Commit dd16b3fe authored by Yonghong Song's avatar Yonghong Song
Browse files

[BPF] Restrict preserve_access_index attribute to C only 

This patch is a follow-up for commit 4e2ce228
  [BPF] Add preserve_access_index attribute for record definition
to restrict attribute for C only. A new test case is added
to check for this restriction.

Additional code polishing is done based on
Aaron Ballman's suggestion in https://reviews.llvm.org/D69759/new/.

Differential Revision: https://reviews.llvm.org/D70257
parent 4c39f341

clang/include/clang/Basic/Attr.td

+1 −0
Original line number Diff line number Diff line
@@ -1584,6 +1584,7 @@ def BPFPreserveAccessIndex : InheritableAttr, 
  let Spellings = [Clang<"preserve_access_index">];

  let Subjects = SubjectList<[Record], ErrorDiag>;

  let Documentation = [BPFPreserveAccessIndexDocs];

  let LangOpts = [COnly];

}



def WebAssemblyImportModule : InheritableAttr,

clang/lib/CodeGen/CGExpr.cpp

+12 −31
Original line number Diff line number Diff line
@@ -3408,10 +3408,6 @@ static bool IsPreserveAIArrayBase(CodeGenFunction &CGF, const Expr *ArrayBase) { 
  if (!ArrayBase || !CGF.getDebugInfo())

    return false;



  const auto *ImplicitCast = dyn_cast<ImplicitCastExpr>(ArrayBase);

  if (!ImplicitCast)

    return false;



  // Only support base as either a MemberExpr or DeclRefExpr.

  // DeclRefExpr to cover cases like:

  //    struct s { int a; int b[10]; };
@@ -3419,39 +3415,24 @@ static bool IsPreserveAIArrayBase(CodeGenFunction &CGF, const Expr *ArrayBase) { 
  //    p[1].a

  // p[1] will generate a DeclRefExpr and p[1].a is a MemberExpr.

  // p->b[5] is a MemberExpr example.

  const Expr *E = ImplicitCast->getSubExpr();

  const auto *MemberCast = dyn_cast<MemberExpr>(E);

  if (MemberCast)

    return MemberCast->getMemberDecl()->hasAttr<BPFPreserveAccessIndexAttr>();



  const auto *DeclRefCast = dyn_cast<DeclRefExpr>(E);

  if (DeclRefCast) {

    const VarDecl *VarDef = dyn_cast<VarDecl>(DeclRefCast->getDecl());

  const Expr *E = ArrayBase->IgnoreImpCasts();

  if (const auto *ME = dyn_cast<MemberExpr>(E))

    return ME->getMemberDecl()->hasAttr<BPFPreserveAccessIndexAttr>();



  if (const auto *DRE = dyn_cast<DeclRefExpr>(E)) {

    const auto *VarDef = dyn_cast<VarDecl>(DRE->getDecl());

    if (!VarDef)

      return false;



    const auto *PtrT = dyn_cast<PointerType>(VarDef->getType().getTypePtr());

    const auto *PtrT = VarDef->getType()->getAs<PointerType>();

    if (!PtrT)

      return false;

    const auto *PointeeT = PtrT->getPointeeType().getTypePtr();



    // Peel off typedef's

    const auto *TypedefT = dyn_cast<TypedefType>(PointeeT);

    while (TypedefT) {

      PointeeT = TypedefT->desugar().getTypePtr();

      TypedefT = dyn_cast<TypedefType>(PointeeT);

    }



    // Not a typedef any more, it should be an elaborated type.

    const auto ElaborateT = dyn_cast<ElaboratedType>(PointeeT);

    if (!ElaborateT)

      return false;



    const auto *RecT = dyn_cast<RecordType>(ElaborateT->desugar().getTypePtr());

    if (!RecT)

      return false;



    const auto *PointeeT = PtrT->getPointeeType()

                             ->getUnqualifiedDesugaredType();

    if (const auto *RecT = dyn_cast<RecordType>(PointeeT))

      return RecT->getDecl()->hasAttr<BPFPreserveAccessIndexAttr>();

    return false;

  }



  return false;

clang/test/Sema/bpf-attr-preserve-access-index.cpp

0 → 100644
+9 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -x c++ -triple bpf-pc-linux-gnu -dwarf-version=4 -fsyntax-only -verify %s



#define __reloc__ __attribute__((preserve_access_index))



struct t1 {

  int a;

  int b[4];

  int c:1;

} __reloc__; // expected-warning {{'preserve_access_index' attribute ignored}}