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[BPF] Restrict preserve_access_index attribute to C only 

This patch is a follow-up for commit 4e2ce228ae
  [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
This commit is contained in:
Yonghong Song 2019-11-14 10:34:35 -08:00
parent 4c39f34199
commit dd16b3fe25
3 changed files with 21 additions and 30 deletions
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1
clang/include/clang/Basic/Attr.td
View File

@ -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,

41
clang/lib/CodeGen/CGExpr.cpp
View File

@ -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 Expr *E = ArrayBase->IgnoreImpCasts();
if (const auto *ME = dyn_cast<MemberExpr>(E))
return ME->getMemberDecl()->hasAttr<BPFPreserveAccessIndexAttr>();
const auto *DeclRefCast = dyn_cast<DeclRefExpr>(E);
if (DeclRefCast) {
const VarDecl *VarDef = dyn_cast<VarDecl>(DeclRefCast->getDecl());
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;
return RecT->getDecl()->hasAttr<BPFPreserveAccessIndexAttr>();
const auto *PointeeT = PtrT->getPointeeType()
->getUnqualifiedDesugaredType();
if (const auto *RecT = dyn_cast<RecordType>(PointeeT))
return RecT->getDecl()->hasAttr<BPFPreserveAccessIndexAttr>();
return false;
}
return false;

9
clang/test/Sema/bpf-attr-preserve-access-index.cpp Normal file
View File

@ -0,0 +1,9 @@
// 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}}