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//===--- SemaStmtAsm.cpp - Semantic Analysis for Asm Statements -----------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file implements semantic analysis for inline asm statements.
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCTargetAsmParser.h"
#include "llvm/MC/MCParser/MCAsmLexer.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
using namespace clang;
using namespace sema;
/// CheckAsmLValue - GNU C has an extremely ugly extension whereby they silently
/// ignore "noop" casts in places where an lvalue is required by an inline asm.
/// We emulate this behavior when -fheinous-gnu-extensions is specified, but
/// provide a strong guidance to not use it.
/// This method checks to see if the argument is an acceptable l-value and
/// returns false if it is a case we can handle.
static bool CheckAsmLValue(const Expr *E, Sema &S) {
// Type dependent expressions will be checked during instantiation.
if (E->isTypeDependent())
return false;
if (E->isLValue())
return false; // Cool, this is an lvalue.
// Okay, this is not an lvalue, but perhaps it is the result of a cast that we
// are supposed to allow.
const Expr *E2 = E->IgnoreParenNoopCasts(S.Context);
if (E != E2 && E2->isLValue()) {
if (!S.getLangOpts().HeinousExtensions)
S.Diag(E2->getLocStart(), diag::err_invalid_asm_cast_lvalue)
<< E->getSourceRange();
S.Diag(E2->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
<< E->getSourceRange();
// Accept, even if we emitted an error diagnostic.
return false;
// None of the above, just randomly invalid non-lvalue.
return true;
/// isOperandMentioned - Return true if the specified operand # is mentioned
/// anywhere in the decomposed asm string.
static bool isOperandMentioned(unsigned OpNo,
ArrayRef<AsmStmt::AsmStringPiece> AsmStrPieces) {
for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
const AsmStmt::AsmStringPiece &Piece = AsmStrPieces[p];
if (!Piece.isOperand()) continue;
// If this is a reference to the input and if the input was the smaller
// one, then we have to reject this asm.
if (Piece.getOperandNo() == OpNo)
return true;
return false;
StmtResult Sema::ActOnAsmStmt(SourceLocation AsmLoc, bool IsSimple,
bool IsVolatile, unsigned NumOutputs,
unsigned NumInputs, IdentifierInfo **Names,
MultiExprArg constraints, MultiExprArg exprs,
Expr *asmString, MultiExprArg clobbers,
SourceLocation RParenLoc) {
unsigned NumClobbers = clobbers.size();
StringLiteral **Constraints =
Expr **Exprs =;
StringLiteral *AsmString = cast<StringLiteral>(asmString);
StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(;
SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
// The parser verifies that there is a string literal here.
if (!AsmString->isAscii())
return StmtError(Diag(AsmString->getLocStart(),diag::err_asm_wide_character)
<< AsmString->getSourceRange());
for (unsigned i = 0; i != NumOutputs; i++) {
StringLiteral *Literal = Constraints[i];
if (!Literal->isAscii())
return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
<< Literal->getSourceRange());
StringRef OutputName;
if (Names[i])
OutputName = Names[i]->getName();
TargetInfo::ConstraintInfo Info(Literal->getString(), OutputName);
if (!Context.getTargetInfo().validateOutputConstraint(Info))
return StmtError(Diag(Literal->getLocStart(),
<< Info.getConstraintStr());
// Check that the output exprs are valid lvalues.
Expr *OutputExpr = Exprs[i];
if (CheckAsmLValue(OutputExpr, *this)) {
return StmtError(Diag(OutputExpr->getLocStart(),
<< OutputExpr->getSourceRange());
SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
StringLiteral *Literal = Constraints[i];
if (!Literal->isAscii())
return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
<< Literal->getSourceRange());
StringRef InputName;
if (Names[i])
InputName = Names[i]->getName();
TargetInfo::ConstraintInfo Info(Literal->getString(), InputName);
if (!Context.getTargetInfo().validateInputConstraint(,
NumOutputs, Info)) {
return StmtError(Diag(Literal->getLocStart(),
<< Info.getConstraintStr());
Expr *InputExpr = Exprs[i];
// Only allow void types for memory constraints.
if (Info.allowsMemory() && !Info.allowsRegister()) {
if (CheckAsmLValue(InputExpr, *this))
return StmtError(Diag(InputExpr->getLocStart(),
<< Info.getConstraintStr()
<< InputExpr->getSourceRange());
if (Info.allowsRegister()) {
if (InputExpr->getType()->isVoidType()) {
return StmtError(Diag(InputExpr->getLocStart(),
<< InputExpr->getType() << Info.getConstraintStr()
<< InputExpr->getSourceRange());
ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
if (Result.isInvalid())
return StmtError();
Exprs[i] = Result.take();
// Check that the clobbers are valid.
for (unsigned i = 0; i != NumClobbers; i++) {
StringLiteral *Literal = Clobbers[i];
if (!Literal->isAscii())
return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
<< Literal->getSourceRange());
StringRef Clobber = Literal->getString();
if (!Context.getTargetInfo().isValidClobber(Clobber))
return StmtError(Diag(Literal->getLocStart(),
diag::err_asm_unknown_register_name) << Clobber);
AsmStmt *NS =
new (Context) AsmStmt(Context, AsmLoc, IsSimple, IsVolatile, NumOutputs,
NumInputs, Names, Constraints, Exprs, AsmString,
NumClobbers, Clobbers, RParenLoc);
// Validate the asm string, ensuring it makes sense given the operands we
// have.
SmallVector<AsmStmt::AsmStringPiece, 8> Pieces;
unsigned DiagOffs;
if (unsigned DiagID = NS->AnalyzeAsmString(Pieces, Context, DiagOffs)) {
Diag(getLocationOfStringLiteralByte(AsmString, DiagOffs), DiagID)
<< AsmString->getSourceRange();
return StmtError();
// Validate tied input operands for type mismatches.
for (unsigned i = 0, e = InputConstraintInfos.size(); i != e; ++i) {
TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
// If this is a tied constraint, verify that the output and input have
// either exactly the same type, or that they are int/ptr operands with the
// same size (int/long, int*/long, are ok etc).
if (!Info.hasTiedOperand()) continue;
unsigned TiedTo = Info.getTiedOperand();
unsigned InputOpNo = i+NumOutputs;
Expr *OutputExpr = Exprs[TiedTo];
Expr *InputExpr = Exprs[InputOpNo];
if (OutputExpr->isTypeDependent() || InputExpr->isTypeDependent())
QualType InTy = InputExpr->getType();
QualType OutTy = OutputExpr->getType();
if (Context.hasSameType(InTy, OutTy))
continue; // All types can be tied to themselves.
// Decide if the input and output are in the same domain (integer/ptr or
// floating point.
enum AsmDomain {
AD_Int, AD_FP, AD_Other
} InputDomain, OutputDomain;
if (InTy->isIntegerType() || InTy->isPointerType())
InputDomain = AD_Int;
else if (InTy->isRealFloatingType())
InputDomain = AD_FP;
InputDomain = AD_Other;
if (OutTy->isIntegerType() || OutTy->isPointerType())
OutputDomain = AD_Int;
else if (OutTy->isRealFloatingType())
OutputDomain = AD_FP;
OutputDomain = AD_Other;
// They are ok if they are the same size and in the same domain. This
// allows tying things like:
// void* to int*
// void* to int if they are the same size.
// double to long double if they are the same size.
uint64_t OutSize = Context.getTypeSize(OutTy);
uint64_t InSize = Context.getTypeSize(InTy);
if (OutSize == InSize && InputDomain == OutputDomain &&
InputDomain != AD_Other)
// If the smaller input/output operand is not mentioned in the asm string,
// then we can promote the smaller one to a larger input and the asm string
// won't notice.
bool SmallerValueMentioned = false;
// If this is a reference to the input and if the input was the smaller
// one, then we have to reject this asm.
if (isOperandMentioned(InputOpNo, Pieces)) {
// This is a use in the asm string of the smaller operand. Since we
// codegen this by promoting to a wider value, the asm will get printed
// "wrong".
SmallerValueMentioned |= InSize < OutSize;
if (isOperandMentioned(TiedTo, Pieces)) {
// If this is a reference to the output, and if the output is the larger
// value, then it's ok because we'll promote the input to the larger type.
SmallerValueMentioned |= OutSize < InSize;
// If the smaller value wasn't mentioned in the asm string, and if the
// output was a register, just extend the shorter one to the size of the
// larger one.
if (!SmallerValueMentioned && InputDomain != AD_Other &&
// Either both of the operands were mentioned or the smaller one was
// mentioned. One more special case that we'll allow: if the tied input is
// integer, unmentioned, and is a constant, then we'll allow truncating it
// down to the size of the destination.
if (InputDomain == AD_Int && OutputDomain == AD_Int &&
!isOperandMentioned(InputOpNo, Pieces) &&
InputExpr->isEvaluatable(Context)) {
CastKind castKind =
(OutTy->isBooleanType() ? CK_IntegralToBoolean : CK_IntegralCast);
InputExpr = ImpCastExprToType(InputExpr, OutTy, castKind).take();
Exprs[InputOpNo] = InputExpr;
NS->setInputExpr(i, InputExpr);
<< InTy << OutTy << OutputExpr->getSourceRange()
<< InputExpr->getSourceRange();
return StmtError();
return Owned(NS);
// isMSAsmKeyword - Return true if this is an MS-style inline asm keyword. These
// require special handling.
static bool isMSAsmKeyword(StringRef Name) {
bool Ret = llvm::StringSwitch<bool>(Name)
.Cases("EVEN", "ALIGN", true) // Alignment directives.
.Cases("LENGTH", "SIZE", "TYPE", true) // Type and variable sizes.
.Case("_emit", true) // _emit Pseudoinstruction.
return Ret;
// getIdentifierInfo - Given a Name and a range of tokens, find the associated
// IdentifierInfo*.
static IdentifierInfo *getIdentifierInfo(StringRef Name,
ArrayRef<Token> AsmToks,
unsigned Begin, unsigned End) {
for (unsigned i = Begin; i <= End; ++i) {
IdentifierInfo *II = AsmToks[i].getIdentifierInfo();
if (II && II->getName() == Name)
return II;
return 0;
// getSpelling - Get the spelling of the AsmTok token.
static StringRef getSpelling(Sema &SemaRef, Token AsmTok) {
StringRef Asm;
SmallString<512> TokenBuf;
bool StringInvalid = false;
Asm = SemaRef.PP.getSpelling(AsmTok, TokenBuf, &StringInvalid);
assert (!StringInvalid && "Expected valid string!");
return Asm;
// Determine if we should bail on this MSAsm instruction.
static bool bailOnMSAsm(std::vector<StringRef> Piece) {
for (unsigned i = 0, e = Piece.size(); i != e; ++i)
if (isMSAsmKeyword(Piece[i]))
return true;
return false;
// Determine if we should bail on this MSAsm block.
static bool bailOnMSAsm(std::vector<std::vector<StringRef> > Pieces) {
for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
if (bailOnMSAsm(Pieces[i]))
return true;
return false;
// Determine if this is a simple MSAsm instruction.
static bool isSimpleMSAsm(std::vector<StringRef> &Pieces,
const TargetInfo &TI) {
if (isMSAsmKeyword(Pieces[0]))
return false;
for (unsigned i = 1, e = Pieces.size(); i != e; ++i)
if (!TI.isValidGCCRegisterName(Pieces[i]))
return false;
return true;
// Determine if this is a simple MSAsm block.
static bool isSimpleMSAsm(std::vector<std::vector<StringRef> > Pieces,
const TargetInfo &TI) {
for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
if (!isSimpleMSAsm(Pieces[i], TI))
return false;
return true;
// Break the AsmSting into pieces (i.e., mnemonic and operands).
static void buildMSAsmPieces(StringRef Asm, std::vector<StringRef> &Pieces) {
std::pair<StringRef,StringRef> Split = Asm.split(' ');
// Mnemonic
Asm = Split.second;
// Operands
while (!Asm.empty()) {
Split = Asm.split(", ");
Asm = Split.second;
static void buildMSAsmPieces(std::vector<std::string> &AsmStrings,
std::vector<std::vector<StringRef> > &Pieces) {
for (unsigned i = 0, e = AsmStrings.size(); i != e; ++i)
buildMSAsmPieces(AsmStrings[i], Pieces[i]);
// Build the unmodified AsmString used by the IR. Also build the individual
// asm instruction(s) and place them in the AsmStrings vector; these are fed
// to the AsmParser.
static std::string buildMSAsmString(Sema &SemaRef, ArrayRef<Token> AsmToks,
std::vector<std::string> &AsmStrings,
std::vector<std::pair<unsigned,unsigned> > &AsmTokRanges) {
assert (!AsmToks.empty() && "Didn't expect an empty AsmToks!");
SmallString<512> Res;
SmallString<512> Asm;
unsigned startTok = 0;
for (unsigned i = 0, e = AsmToks.size(); i < e; ++i) {
bool isNewAsm = i == 0 || AsmToks[i].isAtStartOfLine() ||
if (isNewAsm) {
if (i) {
AsmTokRanges.push_back(std::make_pair(startTok, i-1));
startTok = i;
Res += Asm;
Res += '\n';
if (AsmToks[i].is(tok::kw_asm)) {
i++; // Skip __asm
assert (i != e && "Expected another token");
if (i && AsmToks[i].hasLeadingSpace() && !isNewAsm)
Asm += ' ';
Asm += getSpelling(SemaRef, AsmToks[i]);
AsmTokRanges.push_back(std::make_pair(startTok, AsmToks.size()-1));
Res += Asm;
return Res.c_str();
MSAsmStmt *NS = \
new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, /*IsSimple*/ true, \
/*IsVolatile*/ true, AsmToks, Inputs, Outputs, \
InputExprs, OutputExprs, AsmString, Clobbers, \
StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc,
SourceLocation LBraceLoc,
ArrayRef<Token> AsmToks,
SourceLocation EndLoc) {
// MS-style inline assembly is not fully supported, so emit a warning.
Diag(AsmLoc, diag::warn_unsupported_msasm);
SmallVector<StringRef,4> Clobbers;
std::set<std::string> ClobberRegs;
SmallVector<IdentifierInfo*, 4> Inputs;
SmallVector<IdentifierInfo*, 4> Outputs;
SmallVector<Expr*, 4> InputExprs;
SmallVector<Expr*, 4> OutputExprs;
// Empty asm statements don't need to instantiate the AsmParser, etc.
if (AsmToks.empty()) {
StringRef AsmString;
return Owned(NS);
std::vector<std::string> AsmStrings;
std::vector<std::pair<unsigned,unsigned> > AsmTokRanges;
std::string AsmString = buildMSAsmString(*this, AsmToks, AsmStrings,
std::vector<std::vector<StringRef> > Pieces(AsmStrings.size());
buildMSAsmPieces(AsmStrings, Pieces);
bool IsSimple = isSimpleMSAsm(Pieces, Context.getTargetInfo());
// AsmParser doesn't fully support these asm statements.
if (bailOnMSAsm(Pieces)) { DEF_SIMPLE_MSASM; return Owned(NS); }
// Initialize targets and assembly printers/parsers.
// Get the target specific parser.
std::string Error;
const std::string &TT = Context.getTargetInfo().getTriple().getTriple();
const llvm::Target *TheTarget(llvm::TargetRegistry::lookupTarget(TT, Error));
OwningPtr<llvm::MCAsmInfo> MAI(TheTarget->createMCAsmInfo(TT));
OwningPtr<llvm::MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TT));
OwningPtr<llvm::MCObjectFileInfo> MOFI(new llvm::MCObjectFileInfo());
STI(TheTarget->createMCSubtargetInfo(TT, "", ""));
for (unsigned StrIdx = 0, e = AsmStrings.size(); StrIdx != e; ++StrIdx) {
llvm::SourceMgr SrcMgr;
llvm::MCContext Ctx(*MAI, *MRI, MOFI.get(), &SrcMgr);
llvm::MemoryBuffer *Buffer =
llvm::MemoryBuffer::getMemBuffer(AsmStrings[StrIdx], "<inline asm>");
// Tell SrcMgr about this buffer, which is what the parser will pick up.
SrcMgr.AddNewSourceBuffer(Buffer, llvm::SMLoc());
OwningPtr<llvm::MCStreamer> Str(createNullStreamer(Ctx));
Parser(createMCAsmParser(SrcMgr, Ctx, *Str.get(), *MAI));
TargetParser(TheTarget->createMCAsmParser(*STI, *Parser));
// Change to the Intel dialect.
// Prime the lexer.
// Parse the opcode.
StringRef IDVal;
// Canonicalize the opcode to lower case.
SmallString<128> Opcode;
for (unsigned j = 0, e = IDVal.size(); j != e; ++j)
// Parse the operands.
llvm::SMLoc IDLoc;
SmallVector<llvm::MCParsedAsmOperand*, 8> Operands;
bool HadError = TargetParser->ParseInstruction(Opcode.str(), IDLoc,
// If we had an error parsing the operands, fail gracefully.
if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
// Match the MCInstr.
unsigned ErrorInfo;
SmallVector<llvm::MCInst, 2> Instrs;
HadError = TargetParser->MatchInstruction(IDLoc, Operands, Instrs,
/*matchingInlineAsm*/ true);
// If we had an error parsing the operands, fail gracefully.
if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
// Get the instruction descriptor.
llvm::MCInst Inst = Instrs[0];
const llvm::MCInstrInfo *MII = TheTarget->createMCInstrInfo();
const llvm::MCInstrDesc &Desc = MII->get(Inst.getOpcode());
llvm::MCInstPrinter *IP =
TheTarget->createMCInstPrinter(1, *MAI, *MII, *MRI, *STI);
// Build the list of clobbers, outputs and inputs.
unsigned NumDefs = Desc.getNumDefs();
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i) {
const llvm::MCOperand &Op = Inst.getOperand(i);
// Immediate.
if (Op.isImm() || Op.isFPImm())
bool isDef = NumDefs && (i < NumDefs);
// Register/Clobber.
if (Op.isReg() && isDef) {
std::string Reg;
llvm::raw_string_ostream OS(Reg);
IP->printRegName(OS, Op.getReg());
StringRef Clobber(OS.str());
if (!Context.getTargetInfo().isValidClobber(Clobber))
return StmtError(Diag(AsmLoc, diag::err_asm_unknown_register_name) <<
// Expr/Input or Output.
if (Op.isExpr()) {
const llvm::MCExpr *Expr = Op.getExpr();
const llvm::MCSymbolRefExpr *SymRef;
if ((SymRef = dyn_cast<llvm::MCSymbolRefExpr>(Expr))) {
StringRef Name = SymRef->getSymbol().getName();
IdentifierInfo *II = getIdentifierInfo(Name, AsmToks,
if (II) {
CXXScopeSpec SS;
UnqualifiedId Id;
SourceLocation Loc;
Id.setIdentifier(II, AsmLoc);
ExprResult Result = ActOnIdExpression(getCurScope(), SS, Loc, Id,
false, false);
if (!Result.isInvalid()) {
if (isDef) {
} else {
for (std::set<std::string>::iterator I = ClobberRegs.begin(),
E = ClobberRegs.end(); I != E; ++I)
MSAsmStmt *NS =
new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, IsSimple,
/*IsVolatile*/ true, AsmToks, Inputs, Outputs,
InputExprs, OutputExprs, AsmString, Clobbers,
return Owned(NS);