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//===- llvm/MC/MCTargetAsmParser.h - Target Assembly Parser -----*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCParser/MCAsmParserExtension.h"
#include "llvm/MC/MCParser/MCParsedAsmOperand.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/SMLoc.h"
#include <cstdint>
#include <memory>
namespace llvm {
class MCContext;
class MCInst;
class MCInstrInfo;
class MCRegister;
class MCStreamer;
class MCSubtargetInfo;
class MCSymbol;
template <typename T> class SmallVectorImpl;
using OperandVector = SmallVectorImpl<std::unique_ptr<MCParsedAsmOperand>>;
enum AsmRewriteKind {
AOK_Align, // Rewrite align as .align.
AOK_EVEN, // Rewrite even as .even.
AOK_Emit, // Rewrite _emit as .byte.
AOK_CallInput, // Rewrite in terms of ${N:P}.
AOK_Input, // Rewrite in terms of $N.
AOK_Output, // Rewrite in terms of $N.
AOK_SizeDirective, // Add a sizing directive (e.g., dword ptr).
AOK_Label, // Rewrite local labels.
AOK_EndOfStatement, // Add EndOfStatement (e.g., "\n\t").
AOK_Skip, // Skip emission (e.g., offset/type operators).
AOK_IntelExpr // SizeDirective SymDisp [BaseReg + IndexReg * Scale + ImmDisp]
const char AsmRewritePrecedence [] = {
2, // AOK_Align
2, // AOK_EVEN
2, // AOK_Emit
3, // AOK_Input
3, // AOK_CallInput
3, // AOK_Output
5, // AOK_SizeDirective
1, // AOK_Label
5, // AOK_EndOfStatement
2, // AOK_Skip
2 // AOK_IntelExpr
// Represent the various parts which make up an intel expression,
// used for emitting compound intel expressions
struct IntelExpr {
bool NeedBracs = false;
int64_t Imm = 0;
StringRef BaseReg;
StringRef IndexReg;
StringRef OffsetName;
unsigned Scale = 1;
IntelExpr() = default;
// [BaseReg + IndexReg * ScaleExpression + OFFSET name + ImmediateExpression]
IntelExpr(StringRef baseReg, StringRef indexReg, unsigned scale,
StringRef offsetName, int64_t imm, bool needBracs)
: NeedBracs(needBracs), Imm(imm), BaseReg(baseReg), IndexReg(indexReg),
OffsetName(offsetName), Scale(1) {
if (scale)
Scale = scale;
bool hasBaseReg() const { return !BaseReg.empty(); }
bool hasIndexReg() const { return !IndexReg.empty(); }
bool hasRegs() const { return hasBaseReg() || hasIndexReg(); }
bool hasOffset() const { return !OffsetName.empty(); }
// Normally we won't emit immediates unconditionally,
// unless we've got no other components
bool emitImm() const { return !(hasRegs() || hasOffset()); }
bool isValid() const {
return (Scale == 1) ||
(hasIndexReg() && (Scale == 2 || Scale == 4 || Scale == 8));
struct AsmRewrite {
AsmRewriteKind Kind;
SMLoc Loc;
unsigned Len;
bool Done;
int64_t Val;
StringRef Label;
IntelExpr IntelExp;
bool IntelExpRestricted;
AsmRewrite(AsmRewriteKind kind, SMLoc loc, unsigned len = 0, int64_t val = 0,
bool Restricted = false)
: Kind(kind), Loc(loc), Len(len), Done(false), Val(val) {
IntelExpRestricted = Restricted;
AsmRewrite(AsmRewriteKind kind, SMLoc loc, unsigned len, StringRef label)
: AsmRewrite(kind, loc, len) { Label = label; }
AsmRewrite(SMLoc loc, unsigned len, IntelExpr exp)
: AsmRewrite(AOK_IntelExpr, loc, len) { IntelExp = exp; }
struct ParseInstructionInfo {
SmallVectorImpl<AsmRewrite> *AsmRewrites = nullptr;
ParseInstructionInfo() = default;
ParseInstructionInfo(SmallVectorImpl<AsmRewrite> *rewrites)
: AsmRewrites(rewrites) {}
enum OperandMatchResultTy {
MatchOperand_Success, // operand matched successfully
MatchOperand_NoMatch, // operand did not match
MatchOperand_ParseFail // operand matched but had errors
enum class DiagnosticPredicateTy {
// When an operand is parsed, the assembler will try to iterate through a set of
// possible operand classes that the operand might match and call the
// corresponding PredicateMethod to determine that.
// If there are two AsmOperands that would give a specific diagnostic if there
// is no match, there is currently no mechanism to distinguish which operand is
// a closer match. The DiagnosticPredicate distinguishes between 'completely
// no match' and 'near match', so the assembler can decide whether to give a
// specific diagnostic, or use 'InvalidOperand' and continue to find a
// 'better matching' diagnostic.
// For example:
// opcode opnd0, onpd1, opnd2
// where:
// opnd2 could be an 'immediate of range [-8, 7]'
// opnd2 could be a 'register + shift/extend'.
// If opnd2 is a valid register, but with a wrong shift/extend suffix, it makes
// little sense to give a diagnostic that the operand should be an immediate
// in range [-8, 7].
// This is a light-weight alternative to the 'NearMissInfo' approach
// below which collects *all* possible diagnostics. This alternative
// is optional and fully backward compatible with existing
// PredicateMethods that return a 'bool' (match or no match).
struct DiagnosticPredicate {
DiagnosticPredicateTy Type;
explicit DiagnosticPredicate(bool Match)
: Type(Match ? DiagnosticPredicateTy::Match
: DiagnosticPredicateTy::NearMatch) {}
DiagnosticPredicate(DiagnosticPredicateTy T) : Type(T) {}
DiagnosticPredicate(const DiagnosticPredicate &) = default;
DiagnosticPredicate& operator=(const DiagnosticPredicate &) = default;
operator bool() const { return Type == DiagnosticPredicateTy::Match; }
bool isMatch() const { return Type == DiagnosticPredicateTy::Match; }
bool isNearMatch() const { return Type == DiagnosticPredicateTy::NearMatch; }
bool isNoMatch() const { return Type == DiagnosticPredicateTy::NoMatch; }
// When matching of an assembly instruction fails, there may be multiple
// encodings that are close to being a match. It's often ambiguous which one
// the programmer intended to use, so we want to report an error which mentions
// each of these "near-miss" encodings. This struct contains information about
// one such encoding, and why it did not match the parsed instruction.
class NearMissInfo {
enum NearMissKind {
// The encoding is valid for the parsed assembly string. This is only used
// internally to the table-generated assembly matcher.
static NearMissInfo getSuccess() { return NearMissInfo(); }
// The instruction encoding is not valid because it requires some target
// features that are not currently enabled. MissingFeatures has a bit set for
// each feature that the encoding needs but which is not enabled.
static NearMissInfo getMissedFeature(const FeatureBitset &MissingFeatures) {
NearMissInfo Result;
Result.Kind = NearMissFeature;
Result.Features = MissingFeatures;
return Result;
// The instruction encoding is not valid because the target-specific
// predicate function returned an error code. FailureCode is the
// target-specific error code returned by the predicate.
static NearMissInfo getMissedPredicate(unsigned FailureCode) {
NearMissInfo Result;
Result.Kind = NearMissPredicate;
Result.PredicateError = FailureCode;
return Result;
// The instruction encoding is not valid because one (and only one) parsed
// operand is not of the correct type. OperandError is the error code
// relating to the operand class expected by the encoding. OperandClass is
// the type of the expected operand. Opcode is the opcode of the encoding.
// OperandIndex is the index into the parsed operand list.
static NearMissInfo getMissedOperand(unsigned OperandError,
unsigned OperandClass, unsigned Opcode,
unsigned OperandIndex) {
NearMissInfo Result;
Result.Kind = NearMissOperand;
Result.MissedOperand.Error = OperandError;
Result.MissedOperand.Class = OperandClass;
Result.MissedOperand.Opcode = Opcode;
Result.MissedOperand.Index = OperandIndex;
return Result;
// The instruction encoding is not valid because it expects more operands
// than were parsed. OperandClass is the class of the expected operand that
// was not provided. Opcode is the instruction encoding.
static NearMissInfo getTooFewOperands(unsigned OperandClass,
unsigned Opcode) {
NearMissInfo Result;
Result.Kind = NearMissTooFewOperands;
Result.TooFewOperands.Class = OperandClass;
Result.TooFewOperands.Opcode = Opcode;
return Result;
operator bool() const { return Kind != NoNearMiss; }
NearMissKind getKind() const { return Kind; }
// Feature flags required by the instruction, that the current target does
// not have.
const FeatureBitset& getFeatures() const {
assert(Kind == NearMissFeature);
return Features;
// Error code returned by the target predicate when validating this
// instruction encoding.
unsigned getPredicateError() const {
assert(Kind == NearMissPredicate);
return PredicateError;
// MatchClassKind of the operand that we expected to see.
unsigned getOperandClass() const {
assert(Kind == NearMissOperand || Kind == NearMissTooFewOperands);
return MissedOperand.Class;
// Opcode of the encoding we were trying to match.
unsigned getOpcode() const {
assert(Kind == NearMissOperand || Kind == NearMissTooFewOperands);
return MissedOperand.Opcode;
// Error code returned when validating the operand.
unsigned getOperandError() const {
assert(Kind == NearMissOperand);
return MissedOperand.Error;
// Index of the actual operand we were trying to match in the list of parsed
// operands.
unsigned getOperandIndex() const {
assert(Kind == NearMissOperand);
return MissedOperand.Index;
NearMissKind Kind;
// These two structs share a common prefix, so we can safely rely on the fact
// that they overlap in the union.
struct MissedOpInfo {
unsigned Class;
unsigned Opcode;
unsigned Error;
unsigned Index;
struct TooFewOperandsInfo {
unsigned Class;
unsigned Opcode;
union {
FeatureBitset Features;
unsigned PredicateError;
MissedOpInfo MissedOperand;
TooFewOperandsInfo TooFewOperands;
NearMissInfo() : Kind(NoNearMiss) {}
/// MCTargetAsmParser - Generic interface to target specific assembly parsers.
class MCTargetAsmParser : public MCAsmParserExtension {
enum MatchResultTy {
protected: // Can only create subclasses.
MCTargetAsmParser(MCTargetOptions const &, const MCSubtargetInfo &STI,
const MCInstrInfo &MII);
/// Create a copy of STI and return a non-const reference to it.
MCSubtargetInfo &copySTI();
/// AvailableFeatures - The current set of available features.
FeatureBitset AvailableFeatures;
/// ParsingMSInlineAsm - Are we parsing ms-style inline assembly?
bool ParsingMSInlineAsm = false;
/// SemaCallback - The Sema callback implementation. Must be set when parsing
/// ms-style inline assembly.
MCAsmParserSemaCallback *SemaCallback = nullptr;
/// Set of options which affects instrumentation of inline assembly.
MCTargetOptions MCOptions;
/// Current STI.
const MCSubtargetInfo *STI;
const MCInstrInfo &MII;
MCTargetAsmParser(const MCTargetAsmParser &) = delete;
MCTargetAsmParser &operator=(const MCTargetAsmParser &) = delete;
~MCTargetAsmParser() override;
const MCSubtargetInfo &getSTI() const;
const FeatureBitset& getAvailableFeatures() const {
return AvailableFeatures;
void setAvailableFeatures(const FeatureBitset& Value) {
AvailableFeatures = Value;
bool isParsingMSInlineAsm () { return ParsingMSInlineAsm; }
void setParsingMSInlineAsm (bool Value) { ParsingMSInlineAsm = Value; }
MCTargetOptions getTargetOptions() const { return MCOptions; }
void setSemaCallback(MCAsmParserSemaCallback *Callback) {
SemaCallback = Callback;
// Target-specific parsing of expression.
virtual bool parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
return getParser().parsePrimaryExpr(Res, EndLoc, nullptr);
virtual bool parseRegister(MCRegister &Reg, SMLoc &StartLoc,
SMLoc &EndLoc) = 0;
/// tryParseRegister - parse one register if possible
/// Check whether a register specification can be parsed at the current
/// location, without failing the entire parse if it can't. Must not consume
/// tokens if the parse fails.
virtual OperandMatchResultTy
tryParseRegister(MCRegister &Reg, SMLoc &StartLoc, SMLoc &EndLoc) = 0;
/// ParseInstruction - Parse one assembly instruction.
/// The parser is positioned following the instruction name. The target
/// specific instruction parser should parse the entire instruction and
/// construct the appropriate MCInst, or emit an error. On success, the entire
/// line should be parsed up to and including the end-of-statement token. On
/// failure, the parser is not required to read to the end of the line.
/// \param Name - The instruction name.
/// \param NameLoc - The source location of the name.
/// \param Operands [out] - The list of parsed operands, this returns
/// ownership of them to the caller.
/// \return True on failure.
virtual bool ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
SMLoc NameLoc, OperandVector &Operands) = 0;
virtual bool ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
AsmToken Token, OperandVector &Operands) {
return ParseInstruction(Info, Name, Token.getLoc(), Operands);
/// ParseDirective - Parse a target specific assembler directive
/// The parser is positioned following the directive name. The target
/// specific directive parser should parse the entire directive doing or
/// recording any target specific work, or return true and do nothing if the
/// directive is not target specific. If the directive is specific for
/// the target, the entire line is parsed up to and including the
/// end-of-statement token and false is returned.
/// \param DirectiveID - the identifier token of the directive.
virtual bool ParseDirective(AsmToken DirectiveID) = 0;
/// MatchAndEmitInstruction - Recognize a series of operands of a parsed
/// instruction as an actual MCInst and emit it to the specified MCStreamer.
/// This returns false on success and returns true on failure to match.
/// On failure, the target parser is responsible for emitting a diagnostic
/// explaining the match failure.
virtual bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
OperandVector &Operands, MCStreamer &Out,
uint64_t &ErrorInfo,
bool MatchingInlineAsm) = 0;
/// Allows targets to let registers opt out of clobber lists.
virtual bool OmitRegisterFromClobberLists(unsigned RegNo) { return false; }
/// Allow a target to add special case operand matching for things that
/// tblgen doesn't/can't handle effectively. For example, literal
/// immediates on ARM. TableGen expects a token operand, but the parser
/// will recognize them as immediates.
virtual unsigned validateTargetOperandClass(MCParsedAsmOperand &Op,
unsigned Kind) {
return Match_InvalidOperand;
/// Validate the instruction match against any complex target predicates
/// before rendering any operands to it.
virtual unsigned
checkEarlyTargetMatchPredicate(MCInst &Inst, const OperandVector &Operands) {
return Match_Success;
/// checkTargetMatchPredicate - Validate the instruction match against
/// any complex target predicates not expressible via match classes.
virtual unsigned checkTargetMatchPredicate(MCInst &Inst) {
return Match_Success;
virtual void convertToMapAndConstraints(unsigned Kind,
const OperandVector &Operands) = 0;
/// Returns whether two operands are registers and are equal. This is used
/// by the tied-operands checks in the AsmMatcher. This method can be
/// overridden to allow e.g. a sub- or super-register as the tied operand.
virtual bool areEqualRegs(const MCParsedAsmOperand &Op1,
const MCParsedAsmOperand &Op2) const {
return Op1.isReg() && Op2.isReg() && Op1.getReg() == Op2.getReg();
// Return whether this parser uses assignment statements with equals tokens
virtual bool equalIsAsmAssignment() { return true; };
// Return whether this start of statement identifier is a label
virtual bool isLabel(AsmToken &Token) { return true; };
// Return whether this parser accept star as start of statement
virtual bool starIsStartOfStatement() { return false; };
virtual const MCExpr *applyModifierToExpr(const MCExpr *E,
MCContext &Ctx) {
return nullptr;
// For actions that have to be performed before a label is emitted
virtual void doBeforeLabelEmit(MCSymbol *Symbol, SMLoc IDLoc) {}
virtual void onLabelParsed(MCSymbol *Symbol) {}
/// Ensure that all previously parsed instructions have been emitted to the
/// output streamer, if the target does not emit them immediately.
virtual void flushPendingInstructions(MCStreamer &Out) {}
virtual const MCExpr *createTargetUnaryExpr(const MCExpr *E,
AsmToken::TokenKind OperatorToken,
MCContext &Ctx) {
return nullptr;
// For any initialization at the beginning of parsing.
virtual void onBeginOfFile() {}
// For any checks or cleanups at the end of parsing.
virtual void onEndOfFile() {}
} // end namespace llvm