lib/Sema/SemaStmtAttr.cpp

//===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements stmt-related attribute processing.
//
//===----------------------------------------------------------------------===//

#include "clang/Sema/SemaInternal.h"
#include "clang/AST/ASTContext.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/LoopHint.h"
#include "clang/Sema/ScopeInfo.h"
#include "llvm/ADT/StringExtras.h"

using namespace clang;
using namespace sema;

static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const AttributeList &A,
                                   SourceRange Range) {
  if (!isa<NullStmt>(St)) {
    S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
        << St->getLocStart();
    if (isa<SwitchCase>(St)) {
      SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
      S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
          << FixItHint::CreateInsertion(L, ";");
    }
    return nullptr;
  }
  if (S.getCurFunction()->SwitchStack.empty()) {
    S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
    return nullptr;
  }
  return ::new (S.Context) FallThroughAttr(A.getRange(), S.Context,
                                           A.getAttributeSpellingListIndex());
}

static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const AttributeList &A,
                                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;
  Expr *ValueExpr = A.getArgAsExpr(3);

  assert(OptionInfo && "Attribute must have valid option info.");

  if (St->getStmtClass() != Stmt::DoStmtClass &&
      St->getStmtClass() != Stmt::ForStmtClass &&
      St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
      St->getStmtClass() != Stmt::WhileStmtClass) {
    const char *Pragma = PragmaNameLoc->Ident->getName() == "unroll"
                             ? "#pragma unroll"
                             : "#pragma clang loop";
    S.Diag(St->getLocStart(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
    return nullptr;
  }

  LoopHintAttr::OptionType Option;
  LoopHintAttr::Spelling Spelling;
  if (PragmaNameLoc->Ident->getName() == "unroll") {
    Option = ValueLoc ? LoopHintAttr::UnrollCount : LoopHintAttr::Unroll;
    Spelling = LoopHintAttr::Pragma_unroll;
  } else {
    Option = llvm::StringSwitch<LoopHintAttr::OptionType>(OptionInfo->getName())
                 .Case("vectorize", LoopHintAttr::Vectorize)
                 .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
                 .Case("interleave", LoopHintAttr::Interleave)
                 .Case("interleave_count", LoopHintAttr::InterleaveCount)
                 .Case("unroll", LoopHintAttr::Unroll)
                 .Case("unroll_count", LoopHintAttr::UnrollCount)
                 .Default(LoopHintAttr::Vectorize);
    Spelling = LoopHintAttr::Pragma_clang_loop;
  }

  int ValueInt;
  if (Option == LoopHintAttr::Unroll &&
      Spelling == LoopHintAttr::Pragma_unroll) {
    ValueInt = 1;
  } else if (Option == LoopHintAttr::Vectorize ||
             Option == LoopHintAttr::Interleave ||
             Option == LoopHintAttr::Unroll) {
    if (!ValueInfo) {
      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_keyword);
      return nullptr;
    }
    if (ValueInfo->isStr("disable"))
      ValueInt = 0;
    else if (ValueInfo->isStr("enable"))
      ValueInt = 1;
    else {
      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_keyword);
      return nullptr;
    }
  } else if (Option == LoopHintAttr::VectorizeWidth ||
             Option == LoopHintAttr::InterleaveCount ||
             Option == LoopHintAttr::UnrollCount) {
    // FIXME: We should support template parameters for the loop hint value.
    // See bug report #19610.
    llvm::APSInt ValueAPS;
    if (!ValueExpr || !ValueExpr->isIntegerConstantExpr(ValueAPS, S.Context) ||
        (ValueInt = ValueAPS.getSExtValue()) < 1) {
      S.Diag(ValueLoc->Loc, diag::err_pragma_loop_invalid_value);
      return nullptr;
    }
  } else
    llvm_unreachable("Unknown loop hint option");

  return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, ValueInt,
                                      A.getRange());
}

static void CheckForIncompatibleAttributes(
    Sema &S, const SmallVectorImpl<const Attr *> &Attrs) {
  // There are 3 categories of loop hints: vectorize, interleave, and
  // unroll. Each comes in two variants: an enable/disable form and a
  // form which takes a numeric argument. For example:
  // unroll(enable|disable) and unroll_count(N). The following array
  // accumulate the hints encountered while iterating through the
  // attributes to check for compatibility.
  struct {
    const LoopHintAttr *EnableAttr;
    const LoopHintAttr *NumericAttr;
  } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};

  for (const auto *I : Attrs) {
    const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);

    // Skip non loop hint attributes
    if (!LH)
      continue;

    int Option = LH->getOption();
    int Category;
    switch (Option) {
    case LoopHintAttr::Vectorize:
    case LoopHintAttr::VectorizeWidth:
      Category = 0;
      break;
    case LoopHintAttr::Interleave:
    case LoopHintAttr::InterleaveCount:
      Category = 1;
      break;
    case LoopHintAttr::Unroll:
    case LoopHintAttr::UnrollCount:
      Category = 2;
      break;
    };

    auto &CategoryState = HintAttrs[Category];
    SourceLocation OptionLoc = LH->getRange().getBegin();
    const LoopHintAttr *PrevAttr;
    if (Option == LoopHintAttr::Vectorize ||
        Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
      // Enable|disable hint.  For example, vectorize(enable).
      PrevAttr = CategoryState.EnableAttr;
      CategoryState.EnableAttr = LH;
    } else {
      // Numeric hint.  For example, vectorize_width(8).
      PrevAttr = CategoryState.NumericAttr;
      CategoryState.NumericAttr = LH;
    }

    if (PrevAttr)
      // Cannot specify same type of attribute twice.
      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
          << /*Duplicate=*/true << PrevAttr->getDiagnosticName()
          << LH->getDiagnosticName();

    if (CategoryState.EnableAttr && !CategoryState.EnableAttr->getValue() &&
        CategoryState.NumericAttr) {
      // Disable hints are not compatible with numeric hints of the
      // same category.
      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
          << /*Duplicate=*/false
          << CategoryState.EnableAttr->getDiagnosticName()
          << CategoryState.NumericAttr->getDiagnosticName();
    }
  }
}

static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
                                  SourceRange Range) {
  switch (A.getKind()) {
  case AttributeList::UnknownAttribute:
    S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
           diag::warn_unhandled_ms_attribute_ignored :
           diag::warn_unknown_attribute_ignored) << A.getName();
    return nullptr;
  case AttributeList::AT_FallThrough:
    return handleFallThroughAttr(S, St, A, Range);
  case AttributeList::AT_LoopHint:
    return handleLoopHintAttr(S, St, A, Range);
  default:
    // if we're here, then we parsed a known attribute, but didn't recognize
    // it as a statement attribute => it is declaration attribute
    S.Diag(A.getRange().getBegin(), diag::err_attribute_invalid_on_stmt)
        << A.getName() << St->getLocStart();
    return nullptr;
  }
}

StmtResult Sema::ProcessStmtAttributes(Stmt *S, AttributeList *AttrList,
                                       SourceRange Range) {
  SmallVector<const Attr*, 8> Attrs;
  for (const AttributeList* l = AttrList; l; l = l->getNext()) {
    if (Attr *a = ProcessStmtAttribute(*this, S, *l, Range))
      Attrs.push_back(a);
  }

  CheckForIncompatibleAttributes(*this, Attrs);

  if (Attrs.empty())
    return S;

  return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
}