Pretty up the emission of field l-values and use volatile and TBAA when
loading references as part of that. Use 'char' TBAA when accessing
(immediate!) fields of a may_alias struct; fixes PR9307.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126540 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 5d69aad..2abaadf 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1610,39 +1610,67 @@
}
}
-LValue CodeGenFunction::EmitLValueForField(llvm::Value *BaseValue,
- const FieldDecl *Field,
- unsigned CVRQualifiers) {
- if (Field->isBitField())
- return EmitLValueForBitfield(BaseValue, Field, CVRQualifiers);
+LValue CodeGenFunction::EmitLValueForField(llvm::Value *baseAddr,
+ const FieldDecl *field,
+ unsigned cvr) {
+ if (field->isBitField())
+ return EmitLValueForBitfield(baseAddr, field, cvr);
- const CGRecordLayout &RL =
- CGM.getTypes().getCGRecordLayout(Field->getParent());
- unsigned idx = RL.getLLVMFieldNo(Field);
- llvm::Value *V = Builder.CreateStructGEP(BaseValue, idx, "tmp");
+ const RecordDecl *rec = field->getParent();
+ QualType type = field->getType();
- // Match union field type.
- if (Field->getParent()->isUnion()) {
- const llvm::Type *FieldTy =
- CGM.getTypes().ConvertTypeForMem(Field->getType());
- const llvm::PointerType *BaseTy =
- cast<llvm::PointerType>(BaseValue->getType());
- unsigned AS = BaseTy->getAddressSpace();
- V = Builder.CreateBitCast(V,
- llvm::PointerType::get(FieldTy, AS),
- "tmp");
+ bool mayAlias = rec->hasAttr<MayAliasAttr>();
+
+ llvm::Value *addr;
+ if (rec->isUnion()) {
+ // For unions, we just cast to the appropriate type.
+ assert(!type->isReferenceType() && "union has reference member");
+
+ const llvm::Type *llvmType = CGM.getTypes().ConvertTypeForMem(type);
+ unsigned AS =
+ cast<llvm::PointerType>(baseAddr->getType())->getAddressSpace();
+ addr = Builder.CreateBitCast(baseAddr, llvmType->getPointerTo(AS),
+ field->getName());
+ } else {
+ // For structs, we GEP to the field that the record layout suggests.
+ unsigned idx = CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
+ addr = Builder.CreateStructGEP(baseAddr, idx, field->getName());
+
+ // If this is a reference field, load the reference right now.
+ if (const ReferenceType *refType = type->getAs<ReferenceType>()) {
+ llvm::LoadInst *load = Builder.CreateLoad(addr, "ref");
+ if (cvr & Qualifiers::Volatile) load->setVolatile(true);
+
+ if (CGM.shouldUseTBAA()) {
+ llvm::MDNode *tbaa;
+ if (mayAlias)
+ tbaa = CGM.getTBAAInfo(getContext().CharTy);
+ else
+ tbaa = CGM.getTBAAInfo(type);
+ CGM.DecorateInstruction(load, tbaa);
+ }
+
+ addr = load;
+ mayAlias = false;
+ type = refType->getPointeeType();
+ cvr = 0; // qualifiers don't recursively apply to referencee
+ }
}
- if (Field->getType()->isReferenceType())
- V = Builder.CreateLoad(V, "tmp");
- unsigned Alignment = getContext().getDeclAlign(Field).getQuantity();
- LValue LV = MakeAddrLValue(V, Field->getType(), Alignment);
- LV.getQuals().addCVRQualifiers(CVRQualifiers);
+ unsigned alignment = getContext().getDeclAlign(field).getQuantity();
+ LValue LV = MakeAddrLValue(addr, type, alignment);
+ LV.getQuals().addCVRQualifiers(cvr);
// __weak attribute on a field is ignored.
if (LV.getQuals().getObjCGCAttr() == Qualifiers::Weak)
LV.getQuals().removeObjCGCAttr();
-
+
+ // Fields of may_alias structs act like 'char' for TBAA purposes.
+ // FIXME: this should get propagated down through anonymous structs
+ // and unions.
+ if (mayAlias && LV.getTBAAInfo())
+ LV.setTBAAInfo(CGM.getTBAAInfo(getContext().CharTy));
+
return LV;
}