Store);
+  if (OrderingCount == 1) {
+    if (InstructionOpcode == opcode(GenericOpcode::G_ATOMIC_CMPXCHG) ||
+        InstructionOpcode == opcode(GenericOpcode::G_ATOMIC_CMPXCHG_WITH_SUCCESS)) {
+      Description.AtomicKind = AtomicOperation::CompareExchange;
+    } else {
+      Description.AtomicKind = IsLoad && IsStore
+                                   ? AtomicOperation::ReadModifyWrite
+                                   : (IsLoad ? AtomicOperation::Load : AtomicOperation::Store);
+    }
+  } else if (OrderingCount == 2)
+    Description.AtomicKind = AtomicOperation::CompareExchange;
+
+  std::uint64_t MinimumBytes = 0;
+  if (at(MITokenKind::IntegerLiteral)) {
+    if (parseUnsigned(token(), MinimumBytes) || MinimumBytes == 0)
+      return fail("machine memory operand size must be a nonzero byte count");
+    auto Size = MemorySize::fixed(MinimumBytes);
+    if (!Size)
+      return importError(token(), Size.error());
+    Description.Size = *Size;
+    advance();
+  } else if (atKeyword("unknown-size")) {
+    advance();
+  } else if (consume(MITokenKind::LeftParen)) {
+    LLT Type;
+    if (parseLowLevelType(Type))
+      return true;
+    if (expect(MITokenKind::RightParen, "')' after the memory low-level type"))
+      return true;
+    const auto MinimumBits = minimumTypeSizeInBits(Type);
+    if (!MinimumBits || *MinimumBits == 0)
+      return fail(Begin, "memory low-level type has no representable size");
+    MinimumBytes = (*MinimumBits + 7U) / 8U;
+    auto Size = Type.isScalableVector() ? MemorySize::scalable(MinimumBytes)
+                                        : MemorySize::fixed(MinimumBytes);
+    if (!Size)
+      return importError(Begin, Size.error());
+    Description.Size = *Size;
+    Description.MemoryType = Type;
+  } else {
+    return fail("expected a memory size, unknown-size, or memory low-level type");
+  }
+
+  if (MinimumBytes != 0) {
+    if (MinimumBytes > (std::uint64_t{1} << 63U))
+      return fail(Begin, "machine memory operand size has no representable default alignment");
+    auto DefaultAlignment = Alignment::create(std::bit_ceil(MinimumBytes));
+    if (!DefaultAlignment)
+      return importError(Begin, DefaultAlignment.error());
+    Description.Align = *DefaultAlignment;
+  }
+
+  if (at(MITokenKind::Identifier)) {
+    const std::string_view ExpectedPreposition =
+        IsLoad && IsStore ? "on" : (IsLoad ? "from" : "into");
+    if (token().stringValue() != ExpectedPreposition) {
+      return fail("expected '" + std::string(ExpectedPreposition) +
+                  "' before the machine memory base");
+    }
+    advance();
+    if (parseMemoryBase(Description.Base, Description.Offset))
+      return true;
+    if (const GenericConstantData *Constant = Description.Base.constantValue())
+      Description.AddressSpace = Constant->Type.AddressSpace;
+  }
+
+  Alignment BaseAlignment = Description.Align;
+  std::unordered_set<std::string> SeenOptions;
+  while (consume(MITokenKind::Comma)) {
+    const std::string Name(token().spelling());
+    if (!SeenOptions.insert(Name).second)
+      return fail("duplicate machine memory operand option '" + Name + "'");
+    if (atKeyword("align")) {
+      Alignment ParsedAlignment;
+      if (parseAlignment(ParsedAlignment))
+        return true;
+      if ((static_cast<std::uint64_t>(Description.Offset) & (ParsedAlignment.bytes() - 1U)) != 0) {
+        return fail("specified alignment is more aligned than offset");
+      }
+      BaseAlignment = ParsedAlignment;
+    } else if (atKeyword("basealign")) {
+      if (parseAlignment(BaseAlignment))
+        return true;
+    } else if (atKeyword("addrspace")) {
+      advance();
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), Description.AddressSpace) ||
+          Description.AddressSpace > LLT::MaxAddressSpace) {
+        return fail("invalid machine memory operand address space");
+      }
+      advance();
+    } else if (at(MITokenKind::MetadataKeyword)) {
+      const std::string MetadataKind(token().stringValue());
+      advance();
+      MachineMetadataReference Reference;
+      if (parseMetadataReference(Reference))
+        return true;
+      if (MetadataKind == "!tbaa")
+        Description.TBAA = Reference;
+      else if (MetadataKind == "!alias.scope")
+        Description.AliasScope = Reference;
+      else if (MetadataKind == "!noalias")
+        Description.NoAlias = Reference;
+      else if (MetadataKind == "!noalias.addrspace")
+        Description.NoAliasAddressSpace = Reference;
+      else if (MetadataKind == "!range")
+        Description.RangeMetadata = Reference;
+      else
+        return fail("unsupported machine memory operand metadata attachment");
+    } else {
+      return fail("unknown machine memory operand option '" + Name + "'");
+    }
+  }
+
+  std::uint64_t EffectiveAlignment = BaseAlignment.bytes();
+  if (Description.Offset != 0) {
+    const auto OffsetBits = static_cast<std::uint64_t>(Description.Offset);
+    const std::uint64_t OffsetAlignment = std::uint64_t{1} << std::countr_zero(OffsetBits);
+    EffectiveAlignment = std::min(EffectiveAlignment, OffsetAlignment);
+  }
+  Description.Align = *Alignment::create(EffectiveAlignment);
+  if (BaseAlignment != Description.Align)
+    Description.BaseAlign = BaseAlignment;
+  else
+    Description.BaseAlign.reset();
+
+  if (expect(MITokenKind::RightParen, "')' after the machine memory operand"))
+    return true;
+
+  auto Created = Function.createMemOperand(std::move(Description));
+  if (!Created)
+    return importError(Begin, Created.error());
+  Result = *Created;
+  return false;
+}
+
+bool MIParser::Impl::parsePredicateOperand(ParsedOperand &Result, bool IsFloating) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after predicate kind"))
+    return true;
+  if (!at(MITokenKind::Identifier))
+    return fail("expected a predicate spelling");
+
+  Expected<MachineOperand> Operand = IsFloating ? [&]() -> Expected<MachineOperand> {
+    const auto Predicate = floatingPredicate(token().stringValue());
+    if (!Predicate) {
+      return makeUnexpected(ErrorCode::ParseError, "invalid floating-point predicate");
+    }
+    return MachineOperand::floatingPredicate(*Predicate);
+  }()
+      : [&]() -> Expected<MachineOperand> {
+          const auto Predicate = integerPredicate(token().stringValue());
+          if (!Predicate) {
+            return makeUnexpected(ErrorCode::ParseError, "invalid integer predicate");
+          }
+          return MachineOperand::integerPredicate(*Predicate);
+        }();
+  if (!Operand)
+    return importError(token(), Operand.error());
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after predicate"))
+    return true;
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseShuffleMaskOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after shufflemask"))
+    return true;
+  std::vector<std::int32_t> Elements;
+  while (!at(MITokenKind::RightParen)) {
+    if (atKeyword("undef")) {
+      Elements.push_back(ShuffleMaskOperand::Undef);
+      advance();
+    } else {
+      std::int64_t Value = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseSigned64(token(), Value) ||
+          Value < std::numeric_limits<std::int32_t>::min() ||
+          Value > std::numeric_limits<std::int32_t>::max()) {
+        return fail("shuffle mask element must be a 32-bit integer or undef");
+      }
+      Elements.push_back(static_cast<std::int32_t>(Value));
+      advance();
+    }
+    if (!consume(MITokenKind::Comma))
+      break;
+  }
+  if (expect(MITokenKind::RightParen, "')' after shufflemask"))
+    return true;
+  auto Operand = MachineOperand::shuffleMask(std::move(Elements));
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseDebugInstrRefOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after dbg-instr-ref"))
+    return true;
+  std::uint64_t Instruction = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), Instruction))
+    return fail("invalid debug instruction number");
+  advance();
+  if (expect(MITokenKind::Comma, "',' in dbg-instr-ref"))
+    return true;
+  std::uint64_t OperandNumber = 0;
+  if (!at(MITokenKind::IntegerLiteral) || parseUnsigned(token(), OperandNumber))
+    return fail("invalid debug operand number");
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after dbg-instr-ref"))
+    return true;
+  auto Operand = MachineOperand::debugInstrRef(Instruction, OperandNumber);
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseLaneMaskOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after lanemask"))
+    return true;
+  std::uint64_t Value = 0;
+  if (parseUnsigned(token(), Value))
+    return fail("invalid 64-bit lane mask");
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after lanemask"))
+    return true;
+  Result = ParsedOperand{MachineOperand::laneMask(LaneMask::fromRaw(Value)),
+                         std::nullopt,
+                         {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseIntrinsicOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after intrinsic"))
+    return true;
+  if (!at(MITokenKind::NamedGlobalValue))
+    return fail("expected a named intrinsic");
+  const auto ID = Target.mirText().intrinsic(token().stringValue());
+  if (!ID)
+    return fail("unknown intrinsic '" + std::string(token().stringValue()) + "'");
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after intrinsic"))
+    return true;
+  auto Operand = MachineOperand::intrinsic(*ID);
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseTargetIndexOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after target-index"))
+    return true;
+  if (!at(MITokenKind::Identifier))
+    return fail("expected a target index name");
+  const auto Index = Target.mirText().targetIndex(token().stringValue());
+  if (!Index)
+    return fail("unknown target index '" + std::string(token().stringValue()) + "'");
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after target index"))
+    return true;
+  std::int64_t Offset = 0;
+  if (parseOptionalOffset(Offset))
+    return true;
+  Result = ParsedOperand{MachineOperand::targetIndex(*Index, Offset),
+                         std::nullopt,
+                         {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseCustomMaskOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after CustomRegMask"))
+    return true;
+  std::uint32_t MaximumRegister = 0;
+  for (const PhysicalRegisterDesc &Register : Target.registers().physicalRegisters())
+    MaximumRegister = std::max(MaximumRegister, Register.Reg.number());
+  std::vector<std::uint64_t> Words(MaximumRegister / 64U + 1U, 0);
+  if (!at(MITokenKind::RightParen)) {
+    do {
+      Register Reg;
+      if (!at(MITokenKind::NamedRegister) || parseRegister(Reg) || !Reg.isPhysical())
+        return fail("CustomRegMask requires physical registers");
+      const auto Physical = Reg.physicalRegister();
+      if (!Physical)
+        return fail("CustomRegMask requires physical registers");
+      const std::uint32_t Number = Physical->number();
+      Words[Number / 64U] |= std::uint64_t{1} << (Number % 64U);
+    } while (consume(MITokenKind::Comma));
+  }
+  if (expect(MITokenKind::RightParen, "')' after CustomRegMask"))
+    return true;
+  auto Operand =
+      MachineOperand::registerMask(std::make_shared<const RegisterMask>(std::move(Words)));
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseLiveOutMaskOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after liveout"))
+    return true;
+  std::uint32_t MaximumRegister = 0;
+  for (const PhysicalRegisterDesc &Register : Target.registers().physicalRegisters())
+    MaximumRegister = std::max(MaximumRegister, Register.Reg.number());
+  std::vector<std::uint64_t> Words(MaximumRegister / 64U + 1U, 0);
+  do {
+    Register Reg;
+    if (!at(MITokenKind::NamedRegister) || parseRegister(Reg) || !Reg.isPhysical())
+      return fail("liveout requires physical registers");
+    const auto Physical = Reg.physicalRegister();
+    if (!Physical)
+      return fail("liveout requires physical registers");
+    const std::uint32_t Number = Physical->number();
+    Words[Number / 64U] |= std::uint64_t{1} << (Number % 64U);
+  } while (consume(MITokenKind::Comma));
+  if (expect(MITokenKind::RightParen, "')' after liveout"))
+    return true;
+  auto Operand =
+      MachineOperand::liveOutRegisterMask(std::make_shared<const RegisterMask>(std::move(Words)));
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseBlockAddressOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  advance();
+  if (expect(MITokenKind::LeftParen, "'(' after blockaddress"))
+    return true;
+  if (!at(MITokenKind::GlobalValue) && !at(MITokenKind::NamedGlobalValue))
+    return fail("blockaddress requires a function reference");
+  const std::string FunctionName = symbolName(token());
+  advance();
+  if (expect(MITokenKind::Comma, "',' in blockaddress"))
+    return true;
+  if (!at(MITokenKind::IRBlock) && !at(MITokenKind::NamedIRBlock))
+    return fail("blockaddress requires an IR block reference");
+  const std::string BlockName = symbolName(token());
+  advance();
+  if (expect(MITokenKind::RightParen, "')' after blockaddress"))
+    return true;
+  std::int64_t Offset = 0;
+  if (parseOptionalOffset(Offset))
+    return true;
+  auto Operand = MachineOperand::blockAddress(FunctionName, BlockName, Offset);
+  if (!Operand)
+    return importError(Begin, Operand.error());
+  Result = ParsedOperand{
+      std::move(*Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseOperand(bool IsDef, ParsedOperand &Result) {
+  const MIToken Begin = token();
+  if (token().isRegister() || token().isRegisterFlag())
+    return parseRegisterOperand(IsDef, Result);
+
+  std::uint32_t TargetFlags = 0;
+  if (parseTargetFlags(TargetFlags))
+    return true;
+  const MIToken OperandToken = token();
+  if (isFloatingSemanticsKeyword(OperandToken)) {
+    if (parseFloatingImmediateOperand(Result))
+      return true;
+    Result.Operand.setTargetFlags(TargetFlags);
+    return false;
+  }
+  if (OperandToken.kind() == MITokenKind::Exclaim ||
+      (OperandToken.kind() == MITokenKind::MetadataKeyword &&
+       OperandToken.isMetadataKeyword("!DIExpression"))) {
+    if (parseMetadataOperand(Result))
+      return true;
+    Result.Operand.setTargetFlags(TargetFlags);
+    return false;
+  }
+  if (isCFIOperationToken(OperandToken)) {
+    if (parseCFIOperand(Result))
+      return true;
+    Result.Operand.setTargetFlags(TargetFlags);
+    return false;
+  }
+  MachineOperand Operand = MachineOperand::immediate(0);
+  bool HasOperand = true;
+
+  switch (OperandToken.kind()) {
+  case MITokenKind::IntegerLiteral: {
+    std::int64_t Value = 0;
+    if (parseSigned64(OperandToken, Value))
+      return fail("integer literal is too large for a machine immediate");
+    Operand = MachineOperand::immediate(Value, TargetFlags);
+    advance();
+    break;
+  }
+  case MITokenKind::MachineBasicBlock: {
+    MachineBasicBlock *Block = blockFor(OperandToken);
+    if (Block == nullptr)
+      return true;
+    Operand = MachineOperand::basicBlock(*Block, TargetFlags);
+    advance();
+    break;
+  }
+  case MITokenKind::StackObject:
+  case MITokenKind::FixedStackObject: {
+    const bool Fixed = OperandToken.kind() == MITokenKind::FixedStackObject;
+    const auto Index = frameIndexFor(OperandToken, Fixed);
+    if (!Index)
+      return true;
+    advance();
+    std::int64_t Offset = 0;
+    if (parseOptionalOffset(Offset))
+      return true;
+    Operand = MachineOperand::frameIndex(*Index, Offset, TargetFlags);
+    break;
+  }
+  case MITokenKind::ConstantPoolItem: {
+    const auto Index = constantPoolIndexFor(OperandToken);
+    if (!Index)
+      return true;
+    advance();
+    std::int64_t Offset = 0;
+    if (parseOptionalOffset(Offset))
+      return true;
+    Operand = MachineOperand::constantPool(*Index, Offset, TargetFlags);
+    break;
+  }
+  case MITokenKind::JumpTableIndex: {
+    const auto Index = jumpTableIndexFor(OperandToken);
+    if (!Index)
+      return true;
+    Operand = MachineOperand::jumpTable(*Index, TargetFlags);
+    advance();
+    break;
+  }
+  case MITokenKind::NamedGlobalValue:
+  case MITokenKind::GlobalValue: {
+    const std::string Name = symbolName(OperandToken);
+    advance();
+    std::int64_t Offset = 0;
+    if (parseOptionalOffset(Offset))
+      return true;
+    auto Created = MachineOperand::globalSymbol(Name, Offset, TargetFlags);
+    if (!Created)
+      return importError(OperandToken, Created.error());
+    Operand = std::move(*Created);
+    break;
+  }
+  case MITokenKind::ExternalSymbol: {
+    const std::string Name = symbolName(OperandToken);
+    advance();
+    std::int64_t Offset = 0;
+    if (parseOptionalOffset(Offset))
+      return true;
+    auto Created = MachineOperand::externalSymbol(Name, Offset, TargetFlags);
+    if (!Created)
+      return importError(OperandToken, Created.error());
+    Operand = std::move(*Created);
+    break;
+  }
+  case MITokenKind::MCSymbol: {
+    const std::string Name = symbolName(OperandToken);
+    advance();
+    std::int64_t Offset = 0;
+    if (parseOptionalOffset(Offset))
+      return true;
+    auto Created = MachineOperand::mcSymbol(Name, Offset, TargetFlags);
+    if (!Created)
+      return importError(OperandToken, Created.error());
+    Operand = std::move(*Created);
+    break;
+  }
+  case MITokenKind::SubRegisterIndex: {
+    const SubRegIndexDesc *Description = Target.registers().subRegIndex(OperandToken.stringValue());
+    if (Description == nullptr)
+      return fail("unknown subregister index '" + std::string(OperandToken.stringValue()) + "'");
+    Operand =
+        MachineOperand::immediate(static_cast<std::int64_t>(Description->ID.value()), TargetFlags);
+    advance();
+    break;
+  }
+  case MITokenKind::Identifier: {
+    if (const auto Mask = Target.mirText().registerMask(OperandToken.stringValue())) {
+      auto Created = MachineOperand::registerMask(Mask, TargetFlags);
+      if (!Created)
+        return importError(OperandToken, Created.error());
+      Operand = std::move(*Created);
+      advance();
+    } else if (OperandToken.stringValue() == "CustomRegMask") {
+      if (TargetFlags != 0)
+        return fail("custom register masks cannot have target flags");
+      return parseCustomMaskOperand(Result);
+    } else if (OperandToken.stringValue().starts_with('i')) {
+      if (parseTypedIntegerOperand(Result))
+        return true;
+      Result.Operand.setTargetFlags(TargetFlags);
+      return false;
+    } else {
+      return fail("unknown named machine operand '" + std::string(OperandToken.stringValue()) +
+                  "'");
+    }
+    break;
+  }
+  case MITokenKind::Keyword:
+    HasOperand = false;
+    break;
+  default:
+    return fail("expected a machine operand");
+  }
+
+  if (!HasOperand) {
+    bool Failed = false;
+    if (OperandToken.isKeyword("intpred"))
+      Failed = parsePredicateOperand(Result, false);
+    else if (OperandToken.isKeyword("floatpred"))
+      Failed = parsePredicateOperand(Result, true);
+    else if (OperandToken.isKeyword("shufflemask"))
+      Failed = parseShuffleMaskOperand(Result);
+    else if (OperandToken.isKeyword("dbg-instr-ref"))
+      Failed = parseDebugInstrRefOperand(Result);
+    else if (OperandToken.isKeyword("lanemask"))
+      Failed = parseLaneMaskOperand(Result);
+    else if (OperandToken.isKeyword("intrinsic"))
+      Failed = parseIntrinsicOperand(Result);
+    else if (OperandToken.isKeyword("target-index"))
+      Failed = parseTargetIndexOperand(Result);
+    else if (OperandToken.isKeyword("liveout"))
+      Failed = parseLiveOutMaskOperand(Result);
+    else if (OperandToken.isKeyword("blockaddress"))
+      Failed = parseBlockAddressOperand(Result);
+    else
+      return fail("unsupported machine operand spelling '" + std::string(OperandToken.spelling()) +
+                  "'");
+    if (!Failed)
+      Result.Operand.setTargetFlags(TargetFlags);
+    return Failed;
+  }
+
+  Result =
+      ParsedOperand{std::move(Operand), std::nullopt, {Begin.range().Begin, token().range().Begin}};
+  return false;
+}
+
+bool MIParser::Impl::parseInlineAsmExtraInfoOperand(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  InlineAsmExtraInfo ExtraInfo;
+  while (at(MITokenKind::Identifier)) {
+    const auto Bits = InlineAsmExtraInfo::namedFlagBits(token().stringValue());
+    if (!Bits) {
+      return fail("unknown inline asm extra info flag '" + std::string(token().stringValue()) +
+                  "'");
+    }
+    ExtraInfo = InlineAsmExtraInfo(ExtraInfo.rawValue() | *Bits);
+    advance();
+  }
+  Result = ParsedOperand{
+      MachineOperand::immediate(static_cast<std::int64_t>(ExtraInfo.rawValue())),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseInlineAsmOperandFlag(ParsedOperand &Result) {
+  const MIToken Begin = token();
+  const std::string KindName(token().stringValue());
+  const auto Kind = InlineAsmOperandFlag::kindForName(KindName);
+  if (!Kind)
+    return fail("unknown inline asm operand kind '" + KindName + "'");
+  advance();
+
+  InlineAsmOperandFlag Flag(*Kind);
+  if (at(MITokenKind::Identifier) && token().stringValue() == "tiedto") {
+    advance();
+    if (!consume(MITokenKind::Colon))
+      return fail("expected ':' after 'tiedto'");
+    if (!at(MITokenKind::NamedRegister))
+      return fail("expected '$N' operand number after 'tiedto:'");
+    std::uint64_t OperandNumber = 0;
+    if (!parseUnsignedDecimal(token().stringValue(), OperandNumber) ||
+        OperandNumber > std::numeric_limits<std::uint32_t>::max() ||
+        !Flag.setMatchingOperand(static_cast<std::uint32_t>(OperandNumber))) {
+      return fail("invalid operand number in tiedto constraint");
+    }
+    advance();
+  } else if (consume(MITokenKind::Colon)) {
+    if (!at(MITokenKind::Identifier))
+      return fail("expected register class or memory constraint name after ':'");
+    const std::string Constraint(token().stringValue());
+    if (*Kind == InlineAsmOperandKind::Memory) {
+      const auto MemoryConstraint = InlineAsmOperandFlag::memoryConstraintForName(Constraint);
+      if (!MemoryConstraint)
+        return fail("unknown memory constraint '" + Constraint + "'");
+      if (!Flag.setMemoryConstraint(*MemoryConstraint))
+        return fail("invalid memory constraint encoding");
+    } else if (*Kind == InlineAsmOperandKind::RegisterDef ||
+               *Kind == InlineAsmOperandKind::RegisterUse ||
+               *Kind == InlineAsmOperandKind::RegisterDefEarlyClobber) {
+      const RegisterClassDesc *RegisterClass = Target.registers().registerClass(Constraint);
+      if (RegisterClass == nullptr)
+        return fail("unknown register class '" + Constraint + "'");
+      if (!Flag.setRegisterClass(RegisterClass->ID.value()))
+        return fail("register class cannot be encoded in an inline asm operand flag");
+    }
+    advance();
+  }
+
+  Result = ParsedOperand{
+      MachineOperand::immediate(static_cast<std::int64_t>(Flag.rawValue())),
+      std::nullopt,
+      {Begin.range().Begin, token().range().Begin},
+  };
+  return false;
+}
+
+bool MIParser::Impl::parseBlockLiveIns(MachineBasicBlock &Block) {
+  advance();
+  if (expect(MITokenKind::Colon, "':' after liveins"))
+    return true;
+  if (token().isNewlineOrEnd())
+    return false;
+  do {
+    if (!at(MITokenKind::NamedRegister))
+      return fail("expected a physical register in liveins");
+    Register Reg;
+    if (parseRegister(Reg) || !Reg.isPhysical())
+      return true;
+    const auto Physical = Reg.physicalRegister();
+    if (!Physical)
+      return fail("expected a physical register in liveins");
+    LaneMask Lanes = LaneMask::all();
+    if (consume(MITokenKind::Colon)) {
+      std::uint64_t Raw = 0;
+      if (parseUnsigned(token(), Raw))
+        return fail("invalid live-in lane mask");
+      Lanes = LaneMask::fromRaw(Raw);
+      advance();
+    }
+    auto Added = Block.addLiveIn(*Physical, Lanes);
+    if (!Added)
+      return importError(token(), Added.error());
+  } while (consume(MITokenKind::Comma));
+  return false;
+}
+
+bool MIParser::Impl::parseBlockSuccessors(MachineBasicBlock &Block) {
+  advance();
+  if (expect(MITokenKind::Colon, "':' after successors"))
+    return true;
+  ExplicitSuccessorBlocks.insert(&Block);
+  if (token().isNewlineOrEnd())
+    return false;
+  do {
+    if (!at(MITokenKind::MachineBasicBlock))
+      return fail("expected a machine basic block reference");
+    MachineBasicBlock *Successor = blockFor(token());
+    if (Successor == nullptr)
+      return true;
+    advance();
+    BranchProbability Probability = BranchProbability::zero();
+    if (consume(MITokenKind::LeftParen)) {
+      std::uint32_t Weight = 0;
+      if (parseUnsigned32(token(), Weight))
+        return fail("expected unsigned integer");
+      Probability = BranchProbability::fromRaw(Weight);
+      advance();
+      if (expect(MITokenKind::RightParen, "')' after successor weight"))
+        return true;
+    }
+    auto Added = Function.cfgUpdater().addSuccessor(Block, *Successor, Probability);
+    if (!Added)
+      return importError(token(), Added.error());
+  } while (consume(MITokenKind::Comma));
+  return false;
+}
+
+bool MIParser::Impl::parseInstruction(MachineBasicBlock &Block, bool InBundle,
+                                      MachineInstr *PreviousInstruction, MachineInstr *&Result) {
+  if (ParsedInstructionCount >= Options.MaximumInstructions)
+    return fail("machine instruction count exceeds parser limit");
+
+  std::vector<ParsedOperand> Operands;
+  while (token().isRegister() || token().isRegisterFlag()) {
+    ParsedOperand Operand{MachineOperand::immediate(0), std::nullopt, {}};
+    if (parseRegisterOperand(true, Operand))
+      return true;
+    Operands.push_back(std::move(Operand));
+    if (!consume(MITokenKind::Comma))
+      break;
+  }
+  if (!Operands.empty() && expect(MITokenKind::Equal, "'=' after register definitions"))
+    return true;
+
+  MachineInstrFlags Flags;
+  while (isInstructionFlag(token())) {
+    const auto Flag = instructionFlag(token().stringValue());
+    if (!Flag)
+      return fail("unknown instruction flag");
+    if (Flags.has(*Flag))
+      return fail("duplicate instruction flag '" + std::string(token().stringValue()) + "'");
+    Flags.set(*Flag);
+    advance();
+  }
+  if (!at(MITokenKind::Identifier))
+    return fail("expected a machine instruction name");
+  const MIToken OpcodeToken = token();
+  const InstructionDescriptor *Descriptor =
+      Target.instructions().descriptor(OpcodeToken.stringValue());
+  if (Descriptor == nullptr)
+    return fail("unknown machine instruction '" + std::string(OpcodeToken.stringValue()) + "'");
+  advance();
+  const bool IsInlineAsm = Descriptor->Name == "INLINEASM" || Descriptor->Name == "INLINEASM_BR";
+
+  while (!token().isNewlineOrEnd() && !at(MITokenKind::DoubleColon) &&
+         !at(MITokenKind::LeftBrace) && !atKeyword("debug-instr-number") &&
+         !atKeyword("debug-location") && !atKeyword("pre-instr-symbol") &&
+         !atKeyword("post-instr-symbol") && !atKeyword("heap-alloc-marker") &&
+         !atKeyword("pcsections") && !atKeyword("mmra") && !atKeyword("cfi-type") &&
+         !atKeyword("deactivation-symbol")) {
+    if (Operands.size() >= Options.MaximumOperandsPerInstruction)
+      return fail("instruction operand count exceeds parser limit");
+    ParsedOperand Operand{MachineOperand::immediate(0), std::nullopt, {}};
+    const bool IsInlineAsmExtraInfo = IsInlineAsm &&
+                                      Operands.size() == InlineAsmExtraInfoOperandIndex &&
+                                      at(MITokenKind::Identifier);
+    const bool IsInlineAsmOperandFlag = IsInlineAsm &&
+                                        Operands.size() >= InlineAsmFirstConstraintOperandIndex &&
+                                        at(MITokenKind::Identifier);
+    if (IsInlineAsmExtraInfo ? parseInlineAsmExtraInfoOperand(Operand)
+                             : (IsInlineAsmOperandFlag ? parseInlineAsmOperandFlag(Operand)
+                                                       : parseOperand(false, Operand)))
+      return true;
+    Operands.push_back(std::move(Operand));
+    if (token().isNewlineOrEnd() || at(MITokenKind::DoubleColon) || at(MITokenKind::LeftBrace) ||
+        atKeyword("debug-instr-number") || atKeyword("debug-location"))
+      break;
+    if (expect(MITokenKind::Comma, "',' before the next machine operand"))
+      return true;
+  }
+
+  std::uint32_t DebugNumber = 0;
+  std::optional<MachineDebugLocation> DebugLocation;
+  std::optional<std::string> PreInstrSymbol;
+  std::optional<std::string> PostInstrSymbol;
+  std::optional<MachineMetadataReference> HeapAllocMarker;
+  std::optional<MachineMetadataReference> PCSections;
+  std::optional<MachineMetadataReference> MMRA;
+  std::optional<std::uint32_t> CFIType;
+  std::optional<std::string> DeactivationSymbol;
+  std::unordered_set<std::string> SeenAttachments;
+  while (atKeyword("debug-instr-number") || atKeyword("debug-location") ||
+         atKeyword("pre-instr-symbol") || atKeyword("post-instr-symbol") ||
+         atKeyword("heap-alloc-marker") || atKeyword("pcsections") || atKeyword("mmra") ||
+         atKeyword("cfi-type") || atKeyword("deactivation-symbol")) {
+    const std::string Name(token().stringValue());
+    if (!SeenAttachments.insert(Name).second)
+      return fail("duplicate instruction attachment '" + Name + "'");
+    advance();
+    if (Name == "debug-instr-number") {
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), DebugNumber) ||
+          DebugNumber == 0) {
+        return fail("invalid debug instruction number");
+      }
+      advance();
+    } else if (Name == "debug-location") {
+      if (at(MITokenKind::MetadataKeyword) && token().isMetadataKeyword("!DILocation")) {
+        std::vector<MachineDILocationFrame> InlineChain;
+        std::optional<MachineMetadataReference> TerminalInlinedAt;
+        if (parseInlineDILocation(InlineChain, TerminalInlinedAt))
+          return true;
+        auto Location = MachineDILocation::create(std::move(InlineChain), TerminalInlinedAt);
+        if (!Location)
+          return importError(OpcodeToken, Location.error());
+        DebugLocation = MachineDebugLocation::inlineLocation(std::move(*Location));
+      } else {
+        MachineMetadataReference Reference;
+        if (parseMetadataReference(Reference))
+          return true;
+        auto Created = MachineDebugLocation::reference(Reference);
+        if (!Created)
+          return importError(OpcodeToken, Created.error());
+        DebugLocation = std::move(*Created);
+      }
+    } else if (Name == "pre-instr-symbol" || Name == "post-instr-symbol") {
+      if (!at(MITokenKind::MCSymbol))
+        return fail("expected an MC symbol after '" + Name + "'");
+      if (Name == "pre-instr-symbol")
+        PreInstrSymbol = symbolName(token());
+      else
+        PostInstrSymbol = symbolName(token());
+      advance();
+    } else if (Name == "heap-alloc-marker" || Name == "pcsections" || Name == "mmra") {
+      MachineMetadataReference Reference;
+      if (parseMetadataReference(Reference))
+        return true;
+      if (Name == "heap-alloc-marker")
+        HeapAllocMarker = Reference;
+      else if (Name == "pcsections")
+        PCSections = Reference;
+      else
+        MMRA = Reference;
+    } else if (Name == "cfi-type") {
+      std::uint32_t Type = 0;
+      if (!at(MITokenKind::IntegerLiteral) || parseUnsigned32(token(), Type) || Type == 0)
+        return fail("invalid nonzero CFI type");
+      CFIType = Type;
+      advance();
+    } else {
+      if (!at(MITokenKind::GlobalValue) && !at(MITokenKind::NamedGlobalValue))
+        return fail("expected a global value after 'deactivation-symbol'");
+      DeactivationSymbol = symbolName(token());
+      advance();
+    }
+    static_cast<void>(consume(MITokenKind::Comma));
+  }
+  std::vector<const MachineMemOperand *> MemOperands;
+  if (consume(MITokenKind::DoubleColon)) {
+    while (!token().isNewlineOrEnd() && !at(MITokenKind::LeftBrace)) {
+      if (MemOperands.size() >= Options.MaximumMemoryOperandsPerInstruction)
+        return fail("machine memory operand count exceeds parser limit");
+      const MachineMemOperand *MemOperand = nullptr;
+      if (parseMemoryOperand(MemOperand, Descriptor->InstructionOpcode))
+        return true;
+      MemOperands.push_back(MemOperand);
+      if (token().isNewlineOrEnd() || at(MITokenKind::LeftBrace))
+        break;
+      if (expect(MITokenKind::Comma, "',' before the next machine memory operand"))
+        return true;
+    }
+  }
+
+  auto Created = Function.createInstruction(Descriptor->InstructionOpcode);
+  if (!Created)
+    return importError(OpcodeToken, Created.error());
+  MachineInstr *Instruction = *Created;
+  Instruction->setFlags(Flags);
+  for (ParsedOperand &Parsed : Operands) {
+    auto Added = Instruction->addOperand(std::move(Parsed.Operand));
+    if (!Added)
+      return importError(OpcodeToken, Added.error());
+  }
+  for (std::size_t Index = 0; Index < Operands.size(); ++Index) {
+    if (!Operands[Index].TiedDef)
+      continue;
+    if (*Operands[Index].TiedDef >= Operands.size())
+      return fail(OpcodeToken, "tied-def operand index is out of range");
+    auto Tied = Instruction->tieOperands(*Operands[Index].TiedDef, Index);
+    if (!Tied)
+      return importError(OpcodeToken, Tied.error());
+  }
+  for (const MachineMemOperand *MemOperand : MemOperands) {
+    auto Added = Instruction->addMemOperand(*MemOperand);
+    if (!Added)
+      return importError(OpcodeToken, Added.error());
+  }
+  if (DebugNumber != 0) {
+    auto SetNumber = Instruction->setDebugInstrNumber(DebugNumber);
+    if (!SetNumber)
+      return importError(OpcodeToken, SetNumber.error());
+  }
+  if (DebugLocation) {
+    auto SetLocation = Instruction->setDebugLocation(std::move(*DebugLocation));
+    if (!SetLocation)
+      return importError(OpcodeToken, SetLocation.error());
+  }
+  if (PreInstrSymbol) {
+    auto SetSymbol = Instruction->setPreInstrSymbol(std::move(*PreInstrSymbol));
+    if (!SetSymbol)
+      return importError(OpcodeToken, SetSymbol.error());
+  }
+  if (PostInstrSymbol) {
+    auto SetSymbol = Instruction->setPostInstrSymbol(std::move(*PostInstrSymbol));
+    if (!SetSymbol)
+      return importError(OpcodeToken, SetSymbol.error());
+  }
+  if (HeapAllocMarker) {
+    auto SetMarker = Instruction->setHeapAllocMarker(*HeapAllocMarker);
+    if (!SetMarker)
+      return importError(OpcodeToken, SetMarker.error());
+  }
+  if (PCSections) {
+    auto SetSections = Instruction->setPCSections(*PCSections);
+    if (!SetSections)
+      return importError(OpcodeToken, SetSections.error());
+  }
+  if (MMRA) {
+    auto SetMMRA = Instruction->setMMRA(*MMRA);
+    if (!SetMMRA)
+      return importError(OpcodeToken, SetMMRA.error());
+  }
+  if (CFIType) {
+    auto SetType = Instruction->setCFIType(*CFIType);
+    if (!SetType)
+      return importError(OpcodeToken, SetType.error());
+  }
+  if (DeactivationSymbol) {
+    auto SetSymbol = Instruction->setDeactivationSymbol(std::move(*DeactivationSymbol));
+    if (!SetSymbol)
+      return importError(OpcodeToken, SetSymbol.error());
+  }
+  if (InBundle) {
+    Flags.set(MachineInstrFlag::BundledWithPred);
+    Instruction->setFlags(Flags);
+    if (PreviousInstruction != nullptr) {
+      MachineInstrFlags PreviousFlags = PreviousInstruction->flags();
+      PreviousFlags.set(MachineInstrFlag::BundledWithSucc);
+      PreviousInstruction->setFlags(PreviousFlags);
+    }
+  }
+  auto Appended = Block.appendInstruction(*Instruction);
+  if (!Appended)
+    return importError(OpcodeToken, Appended.error());
+
+  ++ParsedInstructionCount;
+  Result = Instruction;
+  return false;
+}
+
+bool MIParser::Impl::parseSecondPass() {
+  Position = 0;
+  while (consume(MITokenKind::Newline)) {
+  }
+  while (!at(MITokenKind::EndOfFile)) {
+    if (!at(MITokenKind::MachineBasicBlockLabel))
+      return fail("expected a machine basic block definition");
+    std::uint32_t ID = 0;
+    if (parseBlockDefinition(false, ID))
+      return true;
+    MachineBasicBlock *Block = Blocks.at(ID);
+
+    while (consume(MITokenKind::Newline)) {
+    }
+    while (atKeyword("liveins") || atKeyword("successors")) {
+      if ((atKeyword("liveins") && parseBlockLiveIns(*Block)) ||
+          (atKeyword("successors") && parseBlockSuccessors(*Block))) {
+        return true;
+      }
+      if (!token().isNewlineOrEnd())
+        return fail("expected a line break after the block list");
+      while (consume(MITokenKind::Newline)) {
+      }
+    }
+
+    bool InBundle = false;
+    MachineInstr *PreviousInstruction = nullptr;
+    while (!at(MITokenKind::MachineBasicBlockLabel) && !at(MITokenKind::EndOfFile)) {
+      if (consume(MITokenKind::Newline))
+        continue;
+      if (consume(MITokenKind::RightBrace)) {
+        if (!InBundle)
+          return fail("closing brace without an active instruction bundle");
+        InBundle = false;
+        continue;
+      }
+
+      MachineInstr *Instruction = nullptr;
+      if (parseInstruction(*Block, InBundle, PreviousInstruction, Instruction))
+        return true;
+      PreviousInstruction = Instruction;
+      if (consume(MITokenKind::LeftBrace)) {
+        if (InBundle)
+          return fail("nested instruction bundles are not allowed");
+        MachineInstrFlags BundleFlags = Instruction->flags();
+        BundleFlags.set(MachineInstrFlag::BundledWithSucc);
+        Instruction->setFlags(BundleFlags);
+        InBundle = true;
+      }
+      if (!token().isNewlineOrEnd() && !at(MITokenKind::RightBrace))
+        return fail("expected a line break after the machine instruction");
+    }
+    if (InBundle)
+      return fail("unterminated instruction bundle");
+  }
+  return false;
+}
+
+bool MIParser::Impl::inferSuccessors() {
+  for (MachineBasicBlock *Block = Function.firstBlock(); Block != nullptr; Block = Block->next()) {
+    if (ExplicitSuccessorBlocks.contains(Block))
+      continue;
+
+    bool BlocksFallthrough = true;
+    std::vector<MachineBasicBlock *> Successors;
+    for (MachineInstr *Instruction = Block->firstInstruction(); Instruction != nullptr;
+         Instruction = Instruction->next()) {
+      const InstructionDescriptor *Descriptor =
+          Target.instructions().descriptor(Instruction->opcode());
+      if (Descriptor == nullptr)
+        return fail("instruction has no target descriptor while inferring successors");
+      if (Descriptor->Flags.has(InstructionFlag::Branch)) {
+        for (const MachineOperand &Operand : Instruction->operands()) {
+          if (const BasicBlockOperand *TargetBlock = Operand.getIf<BasicBlockOperand>()) {
+            if (std::ranges::find(Successors, TargetBlock->Block) == Successors.end())
+              Successors.push_back(TargetBlock->Block);
+          }
+        }
+      }
+      if (Descriptor->Flags.has(InstructionFlag::Barrier))
+        BlocksFallthrough = false;
+    }
+    if (BlocksFallthrough && Block->next() != nullptr &&
+        std::ranges::find(Successors, Block->next()) == Successors.end())
+      Successors.push_back(Block->next());
+    if (Successors.empty())
+      continue;
+    const auto Probability =
+        BranchProbability::fromFraction(1U, static_cast<std::uint32_t>(Successors.size()));
+    if (!Probability)
+      return importError(token(), Probability.error());
+    for (MachineBasicBlock *Successor : Successors) {
+      auto Added = Function.cfgUpdater().addSuccessor(*Block, *Successor, *Probability);
+      if (!Added)
+        return importError(token(), Added.error());
+    }
+  }
+  return false;
+}
+
+Expected<void> MIParser::Impl::parse() {
+  if (ParseAttempted)
+    return makeUnexpected(ErrorCode::InvalidArgument, "MI parser can only be run once");
+  ParseAttempted = true;
+  if (Function.blockCount() != 0 || !Function.allInstructions().empty()) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "MI parser requires a staging machine function with an empty body");
+  }
+  for (const MIVirtualRegisterSlot &Slot : Context.VirtualRegisters) {
+    if (!Slot.Reg.isVirtual() || !Function.registerInfo().isKnownVirtualRegister(Slot.Reg)) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "MI parser virtual-register slot maps to an unknown register");
+    }
+    if (!NumericVirtualRegisters.emplace(Slot.TextID, Slot.Reg).second) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "MI parser virtual-register text IDs must be unique");
+    }
+  }
+  if (tokenize())
+    return failureResult();
+  if (parseFirstPass() || parseSecondPass() || inferSuccessors())
+    return failureResult();
+
+  Function.renumberBlocks();
+  if (Options.VerifyAfterParse) {
+    auto Verified =
+        MachineVerifier::verify(Function, Target,
+                                MachineVerifierOptions{.Mode = MachineVerifierMode::Generic,
+                                                       .Stage = std::nullopt,
+                                                       .VerifyProperties = false});
+    if (!Verified) {
+      static_cast<void>(fail(token(), "parsed machine function failed verification: " +
+                                          std::string(Verified.error().message())));
+      return failureResult();
+    }
+  }
+  return {};
+}
+
+MIParser::MIParser(MachineFunction &Function, const TargetDescription &Target,
+                   std::string SourceName, std::string SourceText, MIParserContext Context,
+                   MIParserOptions Options)
+    : Implementation(std::make_unique<Impl>(Function, Target, std::move(SourceName),
+                                            std::move(SourceText), std::move(Context), Options)) {}
+
+MIParser::MIParser(MIParser &&) noexcept = default;
+
+MIParser &MIParser::operator=(MIParser &&) noexcept = default;
+
+MIParser::~MIParser() = default;
+
+Expected<void> MIParser::parse() {
+  return Implementation->parse();
+}
+
+const TextSource &MIParser::source() const noexcept {
+  return Implementation->source();
+}
+
+std::span<const TextDiagnostic> MIParser::diagnostics() const noexcept {
+  return Implementation->diagnostics();
+}
+
+bool MIParser::failed() const noexcept {
+  return Implementation->failed();
+}
+
+} // namespace rcc::mir