lib/Sema/SemaStmtAsm.cpp

//===--- 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/MC/MCParser/MCParsedAsmOperand.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();
    else
      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<GCCAsmStmt::AsmStringPiece> AsmStrPieces) {
  for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
    const GCCAsmStmt::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::ActOnGCCAsmStmt(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 =
    reinterpret_cast<StringLiteral**>(constraints.data());
  Expr **Exprs = exprs.data();
  StringLiteral *AsmString = cast<StringLiteral>(asmString);
  StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(clobbers.data());

  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(),
                            diag::err_asm_invalid_output_constraint)
                       << Info.getConstraintStr());

    // Check that the output exprs are valid lvalues.
    Expr *OutputExpr = Exprs[i];
    if (CheckAsmLValue(OutputExpr, *this)) {
      return StmtError(Diag(OutputExpr->getLocStart(),
                  diag::err_asm_invalid_lvalue_in_output)
        << OutputExpr->getSourceRange());
    }

    OutputConstraintInfos.push_back(Info);
  }

  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(OutputConstraintInfos.data(),
                                                NumOutputs, Info)) {
      return StmtError(Diag(Literal->getLocStart(),
                            diag::err_asm_invalid_input_constraint)
                       << 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(),
                              diag::err_asm_invalid_lvalue_in_input)
                         << Info.getConstraintStr()
                         << InputExpr->getSourceRange());
    }

    if (Info.allowsRegister()) {
      if (InputExpr->getType()->isVoidType()) {
        return StmtError(Diag(InputExpr->getLocStart(),
                              diag::err_asm_invalid_type_in_input)
          << InputExpr->getType() << Info.getConstraintStr()
          << InputExpr->getSourceRange());
      }
    }

    ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
    if (Result.isInvalid())
      return StmtError();

    Exprs[i] = Result.take();
    InputConstraintInfos.push_back(Info);
  }

  // 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);
  }

  GCCAsmStmt *NS =
    new (Context) GCCAsmStmt(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<GCCAsmStmt::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())
      continue;

    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;
    else
      InputDomain = AD_Other;

    if (OutTy->isIntegerType() || OutTy->isPointerType())
      OutputDomain = AD_Int;
    else if (OutTy->isRealFloatingType())
      OutputDomain = AD_FP;
    else
      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)
      continue;

    // 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 &&
        OutputConstraintInfos[TiedTo].allowsRegister())
      continue;

    // 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);
      continue;
    }

    Diag(InputExpr->getLocStart(),
         diag::err_asm_tying_incompatible_types)
      << InTy << OutTy << OutputExpr->getSourceRange()
      << InputExpr->getSourceRange();
    return StmtError();
  }

  return Owned(NS);
}

// getSpelling - Get the spelling of the AsmTok token.
static StringRef getSpelling(Sema &SemaRef, Token AsmTok) {
  StringRef Asm;
  SmallString<512> TokenBuf;
  TokenBuf.resize(512);
  bool StringInvalid = false;
  Asm = SemaRef.PP.getSpelling(AsmTok, TokenBuf, &StringInvalid);
  assert (!StringInvalid && "Expected valid string!");
  return Asm;
}

// Build the inline assembly string.  Returns true on error.
static bool buildMSAsmString(Sema &SemaRef,
                             SourceLocation AsmLoc,
                             ArrayRef<Token> AsmToks,
                             std::string &AsmString) {
  assert (!AsmToks.empty() && "Didn't expect an empty AsmToks!");

  SmallString<512> Asm;
  for (unsigned i = 0, e = AsmToks.size(); i < e; ++i) {
    bool isNewAsm = ((i == 0) ||
                     AsmToks[i].isAtStartOfLine() ||
                     AsmToks[i].is(tok::kw_asm));
    if (isNewAsm) {
      if (i != 0)
        Asm += "\n\t";

      if (AsmToks[i].is(tok::kw_asm)) {
        i++; // Skip __asm
        if (i == e) {
          SemaRef.Diag(AsmLoc, diag::err_asm_empty);
          return true;
        }

      }
    }

    if (i && AsmToks[i].hasLeadingSpace() && !isNewAsm)
      Asm += ' ';

    StringRef Spelling = getSpelling(SemaRef, AsmToks[i]);
    Asm += Spelling;
  }
  AsmString = Asm.str();
  return false;
}

namespace {
enum AsmOpRewriteKind {
   AOK_Imm,
   AOK_Input,
   AOK_Output
};

struct AsmOpRewrite {
  AsmOpRewriteKind Kind;
  llvm::SMLoc Loc;
  unsigned Len;

public:
  AsmOpRewrite(AsmOpRewriteKind kind, llvm::SMLoc loc, unsigned len)
    : Kind(kind), Loc(loc), Len(len) { }
};

}

StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc, SourceLocation LBraceLoc,
                                ArrayRef<Token> AsmToks,SourceLocation EndLoc) {
  SmallVector<IdentifierInfo*, 4> Inputs;
  SmallVector<IdentifierInfo*, 4> Outputs;
  SmallVector<Expr*, 4> InputExprs;
  SmallVector<Expr*, 4> OutputExprs;
  SmallVector<StringRef, 4> Constraints;
  SmallVector<std::string, 4> InputConstraints;
  SmallVector<std::string, 4> OutputConstraints;

  SmallVector<StringRef, 4> Clobbers;
  std::set<std::string> ClobberRegs;

  SmallVector<struct AsmOpRewrite, 4> AsmStrRewrites;

  // Empty asm statements don't need to instantiate the AsmParser, etc.
  if (AsmToks.empty()) { 
    StringRef EmptyAsmStr;
    MSAsmStmt *NS =
      new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, /*IsSimple*/ true,
                              /*IsVolatile*/ true, AsmToks, Inputs, Outputs,
                              InputExprs, OutputExprs, EmptyAsmStr, Constraints,
                              Clobbers, EndLoc);
    return Owned(NS);
  }

  std::string AsmString;  
  if (buildMSAsmString(*this, AsmLoc, AsmToks, AsmString))
    return StmtError();

  // 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());
  OwningPtr<llvm::MCSubtargetInfo>
    STI(TheTarget->createMCSubtargetInfo(TT, "", ""));

  llvm::SourceMgr SrcMgr;
  llvm::MCContext Ctx(*MAI, *MRI, MOFI.get(), &SrcMgr);
  llvm::MemoryBuffer *Buffer =
    llvm::MemoryBuffer::getMemBuffer(AsmString, "<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));
  OwningPtr<llvm::MCAsmParser>
    Parser(createMCAsmParser(SrcMgr, Ctx, *Str.get(), *MAI));
  OwningPtr<llvm::MCTargetAsmParser>
    TargetParser(TheTarget->createMCAsmParser(*STI, *Parser));
    Parser->setParsingInlineAsm(true);

  // Get the instruction descriptor.
  const llvm::MCInstrInfo *MII = TheTarget->createMCInstrInfo(); 
  llvm::MCInstPrinter *IP =
    TheTarget->createMCInstPrinter(1, *MAI, *MII, *MRI, *STI);

  // Change to the Intel dialect.
  Parser->setAssemblerDialect(1);
  Parser->setTargetParser(*TargetParser.get());
  Parser->setParsingInlineAsm(true);

  // Prime the lexer.
  Parser->Lex();

  // While we have input, parse each statement.
  unsigned InputIdx = 0;
  unsigned OutputIdx = 0;
  while (Parser->getLexer().isNot(llvm::AsmToken::Eof)) {
    if (Parser->ParseStatement()) {
      // FIXME: The AsmParser should report errors, but we could potentially be
      // more verbose here.
      break;
    }

    if (Parser->isInstruction()) {
      const llvm::MCInstrDesc &Desc = MII->get(Parser->getOpcode());

      // Build the list of clobbers, outputs and inputs.
      for (unsigned i = 1, e = Parser->getNumParsedOperands(); i != e; ++i) {
        llvm::MCParsedAsmOperand &Operand = Parser->getParsedOperand(i);

        // Immediate.
        if (Operand.isImm()) {
          AsmStrRewrites.push_back(AsmOpRewrite(AOK_Imm,
                                                Operand.getStartLoc(),
                                                Operand.getNameLen()));
          continue;
        }


        // Register operand.
        if (Operand.isReg()) {
          unsigned NumDefs = Desc.getNumDefs();
          // Clobber.
          if (NumDefs && Operand.getMCOperandNum() < NumDefs) {
            std::string Reg;
            llvm::raw_string_ostream OS(Reg);
            IP->printRegName(OS, Operand.getReg());
            StringRef Clobber(OS.str());
            if (!Context.getTargetInfo().isValidClobber(Clobber))
              return StmtError(
                Diag(AsmLoc, diag::err_asm_unknown_register_name) << Clobber);
            ClobberRegs.insert(Reg);
          }
          continue;
        }


        // Expr/Input or Output.
        StringRef Name = Operand.getName();
        if (IdentifierInfo *II = &Context.Idents.get(Name)) {
          CXXScopeSpec SS;
          UnqualifiedId Id;
          SourceLocation Loc;
          Id.setIdentifier(II, AsmLoc);
          ExprResult Result = ActOnIdExpression(getCurScope(), SS, Loc, Id,
                                                false, false);
          if (!Result.isInvalid()) {
            bool isOutput = (i == 1) && Desc.mayStore();
            if (isOutput) {
              std::string Constraint = "=";
              ++InputIdx;
              Outputs.push_back(II);
              OutputExprs.push_back(Result.take());
              Constraint += Operand.getConstraint().str();
              OutputConstraints.push_back(Constraint);
              AsmStrRewrites.push_back(AsmOpRewrite(AOK_Output,
                                                    Operand.getStartLoc(),
                                                    Operand.getNameLen()));
            } else {
              Inputs.push_back(II);
              InputExprs.push_back(Result.take());
              InputConstraints.push_back(Operand.getConstraint().str());
              AsmStrRewrites.push_back(AsmOpRewrite(AOK_Input,
                                                    Operand.getStartLoc(),
                                                    Operand.getNameLen()));
            }
          }
        }
      }
      Parser->freeParsedOperands();
    }
  }
  for (std::set<std::string>::iterator I = ClobberRegs.begin(),
         E = ClobberRegs.end(); I != E; ++I)
    Clobbers.push_back(*I);

  // Merge the output and input constraints.  Output constraints are expected
  // first.
  for (SmallVectorImpl<std::string>::iterator I = OutputConstraints.begin(),
         E = OutputConstraints.end(); I != E; ++I)
    Constraints.push_back(*I);

  for (SmallVectorImpl<std::string>::iterator I = InputConstraints.begin(),
         E = InputConstraints.end(); I != E; ++I)
    Constraints.push_back(*I);

  // Build the IR assembly string.
  std::string AsmStringIR;
  llvm::raw_string_ostream OS(AsmStringIR);
  const char *Start = AsmString.c_str();
  for (SmallVectorImpl<struct AsmOpRewrite>::iterator I = AsmStrRewrites.begin(),
         E = AsmStrRewrites.end(); I != E; ++I) {
    const char *Loc = (*I).Loc.getPointer();

    // Emit everything up to the immediate/expression.
    OS << StringRef(Start, Loc - Start);

    // Rewrite expressions in $N notation.
    switch ((*I).Kind) {
    case AOK_Imm:
      OS << Twine("$$") + StringRef(Loc, (*I).Len);
      break;
    case AOK_Input:
      OS << '$';
      OS << InputIdx++;
      break;
    case AOK_Output:
      OS << '$';
      OS << OutputIdx++;
      break;
    }

    // Skip the original expression.
    Start = Loc + (*I).Len;
  }
  // Emit the remainder of the asm string.
  const char *AsmEnd = AsmString.c_str() + AsmString.size();
  if (Start != AsmEnd)
    OS << StringRef(Start, AsmEnd - Start);

  AsmString = OS.str();
  MSAsmStmt *NS =
    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, /*IsSimple*/ false,
                            /*IsVolatile*/ true, AsmToks, Inputs, Outputs,
                            InputExprs, OutputExprs, AsmString, Constraints,
                            Clobbers, EndLoc);
  return Owned(NS);
}