[PATCH] Support constant expressions, including non-type template parameters, in pragma loop hints

Aaron Ballman aaron at aaronballman.com
Wed Jul 30 07:34:40 PDT 2014


On Tue, Jul 29, 2014 at 6:15 PM, Tyler Nowicki <tnowicki at apple.com> wrote:
> Hi Aaron,
>
> I’ve cut another piece off the constant expression patch. This piece adds
> the state variable to the loop hint attribute. Would you be able tor review
> it?
>
> Parts of this patch may seem a little overkill, they are necessary to
> support constant expressions. Specifically, the way the argument to a loop
> hint pragma is handled. The single token argument is replaced by an array of
> tokens which either give a keyword (single token) or a constant expression
> (multiple tokens). We need to have these cases separated out to pass the
> hint to the SemaStmtAttr handler. Consequently validation of the keywords
> must move from SemaStmtAttr handler to the loop hint annotation token
> handler. It makes the token handler a bit more complicated and the
> SemaStmtAttr a bit simpler.
>
> A couple of new tests are included as well.

I don't see any new tests in the patch file, did those get
accidentally left out?

Comments on the patch below.

> Index: include/clang/Basic/Attr.td
> ===================================================================
> --- include/clang/Basic/Attr.td (revision 214227)
> +++ include/clang/Basic/Attr.td (working copy)
> @@ -1784,13 +1784,19 @@
>  }
>
>  def LoopHint : Attr {
> -  /// vectorize: vectorizes loop operations if 'value != 0'.
> -  /// vectorize_width: vectorize loop operations with width 'value'.
> -  /// interleave: interleave multiple loop iterations if 'value != 0'.
> -  /// interleave_count: interleaves 'value' loop interations.
> -  /// unroll: fully unroll loop if 'value != 0'.
> -  /// unroll_count: unrolls loop 'value' times.
> +  /// #pragma clang loop <option> directive
> +  /// vectorize: vectorizes loop operations if State == Enable.
> +  /// vectorize_width: vectorize loop operations with width 'Value'.
> +  /// interleave: interleave multiple loop iterations if State == Enable.
> +  /// interleave_count: interleaves 'Value' loop interations.
> +  /// unroll: fully unroll loop if State == Enable.
> +  /// unroll_count: unrolls loop 'Value' times.
>
> +  /// #pragma unroll <argument> directive
> +  /// <no arg>: fully unrolls loop.
> +  /// boolean: fully unrolls loop if State == Enable.
> +  /// expression: unrolls loop 'Value' times.
> +
>    let Spellings = [Pragma<"clang", "loop">, Pragma<"", "unroll">,
>                     Pragma<"", "nounroll">];
>
> @@ -1800,6 +1806,9 @@
>                             "unroll", "unroll_count"],
>                            ["Vectorize", "VectorizeWidth", "Interleave", "InterleaveCount",
>                             "Unroll", "UnrollCount"]>,
> +              EnumArgument<"State", "StateType",

The name StateType isn't particularly descriptive. How about LoopHintState?

> +                           ["default", "enable", "disable"],
> +                           ["Default", "Enable", "Disable"]>,

This isn't really a "default" so much as "it's not Enabled or
Disabled", correct? Perhaps UsesValue instead? I know that's not quite
accurate either since it'll be used for #pragma unroll with no
arguments...

>                DefaultIntArgument<"Value", 1>];
>
>    let AdditionalMembers = [{
> @@ -1841,9 +1850,9 @@
>      if (option == VectorizeWidth || option == InterleaveCount ||
>          option == UnrollCount)
>        OS << value;
> -    else if (value < 0)
> +    else if (state == Default)
>        return "";
> -    else if (value > 0)
> +    else if (state == Enable)
>        OS << (option == Unroll ? "full" : "enable");
>      else
>        OS << "disable";
> Index: include/clang/Basic/DiagnosticParseKinds.td
> ===================================================================
> --- include/clang/Basic/DiagnosticParseKinds.td (revision 214227)
> +++ include/clang/Basic/DiagnosticParseKinds.td (working copy)
> @@ -917,10 +917,16 @@
>  def err_omp_expected_identifier_for_critical : Error<
>    "expected identifier specifying the name of the 'omp critical' directive">;
>
> +// Pragma support.
> +def err_pragma_invalid_keyword : Error<
> +  "%select{invalid|missing}0 argument; expected '%select{enable|full}1' or 'disable'">;
> +
>  // Pragma loop support.
>  def err_pragma_loop_invalid_option : Error<
>    "%select{invalid|missing}0 option%select{ %1|}0; expected vectorize, "
>    "vectorize_width, interleave, interleave_count, unroll, or unroll_count">;
> +def err_pragma_loop_numeric_value : Error<
> +  "invalid argument; expected a positive integer value">;
>
>  // Pragma unroll support.
>  def warn_pragma_unroll_cuda_value_in_parens : Warning<
> Index: include/clang/Basic/DiagnosticSemaKinds.td
> ===================================================================
> --- include/clang/Basic/DiagnosticSemaKinds.td (revision 214227)
> +++ include/clang/Basic/DiagnosticSemaKinds.td (working copy)
> @@ -541,8 +541,6 @@
>    "surrounding namespace with visibility attribute starts here">;
>  def err_pragma_loop_invalid_value : Error<
>    "invalid argument; expected a positive integer value">;
> -def err_pragma_loop_invalid_keyword : Error<
> -  "invalid argument; expected '%0' or 'disable'">;
>  def err_pragma_loop_compatibility : Error<
>    "%select{incompatible|duplicate}0 directives '%1' and '%2'">;
>  def err_pragma_loop_precedes_nonloop : Error<
> Index: include/clang/Parse/Parser.h
> ===================================================================
> --- include/clang/Parse/Parser.h (revision 214227)
> +++ include/clang/Parse/Parser.h (working copy)
> @@ -525,7 +525,7 @@
>
>    /// \brief Handle the annotation token produced for
>    /// #pragma clang loop and #pragma unroll.
> -  LoopHint HandlePragmaLoopHint();
> +  bool HandlePragmaLoopHint(LoopHint &);

Please name the parameter.

>
>    /// GetLookAheadToken - This peeks ahead N tokens and returns that token
>    /// without consuming any tokens.  LookAhead(0) returns 'Tok', LookAhead(1)
> Index: include/clang/Sema/LoopHint.h
> ===================================================================
> --- include/clang/Sema/LoopHint.h (revision 214227)
> +++ include/clang/Sema/LoopHint.h (working copy)
> @@ -29,11 +29,15 @@
>    // "#pragma unroll" and "#pragma nounroll" cases, this is identical to
>    // PragmaNameLoc.
>    IdentifierLoc *OptionLoc;
> -  // Identifier for the hint argument.  If null, then the hint has no argument
> -  // such as for "#pragma unroll".
> -  IdentifierLoc *ValueLoc;
> +  // Identifier for the hint state argument.  If null, then the state is
> +  // default value such as for "#pragma unroll".
> +  IdentifierLoc *StateLoc;
>    // Expression for the hint argument if it exists, null otherwise.
>    Expr *ValueExpr;
> +
> +  LoopHint()
> +      : PragmaNameLoc(nullptr), OptionLoc(nullptr), StateLoc(nullptr),
> +        ValueExpr(nullptr) {}
>  };
>
>  } // end namespace clang
> Index: lib/CodeGen/CGStmt.cpp
> ===================================================================
> --- lib/CodeGen/CGStmt.cpp (revision 214227)
> +++ lib/CodeGen/CGStmt.cpp (working copy)
> @@ -588,6 +588,7 @@
>        continue;
>
>      LoopHintAttr::OptionType Option = LH->getOption();
> +    int State = LH->getState();

Declaration shouldn't be an int; should be StateType (or whatever it
gets renamed to).

>      int ValueInt = LH->getValue();
>
>      const char *MetadataName;
> @@ -602,8 +603,8 @@
>        break;
>      case LoopHintAttr::Unroll:
>        // With the unroll loop hint, a non-zero value indicates full unrolling.
> -      MetadataName =
> -          ValueInt == 0 ? "llvm.loop.unroll.disable" : "llvm.loop.unroll.full";
> +      MetadataName = State == LoopHintAttr::Disable ? "llvm.loop.unroll.disable"
> +                                                    : "llvm.loop.unroll.full";
>        break;
>      case LoopHintAttr::UnrollCount:
>        MetadataName = "llvm.loop.unroll.count";
> @@ -614,7 +615,7 @@
>      switch (Option) {
>      case LoopHintAttr::Vectorize:
>      case LoopHintAttr::Interleave:
> -      if (ValueInt == 1) {
> +      if (State != LoopHintAttr::Disable) {
>          // FIXME: In the future I will modifiy the behavior of the metadata
>          // so we can enable/disable vectorization and interleaving separately.
>          Name = llvm::MDString::get(Context, "llvm.loop.vectorize.enable");
> Index: lib/Parse/ParsePragma.cpp
> ===================================================================
> --- lib/Parse/ParsePragma.cpp (revision 214227)
> +++ lib/Parse/ParsePragma.cpp (working copy)
> @@ -722,38 +722,62 @@
>    bool HasValue;
>  };
>
> -LoopHint Parser::HandlePragmaLoopHint() {
> +bool Parser::HandlePragmaLoopHint(LoopHint &Hint) {
>    assert(Tok.is(tok::annot_pragma_loop_hint));
>    PragmaLoopHintInfo *Info =
>        static_cast<PragmaLoopHintInfo *>(Tok.getAnnotationValue());
> +  ConsumeToken(); // The annotation token.
>
> -  LoopHint Hint;
> -  Hint.PragmaNameLoc =
> -      IdentifierLoc::create(Actions.Context, Info->PragmaName.getLocation(),
> -                            Info->PragmaName.getIdentifierInfo());
> -  Hint.OptionLoc =
> -      IdentifierLoc::create(Actions.Context, Info->Option.getLocation(),
> -                            Info->Option.getIdentifierInfo());
> -  if (Info->HasValue) {
> -    Hint.Range =
> -        SourceRange(Info->Option.getLocation(), Info->Value.getLocation());
> -    Hint.ValueLoc =
> -        IdentifierLoc::create(Actions.Context, Info->Value.getLocation(),
> -                              Info->Value.getIdentifierInfo());
> +  IdentifierInfo *PragmaNameInfo = Info->PragmaName.getIdentifierInfo();
> +  Hint.PragmaNameLoc = IdentifierLoc::create(
> +      Actions.Context, Info->PragmaName.getLocation(), PragmaNameInfo);
>
> +  IdentifierInfo *OptionInfo = Info->Option.getIdentifierInfo();
> +  Hint.OptionLoc = IdentifierLoc::create(
> +      Actions.Context, Info->Option.getLocation(), OptionInfo);
> +
> +  bool PragmaUnroll = PragmaNameInfo->getName() == "unroll";
> +  bool PragmaNoUnroll = PragmaNameInfo->getName() == "nounroll";
> +  if (!Info->HasValue && (PragmaUnroll | PragmaNoUnroll)) {

Please use || here instead of |.

> +    Hint.Range = SourceRange(Info->PragmaName.getLocation());

Pretty sure you don't need the explicit constructor call here.

> +    return true;
> +  }
> +
> +  bool StateOption = false;
> +  if (OptionInfo) // Pragma unroll does not specify an option.

It doesn't always specify an option, but it sometimes does (otherwise
there wouldn't be a .Case below).

> +    StateOption = llvm::StringSwitch<bool>(OptionInfo->getName())
> +                      .Case("vectorize", true)
> +                      .Case("interleave", true)
> +                      .Case("unroll", true)
> +                      .Default(false);
> +
> +  // Validate the argument.
> +  if (StateOption) {
> +    bool OptionUnroll = OptionInfo->isStr("unroll");
> +    SourceLocation StateLoc = Info->Value.getLocation();
> +    IdentifierInfo *StateInfo = Info->Value.getIdentifierInfo();
> +    if (!StateInfo || ((OptionUnroll ? !StateInfo->isStr("full")
> +                                     : !StateInfo->isStr("enable")) &&
> +                       !StateInfo->isStr("disable"))) {
> +      Diag(StateLoc, diag::err_pragma_invalid_keyword)
> +          << /*MissingArgument=*/false << /*FullKeyword=*/OptionUnroll;
> +      return false;
> +    }
> +    Hint.StateLoc = IdentifierLoc::create(Actions.Context, StateLoc, StateInfo);
> +  } else {
>      // FIXME: We should allow non-type template parameters for the loop hint
>      // value. See bug report #19610
>      if (Info->Value.is(tok::numeric_constant))
>        Hint.ValueExpr = Actions.ActOnNumericConstant(Info->Value).get();
> -    else
> -      Hint.ValueExpr = nullptr;
> -  } else {
> -    Hint.Range = SourceRange(Info->PragmaName.getLocation());
> -    Hint.ValueLoc = nullptr;
> -    Hint.ValueExpr = nullptr;
> +    else {
> +      Diag(Info->Value.getLocation(), diag::err_pragma_loop_numeric_value);
> +      return false;
> +    }
>    }
>
> -  return Hint;
> +  Hint.Range = SourceRange(Info->PragmaName.getLocation(),
> +                           Info->Value.getLocation());
> +  return true;
>  }
>
>  // #pragma GCC visibility comes in two variants:
> @@ -1755,12 +1779,10 @@
>  }
>
>  /// \brief Parses loop or unroll pragma hint value and fills in Info.
> -static bool ParseLoopHintValue(Preprocessor &PP, Token Tok, Token &PragmaName,
> -                               Token &Option, bool &ValueInParens,
> +static bool ParseLoopHintValue(Preprocessor &PP, Token &Tok, Token PragmaName,
> +                               Token Option, bool ValueInParens,
>                                 PragmaLoopHintInfo &Info) {
> -  ValueInParens = Tok.is(tok::l_paren);
>    if (ValueInParens) {
> -    PP.Lex(Tok);
>      if (Tok.is(tok::r_paren)) {
>        // Nothing between the parentheses.
>        std::string PragmaString;
> @@ -1784,13 +1806,15 @@
>
>    // FIXME: Value should be stored and parsed as a constant expression.
>    Token Value = Tok;
> +  PP.Lex(Tok);
>
>    if (ValueInParens) {
> -    PP.Lex(Tok);
> +    // Read ')'
>      if (Tok.isNot(tok::r_paren)) {
>        PP.Diag(Tok.getLocation(), diag::err_expected) << tok::r_paren;
>        return true;
>      }
> +    PP.Lex(Tok);
>    }
>
>    Info.PragmaName = PragmaName;
> @@ -1872,18 +1896,19 @@
>            << /*MissingOption=*/false << OptionInfo;
>        return;
>      }
> -
> -    auto *Info = new (PP.getPreprocessorAllocator()) PragmaLoopHintInfo;
>      PP.Lex(Tok);
> -    bool ValueInParens;
> -    if (ParseLoopHintValue(PP, Tok, PragmaName, Option, ValueInParens, *Info))
> -      return;
>
> -    if (!ValueInParens) {
> -      PP.Diag(Info->Value.getLocation(), diag::err_expected) << tok::l_paren;
> +    // Read '('
> +    if (Tok.isNot(tok::l_paren)) {
> +      PP.Diag(Tok.getLocation(), diag::err_expected) << tok::l_paren;
>        return;
>      }
> +    PP.Lex(Tok);
>
> +    auto *Info = new (PP.getPreprocessorAllocator()) PragmaLoopHintInfo;
> +    if (ParseLoopHintValue(PP, Tok, PragmaName, Option, /*ValueInParens=*/true, *Info))
> +      return;
> +
>      // Generate the loop hint token.
>      Token LoopHintTok;
>      LoopHintTok.startToken();
> @@ -1891,9 +1916,6 @@
>      LoopHintTok.setLocation(PragmaName.getLocation());
>      LoopHintTok.setAnnotationValue(static_cast<void *>(Info));
>      TokenList.push_back(LoopHintTok);
> -
> -    // Get next optimization option.
> -    PP.Lex(Tok);
>    }
>
>    if (Tok.isNot(tok::eod)) {
> @@ -1938,7 +1960,6 @@
>    if (Tok.is(tok::eod)) {
>      // nounroll or unroll pragma without an argument.
>      Info->PragmaName = PragmaName;
> -    Info->Option = PragmaName;
>      Info->HasValue = false;
>    } else if (PragmaName.getIdentifierInfo()->getName() == "nounroll") {
>      PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
> @@ -1947,9 +1968,12 @@
>    } else {
>      // Unroll pragma with an argument: "#pragma unroll N" or
>      // "#pragma unroll(N)".
> -    bool ValueInParens;
> -    if (ParseLoopHintValue(PP, Tok, PragmaName, PragmaName, ValueInParens,
> -                           *Info))
> +    // Read '(' if it exists.
> +    bool ValueInParens = Tok.is(tok::l_paren);
> +    if (ValueInParens)
> +      PP.Lex(Tok);
> +
> +    if (ParseLoopHintValue(PP, Tok, PragmaName, Token(), ValueInParens, *Info))
>        return;
>
>      // In CUDA, the argument to '#pragma unroll' should not be contained in
> @@ -1958,7 +1982,6 @@
>        PP.Diag(Info->Value.getLocation(),
>                diag::warn_pragma_unroll_cuda_value_in_parens);
>
> -    PP.Lex(Tok);
>      if (Tok.isNot(tok::eod)) {
>        PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
>            << "unroll";
> Index: lib/Parse/ParseStmt.cpp
> ===================================================================
> --- lib/Parse/ParseStmt.cpp (revision 214227)
> +++ lib/Parse/ParseStmt.cpp (working copy)
> @@ -1817,10 +1817,11 @@
>
>    // Get loop hints and consume annotated token.
>    while (Tok.is(tok::annot_pragma_loop_hint)) {
> -    LoopHint Hint = HandlePragmaLoopHint();
> -    ConsumeToken();
> +    LoopHint Hint;
> +    if (!HandlePragmaLoopHint(Hint))
> +      continue;
>
> -    ArgsUnion ArgHints[] = {Hint.PragmaNameLoc, Hint.OptionLoc, Hint.ValueLoc,
> +    ArgsUnion ArgHints[] = {Hint.PragmaNameLoc, Hint.OptionLoc, Hint.StateLoc,
>                              ArgsUnion(Hint.ValueExpr)};
>      TempAttrs.addNew(Hint.PragmaNameLoc->Ident, Hint.Range, nullptr,
>                       Hint.PragmaNameLoc->Loc, ArgHints, 4,
> Index: lib/Sema/SemaStmtAttr.cpp
> ===================================================================
> --- lib/Sema/SemaStmtAttr.cpp (revision 214227)
> +++ lib/Sema/SemaStmtAttr.cpp (working copy)
> @@ -47,13 +47,11 @@
>                                  SourceRange) {
>    IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
>    IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
> -  IdentifierInfo *OptionInfo = OptionLoc->Ident;
> -  IdentifierLoc *ValueLoc = A.getArgAsIdent(2);
> -  IdentifierInfo *ValueInfo = ValueLoc ? ValueLoc->Ident : nullptr;
> +  IdentifierLoc *StateLoc = A.getArgAsIdent(2);
>    Expr *ValueExpr = A.getArgAsExpr(3);
>
> -  assert(OptionInfo && "Attribute must have valid option info.");
> -
> +  bool PragmaUnroll = PragmaNameLoc->Ident->getName() == "unroll";
> +  bool PragmaNoUnroll = PragmaNameLoc->Ident->getName() == "nounroll";
>    if (St->getStmtClass() != Stmt::DoStmtClass &&
>        St->getStmtClass() != Stmt::ForStmtClass &&
>        St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
> @@ -69,13 +67,16 @@
>
>    LoopHintAttr::OptionType Option;
>    LoopHintAttr::Spelling Spelling;
> -  if (PragmaNameLoc->Ident->getName() == "unroll") {
> -    Option = ValueLoc ? LoopHintAttr::UnrollCount : LoopHintAttr::Unroll;
> +  if (PragmaUnroll) {
> +    Option = ValueExpr ? LoopHintAttr::UnrollCount : LoopHintAttr::Unroll;
>      Spelling = LoopHintAttr::Pragma_unroll;
> -  } else if (PragmaNameLoc->Ident->getName() == "nounroll") {
> +  } else if (PragmaNoUnroll) {
>      Option = LoopHintAttr::Unroll;
>      Spelling = LoopHintAttr::Pragma_nounroll;
>    } else {
> +    assert(OptionLoc && OptionLoc->Ident &&
> +           "Attribute must have valid option info.");
> +    IdentifierInfo *OptionInfo = OptionLoc->Ident;
>      Option = llvm::StringSwitch<LoopHintAttr::OptionType>(OptionInfo->getName())
>                   .Case("vectorize", LoopHintAttr::Vectorize)
>                   .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
> @@ -87,35 +88,10 @@
>      Spelling = LoopHintAttr::Pragma_clang_loop;
>    }
>
> -  int ValueInt = -1;
> -  if (Option == LoopHintAttr::Unroll &&
> -      Spelling == LoopHintAttr::Pragma_unroll) {
> -    if (ValueInfo)
> -      ValueInt = (ValueInfo->isStr("disable") ? 0 : 1);
> -  } else if (Option == LoopHintAttr::Unroll &&
> -             Spelling == LoopHintAttr::Pragma_nounroll) {
> -    ValueInt = 0;
> -  } else if (Option == LoopHintAttr::Vectorize ||
> -             Option == LoopHintAttr::Interleave ||
> -             Option == LoopHintAttr::Unroll) {
> -    // Unrolling uses the keyword "full" rather than "enable" to indicate full
> -    // unrolling.
> -    const char *TrueKeyword =
> -        Option == LoopHintAttr::Unroll ? "full" : "enable";
> -    if (!ValueInfo) {
> -      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_keyword)
> -          << TrueKeyword;
> -      return nullptr;
> -    }
> -    if (ValueInfo->isStr("disable"))
> -      ValueInt = 0;
> -    else if (ValueInfo->getName() == TrueKeyword)
> -      ValueInt = 1;
> -    else {
> -      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_keyword)
> -          << TrueKeyword;
> -      return nullptr;
> -    }
> +  int ValueInt = 1;
> +  LoopHintAttr::StateType State = LoopHintAttr::Default;
> +  if (PragmaNoUnroll) {
> +    State = LoopHintAttr::Disable;
>    } else if (Option == LoopHintAttr::VectorizeWidth ||
>               Option == LoopHintAttr::InterleaveCount ||
>               Option == LoopHintAttr::UnrollCount) {
> @@ -124,28 +100,39 @@
>      llvm::APSInt ValueAPS;
>      if (!ValueExpr || !ValueExpr->isIntegerConstantExpr(ValueAPS, S.Context) ||
>          (ValueInt = ValueAPS.getSExtValue()) < 1) {
> -      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_value);
> +      S.Diag(A.getRange().getEnd(), diag::err_pragma_loop_invalid_value);

A.getLoc() instead of A.getRange().getEnd()?

>        return nullptr;
>      }
> -  } else
> -    llvm_unreachable("Unknown loop hint option");
> +  } else if (Option == LoopHintAttr::Vectorize ||
> +             Option == LoopHintAttr::Interleave ||
> +             Option == LoopHintAttr::Unroll) {
> +    // Default state is assumed if StateLoc is not specified, such as with
> +    // '#pragma unroll'.
> +    if (StateLoc && StateLoc->Ident) {
> +      if (StateLoc->Ident->isStr("disable"))
> +        State = LoopHintAttr::Disable;
> +      else
> +        State = LoopHintAttr::Enable;
> +    }
> +  }
>
> -  return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, ValueInt,
> -                                      A.getRange());
> +  return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
> +                                      ValueInt, A.getRange());
>  }
>
> -static void CheckForIncompatibleAttributes(
> -    Sema &S, const SmallVectorImpl<const Attr *> &Attrs) {
> -  // There are 3 categories of loop hints attributes: vectorize, interleave, and
> -  // unroll. Each comes in two variants: a boolean form and a numeric form.  The
> -  // boolean hints selectively enables/disables the transformation for the loop
> -  // (for unroll, a nonzero value indicates full unrolling rather than enabling
> -  // the transformation).  The numeric hint provides an integer hint (for
> -  // example, unroll count) to the transformer. The following array accumulates
> -  // the hints encountered while iterating through the attributes to check for
> -  // compatibility.
> +static void
> +CheckForIncompatibleAttributes(Sema &S,
> +                               const SmallVectorImpl<const Attr *> &Attrs) {
> +  // There are 3 categories of loop hints attributes: vectorize, interleave,
> +  // and unroll. Each comes in two variants: a state form and a numeric form.
> +  // The state form selectively defaults/enables/disables the transformation
> +  // for the loop (for unroll, default indicates full unrolling rather than
> +  // enabling the transformation).  The numeric form form provides an integer
> +  // hint (for example, unroll count) to the transformer. The following array
> +  // accumulates the hints encountered while iterating through the attributes
> +  // to check for compatibility.
>    struct {
> -    const LoopHintAttr *EnableAttr;
> +    const LoopHintAttr *StateAttr;
>      const LoopHintAttr *NumericAttr;
>    } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
>
> @@ -179,8 +166,8 @@
>      if (Option == LoopHintAttr::Vectorize ||
>          Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
>        // Enable|disable hint.  For example, vectorize(enable).
> -      PrevAttr = CategoryState.EnableAttr;
> -      CategoryState.EnableAttr = LH;
> +      PrevAttr = CategoryState.StateAttr;
> +      CategoryState.StateAttr = LH;
>      } else {
>        // Numeric hint.  For example, vectorize_width(8).
>        PrevAttr = CategoryState.NumericAttr;
> @@ -195,14 +182,15 @@
>            << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
>            << LH->getDiagnosticName(Policy);
>
> -    if (CategoryState.EnableAttr && CategoryState.NumericAttr &&
> -        (Category == Unroll || !CategoryState.EnableAttr->getValue())) {
> +    if (CategoryState.StateAttr && CategoryState.NumericAttr &&
> +        (Category == Unroll ||
> +         CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
>        // Disable hints are not compatible with numeric hints of the same
>        // category.  As a special case, numeric unroll hints are also not
>        // compatible with "enable" form of the unroll pragma, unroll(full).
>        S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
>            << /*Duplicate=*/false
> -          << CategoryState.EnableAttr->getDiagnosticName(Policy)
> +          << CategoryState.StateAttr->getDiagnosticName(Policy)
>            << CategoryState.NumericAttr->getDiagnosticName(Policy);
>      }
>    }
>

~Aaron




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