1 files changed, 68 insertions, 7 deletions

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 99406715cbf..e32db8c56df 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3402,11 +3402,67 @@ static QualType getFixedSizeElementType(const ASTContext &ctx,
   return eltType;
 }
 
+/// Given an array base, check whether its member access belongs to a record
+/// with preserve_access_index attribute or not.
+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]; };
+  //    struct s *p;
+  //    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());
+    if (!VarDef)
+      return false;
+
+    const auto *PtrT = dyn_cast<PointerType>(VarDef->getType().getTypePtr());
+    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>();
+  }
+
+  return false;
+}
+
 static Address emitArraySubscriptGEP(CodeGenFunction &CGF, Address addr,
                                      ArrayRef<llvm::Value *> indices,
                                      QualType eltType, bool inbounds,
                                      bool signedIndices, SourceLocation loc,
                                      QualType *arrayType = nullptr,
+                                     const Expr *Base = nullptr,
                                      const llvm::Twine &name = "arrayidx") {
   // All the indices except that last must be zero.
 #ifndef NDEBUG
@@ -3428,7 +3484,8 @@ static Address emitArraySubscriptGEP(CodeGenFunction &CGF, Address addr,
 
   llvm::Value *eltPtr;
   auto LastIndex = dyn_cast<llvm::ConstantInt>(indices.back());
-  if (!CGF.IsInPreservedAIRegion || !LastIndex) {
+  if (!LastIndex ||
+      (!CGF.IsInPreservedAIRegion && !IsPreserveAIArrayBase(CGF, Base))) {
     eltPtr = emitArraySubscriptGEP(
         CGF, addr.getPointer(), indices, inbounds, signedIndices,
         loc, name);
@@ -3582,7 +3639,7 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
     Addr = emitArraySubscriptGEP(
         *this, ArrayLV.getAddress(), {CGM.getSize(CharUnits::Zero()), Idx},
         E->getType(), !getLangOpts().isSignedOverflowDefined(), SignedIndices,
-        E->getExprLoc(), &arrayType);
+        E->getExprLoc(), &arrayType, E->getBase());
     EltBaseInfo = ArrayLV.getBaseInfo();
     EltTBAAInfo = CGM.getTBAAInfoForSubobject(ArrayLV, E->getType());
   } else {
@@ -3592,7 +3649,8 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
     QualType ptrType = E->getBase()->getType();
     Addr = emitArraySubscriptGEP(*this, Addr, Idx, E->getType(),
                                  !getLangOpts().isSignedOverflowDefined(),
-                                 SignedIndices, E->getExprLoc(), &ptrType);
+                                 SignedIndices, E->getExprLoc(), &ptrType,
+                                 E->getBase());
   }
 
   LValue LV = MakeAddrLValue(Addr, E->getType(), EltBaseInfo, EltTBAAInfo);
@@ -3993,12 +4051,13 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
     const CGBitFieldInfo &Info = RL.getBitFieldInfo(field);
     Address Addr = base.getAddress();
     unsigned Idx = RL.getLLVMFieldNo(field);
-    if (!IsInPreservedAIRegion) {
+    const RecordDecl *rec = field->getParent();
+    if (!IsInPreservedAIRegion &&
+        (!getDebugInfo() || !rec->hasAttr<BPFPreserveAccessIndexAttr>())) {
       if (Idx != 0)
         // For structs, we GEP to the field that the record layout suggests.
         Addr = Builder.CreateStructGEP(Addr, Idx, field->getName());
     } else {
-      const RecordDecl *rec = field->getParent();
       llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateRecordType(
           getContext().getRecordType(rec), rec->getLocation());
       Addr = Builder.CreatePreserveStructAccessIndex(Addr, Idx,
@@ -4081,7 +4140,8 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
       addr = Address(Builder.CreateLaunderInvariantGroup(addr.getPointer()),
                      addr.getAlignment());
 
-    if (IsInPreservedAIRegion) {
+    if (IsInPreservedAIRegion ||
+        (getDebugInfo() && rec->hasAttr<BPFPreserveAccessIndexAttr>())) {
       // Remember the original union field index
       llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateRecordType(
           getContext().getRecordType(rec), rec->getLocation());
@@ -4095,7 +4155,8 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
       addr = Builder.CreateElementBitCast(
           addr, CGM.getTypes().ConvertTypeForMem(FieldType), field->getName());
   } else {
-    if (!IsInPreservedAIRegion)
+    if (!IsInPreservedAIRegion &&
+        (!getDebugInfo() || !rec->hasAttr<BPFPreserveAccessIndexAttr>()))
       // For structs, we GEP to the field that the record layout suggests.
       addr = emitAddrOfFieldStorage(*this, addr, field);
     else